Are you ready to be a test pilot?

[rv6ejguy]

Oh boy, where do I start.

Automobile engines may be of a higher technical level than a Lycoming, but they are NOT superior when it comes to driving an airplane through the sky. Take a look at the main crank bearings and the engine block of a Subaru and compare them to the Lyc. When you are swinging the weight of the prop out front, it requires some hefty support. Lyc's also deliver peak power at low RPM, while the Subies need to scream along at much high RPM to deliver peak horsepower, hence the gear reduction units. I contend that automobile engines are very poor airplane engines because they need to be jerryrigged to make them work.



The benefit they have is that they are cheap because they are mass produced. Can't beat that. They also have great reliability when used for their intended and designed use. Start sticking them in airplanes and you are bringing along a whole additional set of engineering problems to be solved. I don't know any engine engineer that thinks gear reduction units are the best way to turn a prop. No, it's just a band-aide stuck on an engineering problem that otherwise, can't be fixed.



The whole 100LL thing has become the enabling battle cry of the alternate engine groupies. Unfortunately, it doesn't hold water. No one is going to wake up one moring to find that hundreds of thousands of engines that use the product suddenly are silent because no one is making it any longer. I don't doubt that there will be a transition to other fuels in the long run. That's probably why the diesel engine is looking like a viable engine alternative. But you and I will be able to buy 100LL for many, many years to come. Now the price of that gallon of 100LL may be another issue.



Finally, the reason I fly a homebuilt and not a Cessna 150 is because I can upgrade my Lycosaur with electronic ignition, FADEC, etc and get the best of both worlds----newer features and capabilities with proven reliability.

Oops, screwed up the quote in the last post there:

I fly a Sube and rebuilt the engine myself being a racecar engine builder by profession. The engineering, metallurgy, choice of materials, machining and balance of the Sube is far superior to anything seen in a Lyc. I have never heard of a bottom end failure on the EJ series Subes. There is no doubt that they can take much higher continuous stress. This was proven by their wide open run : http://www.subaru-global.com/about/history/1989-001.html#subhead-001

Anyone who thinks that modern auto engines are not capable of spinning at 4500 rpm all day, all month, all year long is simply ill-informed. I built and road raced Japanese engined cars for 13 years making over 5 times their naturally aspirated stock power and running them 2500 rpm over the stock redline. Not one ever suffered a catastophic failure.

What is this? Every Pratt, Wright, Allison, and Merlin had a reduction gear. You call that a band-aid?

My Sube runs on 100LL just fine or 91 octane if I choose.

Proven? Every 24 hours, there are more high speed hours put on cars running in Germany alone, than all the Lycoming engines ever built have accumulated in the last decade. For every hour that Lycs have, cars have accumulated millions of hours. You don't think Lycs break? Better brush up on those accident reports. There are plenty of fatals caused by catastrophic failures and don't forget the class action suits brought against Lyc and their turbocharged 540s where dozens blew up or went only a fraction of the time to TBO. Let's not forget the recent judgement against Lyc for the crank problems and all the other problems these "proven designs" have suffered in the last 5-6 years. This is a joke when you are paying $30,00+.

Some might find this interesting: http://www.sdsefi.com/air7.html

 

[Jconard]

Having road raced in open wheel cars for 13 years....

1. An airplane engine only has to be efficient within a very narrow RPM band 2-2.5K rpm, which makes most of the advanced control systems on a car unnecessary.

2. A racing engine also has to respond smoothly and instantly to throttle changes, which an airplane engine really does not have to...I know what people are thinking..."going around", but that is not the kind of response needed from a race engine coming out of a corner..modulation is the ey to the race engine. The net is that there too are all sorts of demands and systems not needed.

3. The racing engine does not experience anywhere near the torsional stress impsed on an airplane from the 7-foot diameter 60lb flywheel, which is the prop.

4. Within the application of a 500 rpm operation spread, almost constant speed operation, mechanical fuel injection and fixed timing are elegant and do not loose much.

5. The cranks in a sube are tiny, perfect for changing rpm all the time, but no dampening mass for constant running.

6. Liquid cooling is unnecesary, adds weight, and complexity. Aircooling works great when it is freezing, it works great when it is hot, it is simply and light.

Recently an H-6 RV-7 subaru pilot posted speeds and fuel burns from his plane. They were amazingly slow and high, given all the claims.

For example: at 8500 ft

RPM 2200/3970
BURN = 8.6
TAS = 141 (162)
MPG = 18.83

This is about ten knots slower and the same fuel burn as a 160hp lycoming rv7a I know got with no wheel or leg fairings. It will be about 100lbs heavier, and have no provision for a hydrolic prop.

With all the superiority, it makes you wonder where the performance is...

 

[f1rocket]

There is no doubt that they can take much higher continuous stress. This was proven by their wide open run : http://www.subaru-global.com/about/history/1989-001.html#subhead-001

I'm sorry, but there is plenty of doubt. There is absolutely no track record of this engine performing in an aviation environment. Talk to me in ten years.

Anyone who thinks that modern auto engines are not capable of spinning at 4500 rpm all day, all month, all year long is simply ill-informed. I built and road raced Japanese engined cars for 13 years making over 5 times their naturally aspirated stock power and running them 2500 rpm over the stock redline. Not one ever suffered a catastophic failure.

Was it swinging a 70 lb prop at varying density altitudes and temperatures? If not, then the facts are irrelevant when it comes to using them as aviation engines. Anyone who thinks just because an automobile engine can rev at 4500 RPM on a test stand for months at a time, this makes it suitable for use in an airplane is not only ill-informed, but seriously under-estimating the engineering difficulties of adapting automobile engines for aviation usage. If it was easy, everyone would have already done it.

What is this? Every Pratt, Wright, Allison, and Merlin had a reduction gear. You call that a band-aid?

For the most part, yes. This was the fastest way to adapt these engines to their relative airframes during the war, where getting the thing into the theater of war was more important than elegant engineering solutions. I know of no engineer that thinks adding more moving parts, more complexity, more friction, is a better solution than a direct-drive engine. It does have it's application in very specific engineering solutions, but for the most part, it is to be avoided if possible.

Proven? Every 24 hours, there are more high speed hours put on cars running in Germany alone, than all the Lycoming engines ever built have accumulated in the last decade. For every hour that Lycs have, cars have accumulated millions of hours. You don't think Lycs break? Better brush up on those accident reports. There are plenty of fatals caused by catastrophic failures and don't forget the class action suits brought against Lyc and their turbocharged 540s where dozens blew up or went only a fraction of the time to TBO. Let's not forget the recent judgement against Lyc for the crank problems and all the other problems these "proven designs" have suffered in the last 5-6 years. This is a joke when you are paying $30,00+.

Again, automobile engines running in automobiles is irrelevant to the engineering problems in aviation. There are a handful of Subies flying and more than a couple have already suffered failures of one kind or another. The Lycoming problems you cite are a result of component manufacturing problems, not with the design. The only reason you know about the problems is that the FAA requires stringent reporting requirements so that the history and track record can be examined and reviewed. Where is that documentation on the Subie? It doesn't exist. You don't know of the failures. You don't have any idea if the engineering can hold up in an airplane because there haven't been enough hours flown on them to produce a track record to examine. If the Subie lasts as long as the Lycoming, and it's reliability is even close to the Lycoming, then they will have accomplished something.

BTW, the cost of the Lycoming has more to do with product liability than manufacturing. All it will take is one Subie user (or their family) to sue them and win, and they will be out of business but fast.

 

[rv6ejguy]

Subes

You guys need to get you heads out of the sand. Rotary Airforce has sold over 400 Gyros powered by Sube EJ22 engines over the last ten years. High time one has 2500 hours on it. Fleet has close to 100,000 hours on them. I can't find a single internal mechanical failure in any accident report involving this airframe/ engine combo.

The WW2 aero engines had reduction gears on them to enable higher outputs and more efficient propeller operation. You think you know more than the engineering teams that designed these engines? Using an auto engine which is most efficient turning around 4500 rpm in cruise requires a redrive for the same reasons. This is sound engineering. The redrive also isolate torsionals from the crank and supports prop loads. The good redrives offered by Powersport, Marcotte, NSI and now the damped Eggenfellner solutions have some good to excellent engineering, testing and flight time on them. They are proven and reliable. Certainly some of the redrives offered in the past and even today were/are poor but refinement has got some good ones out there now.

Yes, present state of the art means that the average Sube will be heavier than a Lyc. The E-Subes have higher fuel burn due to their stock ECUs being in open loop at high power settings. With programmable EMSs, we find fuel burn very similar to a Lyc at the same TAS because we can properly map to a more effient AFR. Some new NSI Subes are flying now and we hope these and some Egg owners will be going to Van's this year to test head to head against the Lycs.

Cars on the autobahn are routinely cruised at 4500 rpm + for their whole lives. They are not littering the sides of the road with broken engines.

The crank is smaller on the Sube because it is only a 134 cubic inch engine. All the components are smaller because the must be. This does not mean that they are weaker. Pistons speeds for a Sube at 4500 are similar to a long stroke Lyc at 2400 rpm, therefore inertia loads are similar. They are in no way at any dangerous levels. My Sube knows no difference that it is attached to a redrive spinning a prop than it would being driven on the road at 110 mph.

 

[szicree]

If the Sube is heavier and burns more fuel, why is it better that a Lyc?

 

[f1rocket]

If the Sube is heavier and burns more fuel, why is it better that a Lyc?

Bingo. And I'm the one with my head in the sand!

I'm glad you like your Subie, and I hope it lasts a long time and that you are safe. Although it's not for me, I'm glad it fits for you.

The intent of the thread was not to cast aspersions upon the alternative engine crowd, but rather to give newbies some food for thought when considering engine alternatives. If one were to just consider all the hype out there, an unsuspecting new builder might think that the Subie is a proven, tested, cheaper, more efficient, lighter, easier to operate, easier to install, and effective alternative to Lycoming. While we disagree on whether it is or isn't, folks need to look at all these aspects before deciding which engine is right for them.

 

[Scott DellAngelo]

Cars on the autobahn are routinely cruised at 4500 rpm + for their whole lives. They are not littering the sides of the road with broken engines.

True, but how much horsepower is that engine producing to cruise a car down the road at 4500? I'm betting a bunch less than when pulling the airplane along at 4500 in cruise.

Scott

 

[djvdb63]

Recently an H-6 RV-7 subaru pilot posted speeds and fuel burns from his plane. They were amazingly slow and high, given all the claims.

For example: at 8500 ft

RPM 2200/3970
BURN = 8.6
TAS = 141 (162)
MPG = 18.83

This is about ten knots slower and the same fuel burn as a 160hp lycoming rv7a I know got with no wheel or leg fairings. It will be about 100lbs heavier, and have no provision for a hydrolic prop.

With all the superiority, it makes you wonder where the performance is...

In fairness, it should be noted that that same pilot, posting two days ago on the Egg list, says he is now getting about 10 knots more than last August (when those numbers you quoted were first posted), after adding upper and lower intersection fairings. He also indicates there is considerably more that can be done regarding drag reduction vis-a-vis the cowl installation of Egg's H-6 engine.

Let me make a few random Egg-Sub observations...not as a customer, but as an observer and potential customer:

My take, as a long-time observer, on the Egg-Sub situation is that, with the H-6, they have finally achieved performance roughly equal to a 160 hp O-320 or IO-320, but at a considerable weight penalty (the two H-6 RV-7A's that have produced the most data thus far are both coming in with empty weights of about 1280 lbs...both fairly well equipped). This is disregarding the issues of initial engine cost & initial prop cost. It is also disregarding issues of resale value, durability, overhaul cost, etc....much of which remains unknown.

One can only speculate as to why the H-6 doesn't produce performance more in keeping with it's claimed 190 hp. Other than it's weight, I would suspect cooling drag as the culprit...which has been extensively debated on the Egg Yahoo list. And the required 3-blade prop might cost 2 or 3 kt., and the PSRU might cost some power as well. Mr. Egg consistently refuses to produced dyno data to support his HP claims, but I would guess that a dyno would likely confirm his HP estimates since he is not altering the basic engine in any substantial way from it's automobile configuration.

The supercharged 2.5L STi Egg engine is a different story. Production is currently "on hold" while initial installation and teething difficuties are sorted out. My guess is that this engine, once optimized, will produce performance somewhere between an 180 hp and 200 hp Lycoming with somewhat less of a weight penalty. The complexity of this engine installation, with resultant higher maintenance and pilot work-load issues...as well as durability issues, will lilkely be the trade-off here.

My biggest concern about Egg's engine packages remains the high-flow fuel system with both fuel pumps on the floor of the cockpit. Just a visceral safety concern that I have in the event of a mishap. Apparently the high flow is necessitated by the FI system on the Sub. A more desirable solution....low flow system from wings to header tank...high flow from header tank to engine...is apparently not possible on RV's but has been used on Glastars.

Another concern is that Egg has become much less transparent in the past couple of years. His list is now heavily edited, and almost nothing negative is allowed to get through. This makes it harder to really assess the degree of customer satisfaction and feedback. But I somewhat understand his defensiveness, having watched him get ripped and flamed mercilously from various quarters in the past.

Remember the percieved benefits: MUCH lower vibration than a 4-cyl Lycoming. Effective cabin heat for us northerners. Lower pilot workload...like a car. Just start it up and go....full throttle from takeoff until descent...using the prop controller to regulate power. No mixture to worry about. No carb heat. Very simple initial installation. Projected lower ongoing maintenance workload and costs.

Overall I think Jan deserves credit as there are arond 100 of his engines flying. Nobody has gotten ripped off. Most of his customers are happy (I think...as this is getting harder to assess). His movement is growing...and his product is improving.

Of course, time will tell, as it always does.

Dan

 

[rv8ch]

Old vs. the new

The debate about traditional aviation engines vs. the auto conversions reminds me of the command line interface vs. graphical user interface debates of the middle 80s when I worked for IBM. I did a blasphemous thing and bought an Apple Macintosh in 1984, which of course had a GUI. While I still enjoy using a CLI on my linux machines, most of my work is with the GUI.

Still being a blasphemous kind of guy 20 years later, I bought an Eggenfellner Subaru 2.5XT with a supercharger. I enjoy flying behind any kind of engine, but I only have aircraft available to me with traditional aviation engines, which is why I chose the subaru for this project. If I like it, I'll keep it. If not, I'll yank it out and install something else. Hopefully before the end of the year I'll be flying, and I'll be happy to report any details.

 

[rv6ejguy]

True, but how much horsepower is that engine producing to cruise a car down the road at 4500? I'm betting a bunch less than when pulling the airplane along at 4500 in cruise.

Scott

If we take average hp to take a modern car down the road at 70mph being around 20 hp, to cruise at 140 mph on the autobahn would take around 160 hp. Certainly in the ballpark of a Lyc O-360 at 75%. My BMW turns about 3000 rpm at 75 mph in top gear so 5600 to do 140 mph. This happens every day in Europe. Even the 1300-1600cc cars are cruised at 100+mph for hours on end, foot to the floor WOT 6000+ rpm, just like hundreds of showroom stock endurance racing cars.

I'm just wondering what evidence you fellows have to prove that auto engines are having internal mechanical failures in aircraft because they can't take it? Please show us.

DJVDB63 sums things up very well here with the Egg conversions from a neutral standpoint. The supercharged or turbocharged 4 cylinder Subes and Wankels would appear to offer close to equal weight and performance to the Lyc with all the advantages he listes here. Hundreds of people are buying and flying these conversions. It's unlikely that none of them considered a Lycoming and ended up spending $20,000+ on a Sube or Wankel instead by mistake. Most users to date seem quite pleased with their choices and few problems have been reported. These engines have accumulated several thousand flight hours to date. Choosing a Sube or Wankel is not a death wish, it's just another choice we have now instead of a Lyc. Eggenfellner and others are advancing the installation and performance of the Sube and deserve much credit. I develop my turboed Sube to make it better. Others such as Tracy Crook and PowerSport with the Wankels have forged the way for others to follow with those engines.

 

[Jconard]

Since the begining of aviation people have tried to convert auto engines. So far the only successful ones have been the air cooled VW, and the old jennies.

The performance per weight is not equal...look at the numbers.

The advantages are mostly percieved. People believe that electronic injection, etc are superior. For an engine with a wide rage of rpm operation, and a need for smooth but instant throttle response that modern injection does have advantages. Neither are necessary in an aircraft. The magneto, and constant rate fuel injection or carb are simple, elegant, and bulletproof.

The hundreds of flying examples argument is simply laughable. There are more lycoming hours flown today, than all the subaru hours combined.

As for ability to withstand the forces, I have rebuilt both types of engines, and have seen the bearing and crank setups. The auto is a great design for rapid reving, crisp throttle response, and an engine which will spend most of its life far below maximum output.

The aircraft crank is beefy to handle resonance and gyroscopic loads from the prop. Remembber that a prop is a 60 lb pair of flywheel arms that are constantly accelerating and decelerating. This adds torsional stress and harmonics that an auto crank is not able to handle. This is why the VW conversions, even with chromoly scat cranks, (far stronger than a sube crank, often used in alcohol midgets), still can only use a lightweight wooden prop.

Air cooling is also superior. The goal is to transfer heat with minimal air, hence minimal drag. Each instance of heat transfer is less than 100% efficient. So, transferring metal to water (engine) and then water to air(radiator) has double the opportunity for thermal inneficiency, not to mention the drag of the pumps.

As for the idea that hundreds of people cannot be wrong...note that not one single solitary aircraft mfg uses a car conversion. So I guess those thousands of engineers, not to mention managers, who face real consequences and liability for their choices are wrong.

I guess I chalk it up to "unthinking modernism". I read people referring to the "lycosaur", and extolling the benefits of modern fuel management. However, all of those advances are for operating requirements which are simply not present in a prop plane. Which is why the egg burns as much and typically a little more fuel, per speed, than does the lowly lycosaur. It is also why, even given all the best aeronautical engineers, designers, and tons of testing, a Fadec only improves the economy of a lycoming by 15% at most.

As for simple operation....the same people who joyfully get rid of a mixture knob are equipping their planes with multiple EFIS and Autopilots....the accident reports will show that mixture knobs are not that complex, but avionics are. Do we really have pilots who cannot operate their engine? Should those pilots be allowed to operate the infinitely more complex flip flop radio?

A competant pilot with an old lycosaur, can cruise all day at 175 knots and less than 10 gph (Dan Checkoway). No subaru to date can come close. While the lycosaur is cruising faster, on less fuel, and much less weight, it probably also has half the internal engine and external accessory parts. Probability of failure is the square of complexity...so......why would you spend the money to go slower, on more fuel, with more weight, and extraordinarily higher risk of failure? To eliminate a mixture knob? Or simply to prove how much smarter you are than all those old lycosaur engineers?

 

[ship]

Extremely Long Post

Nice debate,

Nice write up/summary from Ship,

Question for "Ship":
Ship, could you shed more light on your statement?

IMHO: Everyone should read JConard's post above... he has it right

I've worked closely with DeltaHawk since OSH '02. Details below if anyone's inclined to read through all this drivel.

(This is not a pitch "for" DH or "against" anything else....as you'll see below)

Side note: My opinions re DH being "the only diesel with commercial potential" were formed PRIOR to my getting involved with the company....i.e. that's what LED me to get involved with them in the first place.

Being involved with DH has afforded me the opportunity to examine every "aviation" engine that exists and hear about every engine that doesn't.

Myth: $20k for an "ancient-design" Lyco/clone engine is a rip-off
Fact: there's FAR less profit in a clone than you might think.

I've been an "engine guy" since before I could walk. Engineer by training (hated it). Business guy by profession. Raced a lot. Busted/fried more engines than I can count.

When I started building my RV8, I was naturally VERY interested in every engine on the market or those in the pipeline. Especially the auto conversions.

I read/heard all the stories about Lycosaurs, stone-age, etc. Also QUICKLY found/heard all of the "modern" engine offerings. Some made sense, some were total crap.

Looked at rotaries, turbines, subies, chevy's, radials, etc.....everything
I looked deeeep into the "RV turbines" as a potential investor. 'Nuff said.

The Superior/ECI clones became my favorite traditional engines.
The Egg-Subie became my favorite choice of all non-aviaiton engines.
DeltaHawk became my choice for "new" aviation engines.

The DeltaHawk attracted me for one reason: they had the design that was closest to the pure aviation mission. I also immediately liked the execution, i.e. strict discipline to the KISS philosophy within the design compromises that MUST be made for EVERY engine/mission combination.

I offered my help on the business side along with my engine "knowledge" and another set of engineering eyeballs.

Even so, the DH is very much an experimental engine for now. FAA certification is only part of the story. Proper FWF development at the OEM level is a LOT of work. Fleet hours need to be accumulated, etc.

Bored yet? Read on.

Like most specialized industries, the engine "world" is small. Take it a step further: the aviation engine "world" is microscopic.

To put it mildly, everyone in the "airplane engine" biz knows everyone else.

Everyone closely guards their "stuff" but we all talk to each other at the shows and keep close tabs on what's happening. We all eyeball each other's engines VERY closely and ask highly detailed questions, most of which are answered quite openly.

Bottom line: it's pretty hard to fool anyone for very long in the engine world. The "real" are quickly separated from the "not real". Suffice to say I will not trash anyone publicly regardless of my well-founded opinions.

Lest anyone get the wrong idea: It doesn't mean the engine folks all "like" each other. But there is a healthy respect among most of the various competitors (but not all ).

How does all this all relate to "traditional vs. alternative"?

If you think THESE debates are "endless" on these forums, you should hear it among the engine vendors!!!

The ORIGINAL premise of this thread is EXACTLY on the money: do you want to "fly"? or do you want to "try"? There is no "right" answer to this question.

Like most engine debates in experimental aviation, this one has veered into muddy waters by mixing unrelated elements.

Too often these "engine debates" fail to separate "quality" from "design".

The other problem is separating "garage" knowledge from true expertise.

KEEP THIS IN MIND: If you chose an RV, you are NOT an "experimental" builder ... you are a KIT builder of a VERY CONVENTIONAL aircraft with conservative design elements.

10,000 people chose RV's because they represent the best combination of compromises in the history of aviation. Same with Cessna. It's no coincidence. They got it right.

Same goes for engines. There's a REASON that Lycoming is the dominant engine in GA. They got it right (design).

This discussion boils down to "aircraft vs. non-aircraft" engines.

Underneath all the debate, the MOST important element in ALL engine design is "suitability", i.e. what is the BEST combination of COMPROMISES for a given application taking into account all of the requirements.

The mission ...and this alone...leads to the final design choices of any engine (or airplane for that matter).

As others on this thread including me have stated, Engines are Engines. There really is NOTHING new. It's only the APPLICATION that's "new".

Translation: there is a REASON that what works is what works, i.e. it's ALL been done before. There are BETTER ways to MAKE engines, and better CONTROLS, better MATERIALS, etc. but matching the DESIGN to the MISSION is the single best predictor of long-term success.

Did anyone notice that Honda's engine looks suspiciously like a "modernized" Lycoming/TCM? The core "design" is exactly the same with more sophisticated peripherals.....just like our modern car engines are still identical "designs" to those from 75 years ago.

I can GUARANTEE that Honda would probably design the same thing from scratch if they never saw an airplane before.

I know people don't want to hear this but here goes: It's VERY easy to make the case that a "crappy" Lycoming is a better AIRCRAFT engine than a state-of-the-art japanese/german/etc. car engine.

BMW started out life making airplane engines. The BMW 6cyl is the smoothest piston engine in existence by far. Bulletproof. Would I put one in my plane? No.

Does that mean a Subie is a bad choice? NO!! It simply means that it may not be as reliable/durable/efficient in an aircraft as it was in a car. It wasn't designed for aircraft, it was designed for cars. There's no free lunch.

The Subie is probably the closest to an aircraft engine that a car engine can be.

Like taildragger vs. nosedragger, it all boils down to your particular mission priorities and comfort level.

Do your homework. Make your choice. Go for it.

I could go on for hours.....but I'll spare everyone any further pain.

In the next installment , we'll talk about the concepts that are most important to aviation engine design and why they are VERY different in car engines.
-- specific output
-- duty cycle
-- mission-matching
-- the "complexity matrix"
-- the "durability paradox" (no, it's not the Probability Engine)

FUN FACTS:
marine diesels
-- world's largest engine 3,000 tons
-- world's most powerful engine 100,000 hp
-- world's most efficient engine .27 BSFC
-- world's largest crankshaft 100 tons
-- world's biggest piston 10 feet long
-- world's slowest engine 50 RPM
-- world's biggest oil change 1500 gallons
it's all the same engine!!

 

[RudiGreyling]

Thanks Guys,

As a newbie I like the debate, I am learning a hellaofalot lot in a short space...keep it going, and keep it clean, no low blows!

Regards
Rudi

 

[rv6ejguy]

MFGs

Well the statement above that no manufacturers use auto engines is not true. As I said before, you people not directly involved in auto engine conversions assume a lot but sometimes don't know. Rotary Airforce up here in Canada has sold over 400 RAF 2000 gyrocopters over the last 10+ years. Every one is powered by a Subaru engine. High time airframe has 2500 hours on it, fleet has around 100,000 flight hours. I have not found any internal engine failures as accident causes on these.

Of course Sube engines have not accumulated the millions of flight hours that Lycs have because only a few hundred are flying and mainly in the last 5 years. The only sane thing to say is wait and see. Saying these engines are unsuitable for aircraft use is based on feelings and emotions, not facts. Show me some facts that Subes are breaking cranks or rods. We know that Lycs have their problems even after 40+ years of trying to get it right. Look at the Ads still being issued on them and the lawsuits. Problems with supporting systems cause most auto conversion failures on Subes, not the core engine. The same thing applies to Lys and carb icing. Design a good system, use it correctly and you won't have too many problems.

The Lyc has proven to be an acceptable engine to power light aircraft however they are not cheap, they do break sometimes they do shake etc. The Sube and Wankel have also been proven to do the job but when small private companies have to foot the bill for engineering a total firewall forward package so that the masses get a reliable powerplant system in small quantities, things take time to test and longer to prove. Give credit to people like Eggenfellner who test and develop these engines to give others an alternative to the Lyc if they want it. Don't slam everyone who tries something different. Experimental aviation is just that. If nothing new is ever tried, we'll always be flying the same old stuff. We have to start this development somewhere and improve as we learn.

As for all you guys breaking race engines. You must have the wrong builders or be overrevving them. I have built over 200 performance and race engines, mostly turbocharged road racing 4 and 6 cylinders. None have ever broken a rod or crankshaft even producing over 200hp/ liter at 8500 rpm. You just gotta know what you are doing and choose the right engine to start with.

We used to here the same thing from the large displacement- slow turning guys- "you high revving turbo guys will never finish the race" within 1 year we were on pole, 2 races later we won. That next year we won the championship with 6 more to follow. Then they wanted to ban us because it was unfair! Same thing happened in F1 and IMSA. There are teething problems to solve but with hard work, it can be done.

My RV6A weighs 1140 lbs. empty and will true 182 knots with a Sube at altitude. Not too bad considering the that the prop cannot absorb anything close to full power above 10,000 feet. With further R&D, no doubt weight, speed and fuel burn can be improved. Recent leaning experiments have got the SFC into the .42 range which is equal to the Lyc. New radiators may allow a reduction of 15-20 lbs. from the airframe and a further reduction in drag. This is my first attempt. Our new RV10 will be powered by a twin turbo Subaru EG33 applying all the lessons learned on the -6A and te EJ22T.

 

[Jconard]

First,

I hate to call you out, but no major, open wheel road racing series I can think of has allowed turbocharging for years, unless you mean to say you built engines for F1 or CART....is your name cosworth?

Second those 8500rpm (slow) and even 12,500 rpm engnes (formula atlantic or supervee) will break if not freshened after EVERY race weekend....same with the racing subes, at least at high specific outputs. As for engine builders...these guys know what they are doing, the annual budget for a club racer in F2000 is more than half a million and double that for a formula Atlantic or Super Vee effort. You cannot spin an engine at high specific output evels all day, and at high rp, without constant maintenance. Lasting 2000 hours? forget it, those engines don't see 100 hours in two seasons of racing, but they will be rebuilt 20-30 times in that period.

Third, a gyrocopter is not an airplane and does not have the same stresses.

Fourth, nothing I have said is emotion. I road raced for 13 years. I am simply pointing out that the things we needed for that mission are innapplicable, and unnecesary for driving an airplane.

Fifth, the beauty of slow turning, in an airplane is that while inertial force is directly proportional to mass, it is exponentially applicaple to speed/acceleration. In other words, the stresses are high.

182kts at altitude? nice job with a complex turbocharged conversion, but still slower than an angle valve 360 normally aspirated.

The best part of a car engine in a race car is that when it blows, you simply pull over. You do not crash into someones house. A high wing loaded, constant speed prop sport plane, with an engine failure, is coming down NOW, and fast.

Again, why is it that in 100 years, with the plentiful supply of auto engines, and countless dollars spent, the lasting, light, and good performing packages are still normally aspirates, air cooled, slow turning, direct drive engines?

 

[hecilopter]

How I made my choice and a future alternative...

I too have been through the decision making process of what to power my RV-7A with. I convinced myself both ways at least 3 times (Superior or subie). Money had a lot to do with my decision, time another. In the end the subie
1) didn't cost any less,
2) had much longer wait time to get and
3) even though there are lots of people using it, I still have yet to see the overwhelming majority of people rushing to use it. Meanwhile I wanted to get finished and fly.

My choice, I wound up going with Superior (any other lyc alternative would be just as good). They HAVE made some improvements to lyc's old design and the Hartzell propellor I chose to go with it was TESTED to be a match with the pulse power strokes and approved (with mags). And in the end it was cheaper. I went with the 8.5:1 pistons to have the OPTION of using MoGas if I ever need to. That way I won't be left out in the cold at the end of 100LL(?) (I personally believe 100LL will probably go away someday, but they will probably come out with a replacement (unleaded) fuel we can still use.)

My 2 cents on a "perfect" aircraft engine:

While not available now, fuel cells and battery technology will improve in the coming years (esp. with fuel prices escalating). An ELECTRIC aircraft engine would be perfect. It would have few moving parts, be turbine smooth, VERY quiet, and would have the same power output at ANY altitude. Backup batteries could add to reliability. Wouldn't want to fly it near a thunderstorm however, a lightning strike would ruin your day

 

[rv6ejguy]

Again, you assume. I did not say that I raced open wheel cars or built engines for them. I built and raced closed wheel cars. Then engines had to last for the whole season. I never said a race engine was going to last 2000 hours. The maintenance between races was to check valve lash, compression, leakdown and make sure all the exhaust system bolts were tight. The same Mobil 1 oil was used for the whole season. One Toyota engine went 4 race seasons on the same set of bearings, same pistons, same rods, block, crank, head, valve job, turbo. Just rings and gaskets for 62 races. 47 class wins. 360 hp at 7750rpm out of a 1.7L 2 valve pushrod engine.

I am not advocating building a fire breathing 2.5L STI based motor to jam out 400hp at 8000 rpm for RVs. I could do it, but you are right, it would probably last 100-200 hours and run the tanks dry in an hour. Not very practical. We run most of the Subes at 4400-4800 rpm. With the turbo, we never run ours over 4600 which keeps inertial stresses lower than an atmo version. We only run 38 inches for takeoff and 35 for climb, 30 for cruise. This does not stress the EJ22T as it was engineered to do this from Fuji.

The stresses are HIGHER on a Lyc at 2700 rpm if you work the math and use the reciprocating weights of the components and the piston speeds. The EJ22 stroke is only 75mm. Piston speeds largely determine the rev capability and stresses on engines. F1 engines turning 18,000 rpm have many small pistons and extremely short strokes. 4600 rpm for the Sube is no harder than 2700 on the Lyc. It just sounds scary if you think in Lyc. terms. Rotax's turn 5500-6000. So what, they work because they were designed that way. The EJ22 is designed to run at a maximum of 6250 rpm. Factory redlines are set conservatively to ensure that if someone in Germany wants to cruise flat out from Munich to Stuttgart, they can. If the engine was fundamentally incapable of running at such rpms continuously, wouldn't those 3 Legacy's that set the 100,000 km speed record running at 6000-6500 rpm for 400 straight hours all have grenaded? Again, I say show me some facts that Subes blow up running at 4600 rpm in aircraft.

Even Van's is eyeing developments like the Egg Subes and the Powersport Wankels with interest. They have openly invited anyone to come down to Aurora to fly against their Lycs. Powersport has, some Egg boys are about to and some NSI guys have also expressed interest. Van's is not saying that auto conversion can't do it. They just say we reserve judgement until we see it with our own eyes. Even then, they are likely to recommend Lycs as a first choice until the FWF companies have 10s of thousands of hours built up.





A gyro turns a prop through a redrive just like in an RV. I'm sorry if you don't see the similarity here???

182 knots and we only have 134 cubic inches and we are just getting started with a prop not even close to optimal. I don't think that's too bad.

 

[szicree]

Seems unfair to mention the number of AD's on Lycs since auto engines have no such requirement. Actually, the fact that there is no system in place for disseminating such info is another reason to be cautious about auto conversions. Is Sube going to inform us if they discover a metalurgic issue with cranks produced many years ago? They most certainly will not because of the legal exposure.

I admire the ingenuity of those who've adapted these motors to planes, but I think the key word here is ADAPT. Why mate a hi revving engine to a system that likes to turn slowly? Can somebody tell me WHY??

Also, I notice that the Rotary Airforce website says their Subes have 1000 hour TBO, while Eggenfellner says 2000. I'm sure the Egg setup is a triumph of fabrication, but their FAQ page seems to rely heavily on answers of the form "we've never seen a failure, so it must be strong" to answer questions about reliability. I'm kind of a science type of guy and would like to see some more controlled test data instead of user testimonials.

 

[gmcjetpilot]

What happened? New Rotary data.

Most info is covered on the first 3 pages of this thread. There is no need to re-state the obvious or need to defend auto-engines or Lycoming. The numbers speak for themselves. To touch on a few points:

Talk is nice but here are some hard numbers. Van's aircraft compared two RV-8's, both with Rotary engines from power sport and 3 blade MT props.
http://www.powersportaviation.com/
They are based on a highly modified Mazda B13, which is an outgrowth of the late Everett Hatch's work. They are beautifully designed and produced. These two RV-8's were flown side by side with two other factory planes,RV-8's, one 180hp RV-8 (Dilbert) with a new blended Hartzell and the other IO-360 200hp RV-8a (Tweety) with standard Hartzell. The findings were the rotary burned more fuel and was louder and heaver than either Lycoming powered RV-8. No big surprise. The rotary did well with time to climb and top speed at 8000 feet. Top speed of the faster of the two rotory RV-8's was 3 MPH faster than the 180hp Lyc Dilbert. Time to climb was 15 seconds faster than Dilbert. The rotary burned 7.1 gal vs. 4.6 for Dilbert. Next, was a close course takeoff-climb-cruise-approach and land; the rotary burned 12.9 gal vs. 8.9 gal for Dilbert. (Note: Dilbert has a pre-production FADEC and Tweety had a tired IO-360 (200HP). Dilbert 180hp (RV-8) was faster than Tweety 200hp (RV-8A), part in due to the tri-gear, older prop and the high time 200hp engine down on power. I called and asked Ken in Van's engineering dept. I must admit the rotary is putting out at least 180hp and matching the performace of the Lyc but with some cons: cost, weight, fuel burn, noise and longer build time. I think that is still pretty good because most auto conversons have all the cons but also have lower performance. It is one thing to say my engine makes 200 hp and another to get that to the prop. (like the Subie: Higher cost, higher weight and longer build time for less performace; Pros: Subjective smoothness and less noise). At least the rotary is up to snuff in power. Remember this is a highly modified custom rotary and is only partially based on a Mazda B13. A Mazda you convert will not perform as well, may be closer to a 160hp RV, however you can still expect the fuel burn and noise issue. The plus of the do it yourself is lower cost, but at the trade time and sweat. Performance likely will not be as good as a powersport engine, but they (powersport) are out of engine production at present. I know Tracy Cook is now developing the new three rotor Mazda engine under build for many years. We shall see. Tracy Cook is a straight shooter and realistic. Don't get me wrong I love experimentation, but that is the point. If you want to fly get a Lycoming. If you want to be differnt, experiment and tinker than an auto engine might be for you.

Bottom Line, Tracy Cook and builders using rotary engines are doing a great job, but rotary engines will always be louder, more thirsty and have more "systems": radiator, pumps and electrically dependant fuel pump/ignition/fuel injector (engine computer), which reduces reliability at least from a statistical standpoint. Mechanical fuel pumps, mechanical fuel injection, carb and magnetos or self-powered electronic ignitions are going to be more redundant and reliabile. This is where people might confuse "Farm tractor" technology witha Lycoming, but it works and simplifies the installation.

Subaru: Great cars and as far as an aircraft engine, so so. It is just a horizontally opposed four-stroke internal combustion water cooled gas engine with overhead cams. No earth shaking technology. It is small displacment with tiny pistons so it is a higher reving engine. Again not big deal, we know turning an engine faster makes more power. The bad part is you need a reduction drive becaue props don't like to be turned too fast or they go supersonic at the tips and loose efficency. The cubic inches are half of what a Lycoming is. The Subie will be working hard to keep up. Let the numbers speak for themselves again. Subie RVs weight at least 100lbs or more than a Lycoming powered RV, and the Subie has the performance of a 150/160hp RV at best. You are stuck with very expensive electric props because a fixed pitch would really limit the performance even more. Hydraulic prop is not an option and fixed pitch would reduce the RPM dependant power plant. Also the reduction drive adds more complexity, even if they claim 100% reliable, there is nothing 100% that is mechanical. Also you will spend way more to get an Egg-in-Kit than an O-320. Buy an O-320 and use the stock off the shelf Vans kit parts and install with off the shelf installation components and be done with it. The airplane is designed for a Lycoming after all. Much simpler systems and higher resale. Why resale? Reason, any mechanic at any airport can work on a Lycoming and has parts and tools. That does not apply to a Subie. Most people buying a second hand RV will likely need to farm out some of the maintenance and 100% of the condition inspection to an A&P (mechanic). An A&P may not want to deal with an auto engine they are not familiar with. Again LET THE NUMBERS SPEAK, higher weight, cost and lower performance than a Lycoming. The only Subie that I saw match a Lycoming was a custom well designed turbo charge Subie and that did not start becoming an advantage until above 11,000 feet, and then by only 1 mph or two. To use a turbo you better get an O2 mask. PS, A Lycoming can be turbo charged also and I expect the Lycoming would still out perform the turbo Subie. Why? becaue the Lycoming and its turbo are designed for aircraft use, not car use.

Last the Lycoming and clones are not hammered out by a black smith on an anvil. They don't shake like crazy. A well ballanced prop and all 4 cylinders producing even power will produce a very smooth ride. Turbine smooth? No. With all due respect to those who extol the virtue of auto engines don?t know what goes into an air-cooled horizontally opposed engine. They are purpose built to directly drive an aircraft propeller at low RPM, high torque, low weight with integral prop hydraulics and accessory and fuel pump drives. If you were to design an air-cooled aircraft engine today, that would fit into to today?s aircraft cowls it would look like a Lycoming. 4 stroke technology is not new and innovations for cars has to do more with fuel economy from the electronics than the internals, or at least internals of a low RPM, high torque engine. Auto engines operate in a wide range of powers from idle to full power and typically operate at a low (%) power on a continuous basis. Asking them to do 100% for extended periods is asking for a lot. Overhead cams and multi valves and are not necessary in an engine turning a constant RPM with a max of 2,700 RPM. Of course the approx max prop RPM is around 2,700 rpm, which is no accident. Again aircraft engine engineered for aircraft and direct drive of a prop. Spinning your engine faster and making more power on smaller displacment is not new. There are many geared aircraft engines.

An aircraft air-cooled engine uses very high tech materials and modern machine processes. Some tolerances are extremely tight and the appearance of a cast case should not make you think it is crude. In fact the case halves have flatness and positional tolerances as tight as found anywhere in any engine. If you want modern fuel injection and electronic ignition or turbo charger or even FADEC you can add it. As far as reliability of a Lycoming and tracking of engine problems that speaks for it self, 60 years of service and millions of flight hours. WWII and pre & post war research (NACA/NASA) developed technology that is incorporated in our little aircraft engines. Also new inovations as cam oilers and roller cam followers are now being introduced to Lycoming. With the mass total number in the field over 60 years, failure rate is very low. Catastrophic failures are rare. The ones that do occur are offten from poor maintenace or abuse factors. Failures from no where are even more rare, not withstanding the batch of bad cranks a few years ago. However auto guys need to prove something and point to a RV accident in Oregon a few years ago with a modified rebuilt Lycoming. I have nothing to prove but before you plunk down almost $40 grand for a Subie kit and electric propeller look at a new Lycoming and a Sench fixed metal prop, engine $19K, Prop $2.5K and installation kit $2K= less than $25K. Now price a Subie kit. Don't forget you will need a prop that cost almost 10 grand. Also with all the extra plumbing in the aircraft you will spend more time with the installation. Also check what a Subie powered RV sells for. How many auto conversions have failed due to engine failure? Don?t know. The tracking is somewhat hit and miss, but the ones I have read about were caused by their more complex support systems, belts or total reliance on electrical power. With so few flying over a short period it remains yet to be determined how the reduction drives, bearings, crank, rods, pistons and valves will do in service. These engines are running at +6000 RPM in planes. My old Subie would turn 2,500 RPM max on the freeway.

Just don't get hyped the the Lycoming is crude or inferior. Weight is a big deal in a little plane. 100 lbs to the gross weight is unacceptable. At least the rotary is only 30-70 lbs more and matches the 180HP Lyc, which is very good. You still have the expensice prop to buy. Again, if you want to fly, go with the engine the RV was designed around , the Lycoming. If you want to be differnt and experiment than the auto engine may be great for you, but know what you are getting involved in. Also check to see if you can get it insured with an auo engine if that is your plan down the road.

Cheers George

 

[rv6ejguy]

Nobody here on the auto side is saying that the Lyc is a piece of junk. Nobody here is saying that the comercially available auto conversions are cheaper than the Lycs and their clones. Nobody is saying that they outperform a Lyc in speed or fuel burn. I state all of this near the end of my recent article in Kitplanes where I tried to be as subjective as possible in the comparison. If you want the highest payload, good speed, good fuel burn and lowest cost, a Lyc clone is the best choice, no point debating that.

The big thing you are missing is that not everyone has the same priorities for an engine. Smoothness and no fuss are big on the list for many who have chosen the Sube or Wankels. Lower fuel burn at reduced power settings seem to be important for others with the Eggs. But I think the biggest thing is that not everyone wants a 5L Mustang which is what a Lyc powered RV is. It does the job well, is well proven but everyone has one. I like something technically different and I suspect many other Sube and Wankel guys also do. If you like Lycs, by all means fly them and enjoy them. When I land somewhere, everyone wants to know all about the turbo Sube under the cowling and comment on how nice it sounds. They couldn't care less about the other two Lyc RVs parked next to me because they've seen it all before.

The initial costs may be high for a conversion but the overhaul costs are MUCH lower than a Lyc. Figure $500-750 for the DIY and maybe $1500-$2500 if a Sube or Wankel is redone professionally. Even if the TBO is only 1000 hrs., this looks good for people who fly a lot. My hangar mate just dropped $6000 to buy 4 new jugs, 4 exhaust valves, pistons and rings, gaskets etc. for his O-360 with just 1300 hrs. TT. (Low compression, high oil consumption on 2 holes and broken rings found). This engine was flown carefully with proper maintenace for its whole life. There are advantages and disadvantages to both engine types.

Statements like the Subes running at 6000 rpm are just not true. Egg runs a max of around 4900, I run 4600 on mine. This is JUST like a Lyc running 2700 as far as stresses and wear go. Just because you drive at 2500 rpm has NOTHING to do with the fact that these engines happily run at 4600 rpm for very long periods. This IS proven and since nobody here has stepped up to the plate with evidence to the contrary, maybe it's time to quit harping on it.

In fact, any good, modern engine is capable of this. One of my friends raced a stock 4AGE powered MR2 in edurance racing series all over North America. The engine had 25,000 miles on it when he bought the car and he put 45,000 RACE miles on it over the next 6 years. WOT, shifting at the stock redline of 7500 rpm. It was never touched in that time.

Wankel and Sube conversions are in their infancy and there is still much to be learned with redrives, cooling and weight reduction along with ECU tuning, props and blown aspiration. We in this field are working to improve these factors plus hp and fuel burn and we are making these aspects better. You will see improvements in the coming years. Tracy Crook and Ed Anderson are finding better fuel specifics with extensive leaning- something the Wankel seems to take well to.

Lack of a good, inexpensive variable pitch prop is a major issue with auto conversions. Can't blame that on the engines. Some developments here are in the pipeline. NSI claims some great performance from their CAP equipped Subes but we'll have to wait and see how they compare against Van's demonstrators.

Supporting systems such as fuel, ignition, radiators, alternators and dual batteries receive a lot of attention with auto conversions and rightly so as these cause the majority of "failures". Several groups post flight proven designs for others to follow to avoid possible problems.

The atmo Wankels do have the high noise level problem to contend with and much muffler development has taken place. The latest idea is simply to mildly turbocharge them. This makes them very quiet, improves power to weight ratio and altitude performance and reduces rpms required across the board. Some like John Slade in his Cozy are doing much good testing here. I am of the same opionion with the Subes- turbo is the way to go with higher CRs to get better fuel specifics and keeping the noise low. Working well so far, just need a better prop to make it all come together.

 

[szicree]

But I think the biggest thing is that not everyone wants a 5L Mustang which is what a Lyc powered RV is. It does the job well, is well proven but everyone has one. I like something technically different and I suspect many other Sube and Wankel guys also do. If you like Lycs, by all means fly them and enjoy them. When I land somewhere, everyone wants to know all about the turbo Sube under the cowling and comment on how nice it sounds. They couldn't care less about the other two Lyc RVs parked next to me because they've seen it all before.

I think you've hit the nail on the head here. It's the same as using a Nailhead instead of a chev 350 in a hotrod -- just something different and interesting. We all love to see these individualists do their thing. Keep it up rv6eguy. As for me, I'm sticking a IO360 in my Tacoma : )

 

[gmcjetpilot]

love Lycoming, appreciate the auto engines

Dear rv6ejguy: I agree with you but detect a little defensiveness. No need, you make real good points and agree with you 100%. Obviously I have a Lycoming, but I have been in experimental aircraft for 15 years, and following alternate engine developments the whole time.

"Nobody here on the auto side is saying that the Lyc is a piece of junk. Nobody.........."
Yea some do, especially when selling something, that is the first thing that gets mentioned, but I don't really care because the performance and history speaks for itself. Folks like Tracy Crook (rotary) are real straight shooters, and others that were making some claims have backed down. Could a Lycoming be better? Yes, after the 1950's piston aircraft engine development slowed with the Jet age, but now there is a new wave of developments in better fuel injection, induction, ignition (electronic), FADEC and roller cams. All this is thanks to the experimental aircraft market. Plus we have 3 manufactures for parts now. Subie has just one. Is an air-cooled Lycoming more sensitive to poor operating practice than a water-cooled engine? yes, but it's not a difficult thing to operate within the limits for long life (like CHT400F max, oil Temp 190-210F), lean properly and operate frequently. Sitting and corrosion is a big killer. Like anything there are trade offs and limitations. With Lycoming, it is CHT, frequent oil changes (25-50 hours) and long periods of dis-use.

"The big thing you are missing is that not everyone has the same priorities for an engine. Smoothness and no fuss are big........."
I agree, but a Lycoming is not rough, and preventive maintenance, oil changes and plugs, is all my Lyc engines have required, past and present. Yes they shake, but some people put on 3 blade composite / wood prop on their Lyc and swear they have died and gone to heaven. Still, with big piston power pulses? hanging off 4 little rubber mounts and a prop spinning on the very end, something is going to moving. Also as far as fuel efficency, the Subie is not better. There is no substitute for physics. All gas engines operate within a limited range of efficency. There is no free lunch. One way to way to improve efficency is increase compression. In a Lycoming with a coffee-can size piston you need to be careful with high compression, but it can be done with care. Super charges or turbo charges is the other option. Diesels are more efficient simply because they operate at very high compression ratios, but they are heaver engines (or should be) to take all that pounding. Deltahawk Diesels? Smooth? Fuel savings? Installed weight? Cost??? We shall see. Numbers speak.


"The initial costs may be high for a conversion but the overhaul costs are MUCH lower than a Lyc. Figure $500-750 for the DIY and maybe $1500-$2500 if a Subie or Wankel is redone professionally..."
Agree, overhaul cost is less, but will that offset the initial cost and expensive prop? A Pro Lycoming overhaul is around $10-$12 grand. With the wide availability of parts from ECI, Superior and Lycoming, part prices are not bad. You can buy a whole new cylinder assembly, piston, valves etc for a grand. If you do-it-yourself you can overhaul a Lyc, parts, machining w/ accessory overhaul farmed out for less than 8 grand or $4 bucks an hour, or the price of one gal of gas(almost). Also, you can buy a new Lycoming, fixed prop and all accessories for $18,000, new everything. Installed w/ prop for as little as $23 grand, giving you 10-20 years of flying before it's first overhaul. If you are a good bargin hunter you can save a lot of money buying some used components, but you have to look. The rotary guys have the best do-it-yourself program with builder support, books and critical parts availability (Tracy Crook). I think the price is around $12 grand with a fixed pitch prop and a lot of work for a home grown Mazda engine.

"Statements like the Subes running at 6000 rpm are just not true. Egg runs a max of around 4900, I run 4600 on mine.........."
I stand corrected I was thinking of a Mazda, but 4900 is still almost twice what I turned my Subie car on the freeway. Guys who work for car manufactures destroy engines by running them wide open all the time for a living. Fact is car engines do live at less than 30% of their rated max output most of the time. They only get up to rated HP for short periods. Does it mean they can't do the job in a plane? No, but as you said use of these engines in aircraft is realitivly new. We shall see.

"In fact, any good, modern engine is capable of this. One of my friends raced a stock 4AGE powered MR2 in endurance racing series all over North America........"
Amazing, agree no doubt car engines are reliable. As I said we shall see how the auto engine fleet does over the next 20-40 years and 100,000-million hours.

"Wankel and Sube conversions are in their infancy and there is still much to be learned with redrives, cooling and weight reduction along with ECU tuning, props and blown aspiration............."
Agree, it is all very experimental. You have present facts very well and agree with you. They are improving and my big pet peeve is the cooling drag. Clearly the radiators in an auto engine set up are "add-ons" and work-arounds to the existing RV cowls for air-cooled engines, except the powersport rotary engine cowl, which I think Sam James makes. This is a step in the right direction. Clearly the P-51 had the idea long ago of using a belly scoop and special baffles, ramp doors and "diffusers" to reduce cooling drag. The NACA design paper I think is de-classified and you can get it on the web somewhere?

"Lack of a good, inexpensive variable pitch prop is a major issue with auto conversions............"
Yep, and electrical props will be more always be more cost & maintenance with a slip ring and brushes. Reliability? Hydraulic props are fly them and forget them in my experience. Also aerobatics may not be as satisfying as a hydraulic prop, in that they act much faster. The electric prop may not be able to keep up and RPMs may vary. Again like everything there are limits and trade offs.

"Supporting systems such as fuel, ignition, radiators, alternators and dual batteries receive a lot of attention with auto conversions and rightly so as these cause the majority of "failures"......."
It will always be a concern. It would be a good test to take a Subie or Rotary up and dump the coolant and see if it can last long enough to get you on the ground. Any takers? My family had an early Mazda RX-3 rotary engine car in the 70's. It got overheated once and melted the O-rings. I guess they are better now, but still I don't think they like to be overheated. I would guess if the FAA was certifying a water-cooled engine today, it would have to be shown loss of coolant would cause no hazard, is redundant or it could never happen.


"The atmo Wankels do have the high noise level problem to contend with and much muffler development has taken place. The latest idea is simply to mildly turbocharge them............"
Great idea, look forward to seeing the real experimenters do this unlike us lazy bolt'er-up Lycoming and go fly guys. Even a Lycoming can be quieter with a muffler. The only problem is people don't want a "swiss" muffler hanging from the bottom of the plane half way to the tail. They are about 4 to 5 feet long. In Europe they have no choice, like in Switzerland. I have a 4 into 1 exhaust system on my RV-7 O-360 with a 19.5L" collector. It would be so easy to extend back another 21" with a aluminum or stainless steel round racing muffler. It could be made to remove quickly for speed and replaced for cruising. These off the shelf mufflers are small , light and the correct 19-21" length multiple needed for "tuned" savaging. Once I get my current project flying, I may experiment with this. I think a lot of the "noise" and vibration felt in RV's with a Lycoming is the pounding of the exhaust on the floorboards. It will be interesting to see how much reduction in noise I get and at what loss of speed from the extra appendage hanging down. What about an augmenter fairing to scavenge air out of the cowl. This shows even a Lycoming installation can be improved, such as a sealed pressure plenums (been around for 40 years plus) and small laminar flow cowl inlets developed by the U of Mississippi on a NASA grant in the 70's, first used by LoPresti, like the Sam James cowl.


So experimental improvement is not just not for the auto conversion guys. You can still have a Lycoming and "play" with ideas and be differnt. In the last 10-15 years-Lycoming: 4 into 1 exhaust, better electronic ignition, FADEC, Roller Cams, modified cam profiles, HC pistons, differnt piston ring and cylinder materials, aftermarket fuel injection, **liquid cooling, composite engine oil pan and better engine instrumentation to name a few. The Lycoming is not that old fashion.

Cheers George, big fan of auto engines and builders that try it, but have a Lycoming for now.

**The best thing about Subie and Mazda engines is they are liquid cooled. Liquid does have advantages. The bad part is adapting the heat exchanger to the airframe, especially ones designed around aircooled engines. What if the Lycoming were liquid cooled. Here is an interesting link below.
Cool Jugs-Liquid cooled cylinders for Lycomings

 

[rv6ejguy]

You make some fine points here. I'm not defensive, just one to set the records straight with facts from 25 years of real world engine building/ racing and flying a Sube powered RV. I try to tell it as it plays out, bad or good. I just don't like to read crap put forth by armchair "experts" who have no experience in the field of auto engines or flying them, any more than you want to read foolish propaganda from the auto contingent about how much better auto engines are than Lycs.

Yes, some auto guys slam the Lyc but like you say, there is little factual info to back up the wild claims made by many. I have battled with a couple manufacturers of auto conversion who had completely false information posted on their sites. They have since removed this nonsense.

I'd have to disagree that the Sube is no more smooth than a Lyc. The Egg owners and people who have flown in them- even die hard Lyc owners- say that they are way smoother.

I didn't mention the auto fuel thing earlier. Many guys are running this to save money over 100LL but hauling fuel is not on my fun to do list.

The idea with the Subes is there really is no preventative maintenance. Check the oil and coolant and go, just like a car. Plugs are checked every 250 hours or so and oil changed every 100. That's nice for many.

High rpm use on these engines IS proven with 100,000 flight hours on RAF EJs 4000-5500 rpm, 100,000 km world speed record flat out for 14 days straight at 6500rpm by Subaru and Egg's fleet racking up more hours every day along with others.

I agree that new technology is showing the old dog new tricks (Lyc) and I've seen some pretty amazing reductions in fuel flows when it all works right together. This just puts the bar higher for the auto engine guys. I certainly don't believe that auto engines will take market share from the Lyc in the next 5 years or even 10 for RVs but there are a LOT more people using auto conversions now than 5 years ago. There must be some appeal there.

The cooling solutions are something that we are working on quite a bit. The under- the- cowling rad mounting used by Egg and myself is probably not the best from a drag standpoint but good for packaging and keeping costs in line, especially with the deep spar on most RVs. Our studies show that pressure recovery is poor with such short ducts. We are testing a rear fuselage mounted rad now with flush NACA duct feed and will report our findings on our site. The RV10 project is likely to use a P51 style belly scoop for the rad with cowling cheek inlets to feed the intercoolers. The -10 lends itself much better to the belly scoop due to the central tunnel for running coolant lines.

As long as we all enjoy our flying, it matters not what is turning the fan out front.

 

[Jconard]

I just don't like to read crap put forth by armchair "experts" who have no experience in the field of auto engines or flying them.

Okay, 16 years as a driver and owner in racing. 4AGE engine you talk about is what we use in Toyota Atlantic racing where they spin the RPm you describe, but need rebuilds every weekend to stay in race trim. You are the guy who claims to have built a 1.7L pushrod, 300 hp, turbocharged 4 cylinder, that won 62 races, in road racing, with no rebuilds. Please illuminate the racing series and car number. I have to call BS on that.

I agree that new technology is showing the old dog new tricks (Lyc) and I've seen some pretty amazing reductions in fuel flows when it all works right together.

Again, numbers please the Aerosance Fadec with both ignition and fuel flow gives only 10-15% efficiency boost over the range of operation. At certain points I am sure that there is no gain.


As long as we all enjoy our flying, it matters not what is turning the fan out front.

That used to be true...in the legal environment, a few smoking holes from ill conceived approaches will be the end of us all.

The sube rebuild for that money ($1,000) has got to be rings, gaskets and maybe valve guides, with the owner doing the work.

I can put in rings and guides in lyc for that money.

The $18,000 rebuild price by an aircraft shop includes rebuild of engine and all systems including fuel injection/carb, mags, bearings, etc...and inspection and re-certification of the parts.

In a car engine rebuild you simply measure the parts and send it off to a machine shop. If you could find a machine shop to do that rather than the mandatory replacement/certification schedule that goes with the Lycoming, the cost would be the same.

The only auto engine converted to airplane, and certified was the Mooney porsche. To rebuild a 911 engine to factory standards costs about what a lycoming does...but then it is built to exacting tolerances. There was never a viable busines "blueprinting" the 911 for that reason.

Remember there is an avid busines "blueprinting" the auto engines which is a process that brings them in line with their design specs...it is usually worth 10-15% HP.


There are some principles to engineering which require no data:

1. When given the choice between simple and complex, simple is preferred.
2. Probability of failure goes up at the square of complexity.
3. Heat exchange is never 100% efficient (More like 80%). Therefore the more successions of heat exchange, the lower thermal and drag efficiency. (Metal to air vs. Metal to water to metal to air).
4. Refinement of a functional design nearly always produces better results that revolution. 911 vs. RX-7. The components of the Lyc have been refined and improved with excellent materials and practices for 50 years.

No one has yet explained to me why it is more desirable to spend more for a slower, heavier, higher fuel burn engine that needs more parts and more cooling drag to do it.

 

[rv6ejguy]

Yes, But you don't build engines professionally. I build the car, the engine and race them. I even built my own dyno and flow bench ( and have flowed Lyc and Cont heads on it) and have done over 500 dyno pulls here and on other engine and chassis dynos. I've built over 200 performance street and road racing engines over the last 25 years, many high output turbocharged road race engines. My shop, Racetech Engineering fielded 6 cars in various classes. My company Racetech Inc. currently builds engine management systems, sold worldwide. I am a major contributor to soon to be released the 3rd Edition of Hugh McInnes' Turbochargers book and have written other technical articles for Contact, the forunner of Turbo magazine many years ago and Kitplanes. What exactly are your qualifications in this field?

The Kent Ford engine is crappy OLD engine with the SOHC 2L not far behind. These are cast iron boat anchors. I've built a few and was not impressed with the heads, cranks or anything else about them. You are permitted to do little to these (ie proper race parts) in FF or F2000 so they need rebuilds frequently to stay fresh enough to win. These would not be a good starting point for an aircraft engine and there are many other modern engines today which also would not be good choices to start with.

I mentioned a showroom stock 4AGE here, 112 hp revving to the stock 7500 rpm redline, not a 245hp Atlantic engine running at 10Gs. I have built several atmo 4AGEs, one of which dynoed at 238 hp at 9600 rpm on methanol. This engine WAS highly modified with 12.8 to 1 Wisecos, Group A cams, 7MG valves, under bucket shims, German springs, 4AGZ block and crank, Carillo rods and 50mm SK carbs. I designed and fabbed the header and ported the cylinder head as well.

I mentioned a 360 hp 2TC engine here , not a 300 hp one. I did not say that the engine was not rebuilt in this time. It was rebuilt at the end of each season but we used the same set of bearings, same crank, same pistons, cam, springs, pushrods, timing chain, block and head casting for four seasons. Only rings, gaskets and grinding the valves and seats was required in these four seasons. We ran up to 7600 rpm on these engines if required.

This was run in the Modified Production series here in Canada in the late '80S to mid '90S. Run as a cheaper alternative to GT 1, 2 and 3 on street R compund tires. Turbos were permitted at a 1.5 factor so our 1400cc sleeved 2TCs ran against 2L atmo cars although at a very high weight penalty. Our 1700cc turbos ran against mainly Rx7s and Z cars in MP2. Most days, the 1.4 MP3 Corolla would trounce the MP2 atmo cars in the class above. There was no contest in MP2 where we won the championship 5 years straight, first with a 2TC powered 240Z, then with a 2TC powered Celica. We also ran a 2400cc 20R Celica in MP1 against SBCs. Won this championship the first year and finished 2nd the next year against a $100,000 Camaro with the same $15,000 Celica. In all, we won 7 championships in this series which was the most competitive closed wheel series in Western Canada with sponsorship from Yokohama and then BFG later. The MP2 cars ran similar lap times to the best FF1600s.

I was the chief driving instructor for the WCMA road course licensing school at Race City Speedway in 1992. I was the overall winner of the GT/MP sports car championship with more points than any other driver. No DNFs. I can send you a picture of the plaque if you want.

In 2002, a GTS Corolla running a 1608cc turbo I built, on slicks, took the outright Solo 1 lap record at RCS, running a 1:22 at only 15 psi boost. The GT1 lap record at the time was 1:15.

Anyway, that aside, blueprinting a stock engine will never add 10-15% to the hp.

For our rebuilds, we magnafluxed the rods and crank each season just like the aircraft guys. By the way, all the 2TC engines had stock block, crank and prepped stock rods. The factory hp rating on these engines is 70-88 hp depending on year at 6000 rpm. We made 5 times that! Reliably! Naturally these engines at this output level have a limited lifespan of less than 25 hours but it goes to show that even an old design like this can take some pretty extreme abuse. This specific output would equate to a Lyc O-360 putting out 1245hp! Do you think it would even last 1 second?

I simply advocate choosing a robust, relatively lightweight engine like the Sube EJ or EG series or Mazda rotary, make only the proven internal mods done for racing type reliability, turn it at a conservative rpm (say 75% of the stock redline) with mild boost and it should be very reliable. This is the formula that Porsche and Audi have used to win many 24 hour endurance races. Toyota proved that a 2.1L turbo engine could be more reliable and more powerful (over 900 hp without restrictors) than a 6L atmo V8, V12 or 3.5L F1 type Cosworth in IMSA much to the dismay of the whining Brits at Jag with their unmatched 14 wins in 15 races in GTP (they sat out the 15th race to let someone else have a try). The AAR GTP car still holds the outright lap record at a couple of US tracks I think.

 

[rv8ch]

I love this thread!

Very interesting thread.

 

[RudiGreyling]

Good debate, I feel the tension coming in, we need a break...
go have a look here, for a tension breaker
http://www.bath.ac.uk/~ccsshb/12cyl/

Regards Rudi

 

[Jconard]

Western Canada ...

I thought you said it was road racing. When I was on the circuit, and ran into western Canadians who, like me had travelled to Mosport (In Bowmanville, Ontario), they told me there were not any road courses of consequence in Western Canada...do you mean soe kind of left turn only stuff?

And, the car rebuilds do not require certification and all that goes with it, as do airplane parts. (It would be nice to find an automotice machine shop capable and willing to do the work at the cheaper prices).

As an aside, I read the egg site again. He still does not allow a metal prop. Of course in typical egg fashion he puts the issue as "no airplane should use a metal prop because they are too heavy". It looks to me like pretty good proof that the harmonics from whipping two mettl flywheel arms are too much for the setup...do you know any lasting installations where it flew 1000's of hours with a 60lb metal prop?

 

[rv6ejguy]

I'm gald others are finding this thread so entertaining.

Well RCS is a 2 mile road course built in 1987, Has left and right corners, Has hosted Formula Atlantic, ARS, Players GM Camaro series, Honda Michelin series, Canon/ Yokohama FF 1600 series, and the Yokohama/ BFG/ Reiniking GT/ MP series. It's not oval racing. There was always a big East/West rivalry so the comments that you mention don't surprise me. Mosport is a great track, certainly better than RCS but this is where we race. I'm not towing 2500 miles to go the Mosport. Since Westwood closed over 15 years ago in Vancouver, RCS is the best we have in Western Canada.

You might want to check the HIGH standards that aircraft machine work is done to. "The Aviation Consumer" magazine, July '99 reported "spotty" quality control on valvetrain parts, mostly on valve seats and guides. Apparently in their testing, TAC's A&P found 60% of the heads examined were outside manufacturers specs and many of these were OEM new or remans! Problems included non-concentric valve seats, improper seat widths and excess guide to stem clearance. Any automotive shop machinist understands the importance of a properly performed valve job for engine life and performance. Again, the question begs to be asked, what are you getting for all of this money?

After having customers complain for years about problems with their TCM engines, Beechcraft (Raytheon) has compelled TCM to produce "special improved" engines for installation in their airframes. Customer complaints included excessive vibration, camshaft and cylinder corrosion, low compression and high oil consumption. Let's remember that these are brand new, certified aircraft engines worth in excess of $30,000 each.

TCM's standard and "improved" tolerances for balancing parts are as follows: Crankshafts, counterweights and gears- 21 and 12 grams respectively, connecting rods- 14 and 2, pistons 14 and 2. Combustion chambers are now balanced within 3ccs vs. 8 on standard engines. Japanese automotive engines routinely come from the factory with all of these tolerances under 2 grams and race prepared engines usually have this reduced to under 0.5 grams as weight imbalances have long been understood to reduce life and increase vibration. Chambers are usually die cast or fully machined to less than 0.5 ccs in volume difference between chambers. TCM has implemented many other changes to make the performance and reliability satisfactory which is absolutely routine in the automotive world. I find TCM's standard specs appalling.

Not sure what you are getting at here about metal props. Egg designs the whole package and knows a lot more about this than you do. He has these recommendations because it works. Egg does not allow metal props because 1, the C of G would be way outside the forward limit, 2, he can't afford any more weight, 3, the harmonics are outside the envelope of the redrive and damping system to deal with 4, a variable pitch prop is required with auto engines to achieve proper performance over a wider rpm range, this means electrically adjustable as there is no provision for hydraulics through most of the redrives available which precludes using a Hartzell.

Rotax publishes maximum prop weights and moments of inertia to be used on their engines as well so ensure safety within the limitations of the redrive bearings, gears, case and damping system. The highly developed and tested Powersport Wankel redrives also have specific recommendations on propellers to be used. This is basic engineering. The Marcotte's like I use have no prop weight limitations and have the ability to use a hydraulic prop if desired, however many combinations have not been tested. This is a very important aspect of redrives. If you are a student of history, look at what P&W and Wright went through on developing damping systems for their radial engines. You don't recommend something which may lead to a failure.

I've refuted all your points with facts. Your unsubstantiated treatise does not hold much water and you are exactly what I referred to earlier as an "armchair expert" on this subject. You have not responded that you either are a professional, experienced engine builder or have even flown in an auto conversion aircraft apparently but are attacking what you have no first hand knowledge or experience in.

 

[Jconard]

My earlier point on the cranks was precisely that the egg setup lacked the beef to handle the harmonics of a big metal prop. A lyc crank will do this. You now agree as does Egg, that at least those dynamics, common to aircraft, are beyond the envelope of the egg/sube design. I assume you agree that the crank would be equally insufficient in a direct drive scenario.

This I pointed out earlier based on my experience with VW conversion which can only use a wooden prop, even when, as I pointed out earlier, they are fitted with SCAT cranks (solid chromoly forgings). You now agree.

You also agree that all of those conversions are equally unable to tolerate the harmonics and weight of a metal prop. Again my earlier point about crank size was exactly that point.

Allow me to offer a quote from an erlier post:

"The aircraft crank is beefy to handle resonance and gyroscopic loads from the prop. Remembber that a prop is a 60 lb pair of flywheel arms that are constantly accelerating and decelerating. This adds torsional stress and harmonics that an auto crank is not able to handle. This is why the VW conversions, even with chromoly scat cranks, (far stronger than a sube crank, often used in alcohol midgets), still can only use a lightweight wooden prop."

You also already agreed with the slower, heavier, and thirstier issue, but offered smoothness and simplicity as compensating.

As to my personal experience, as a driver and team owner I bought and raced professionally built formula cars engines, including as high as the atlantics. I helped friends build japanese drag race engines, and am familiar with the 20R, 24 R, and 4AGE engines as well as the early inline 6's from Datsun. When I was younger I built dozens of porsche club engines, and VW aircooled engines for off road racing or drag racing. Built Type 1, Type 4, Porsche type 4 and 911 engines. As an aside, very few shops in north america, for cars have the ability to grind even a 911 crank.

I have been a part of countless dyno and track test sessions...although as time wore on more of the wrench work was done by others.

You throw out alot of anecdotes about spotty TCM quality, but never circle back to a few facts: A lycoming will run for 2000 hours, and a specific efficiency you admit you cannot achieve, and do it with less fuel and less weight, and fewer systems.

Assume for a minute that I am an ignorant armchair guy. Teach my why I should disregard the following engineering maxims:

1. Simple is preferred to complex
2. Probability of failure increases at the square of complexity.

Please also tell me, as you haven't, why the complexity of engine management is necessay in a fixed rpm, almost unvariable rpm scenario. If you answer that question, pplease do so in a way that accounts for the lower actual efficiency that seems to be achieved by these systems in the world?

While we are on it, you also have not given a reason to prefer a system which constantly circulates high volumes of fuel, at high pressure, through the cockpit and back to the tank. You mght say vapor lock...but the only RV I know of to go down on a flight from Vapor lock was a sube.

The applications are so different it seems that all the "experience" you claim to have is taking you in directions that are simply unwise in an airplane. Tht is why I will not fly one.

 

[rv6ejguy]

I'm afraid your logic escapes me on the propeller, bearing thing here. These are in fact auto engines, not originally designed to power an aircraft. I think most people understand that. The redrive is required to drive the prop at an efficient rpm while allowing the engine to produce its rated hp at roughly double the prop rpm. The redrive also handles the thrust and gyroscopic loads. Direct drive auto engines don't exhibit a suitable power to weight ratio in most applications. Its just the nature of the beast.

I think you will find that most auto conversions use a composite prop for the reasons previously listed. Is there some reason why you would want to use a metal prop specifically against the recomendations of the powerplant manufacturer. I don't understand.

I think the previous posts list the advantages and disadvantages of the auto vs. Lyc and why dozens of people are choosing auto conversions despite some disadvantages. No point to rehash this.

Sorry, not familiar with a 24R engine. Toyota never offered such an engine in North America. I think you mean 22R which powered trucks and Celicas for many years.

We now match the SFC of the O-360 at .42 lbs./ hp/ hr. Weight is and always will be higher with an EJ22T than an O-360. No dispute there.

A Lyc CAN go 2000 hours between major overhauls but they don't always. Many require top end work long before this, especially if flown infrequently. The Sube and Wankels typically need no work done internally for at least 1000 hours and we are heading towards the same 2000 hour TBO with many engines here. You don't have the oil consumption, valve adjustments, sticky valves, head and jug issues that sometimes show up on certified engines.

The post where you mention the Sube crank quality is not mine. The EJ22T crank is forged alloy steel and heat treated from the factory. Likely better quality than the SCAT forging. We see NO failures on Sube cranks. Not ever even turbocharged at very high outputs. Rods are forged alloy steel as well, again NO failures. Unlike some Lyc cranks I might mention.

Sube engines all come with EFI and direct fire ignition. These are proven to be more reliable than carbs and magnetos because they have less moving parts. Apply your own law here. No rotor, no points, no shaft or gear drive, no venturi to ice up, no float arm to break, no needle and seat to stick. MTBF of the OE ECU is in the millions of hours. I've worked on EFI engines for many years and see lots of German and Japanese vehicles with the original everything in them over 20 years. Pump, injectors, sensors and unfortunately even fuel filters which people neglect to change. Not only that, since there is almost nothing moving, there is virtually no maintenace. Emissions dictate EFI for their intended mission.

Would you actually take the factory developed EMS off one of these engines and stick on twin mags and a carb? This would be undoing millions of dollars worth of engineering, development and testing to make it less reliable. I don't understand!

You have fuel in an RV, right between the pilots even with a Lyc. If the fuel valve breaks on a line ruptures, you will have a cockpit full of fuel and no way to stop it. EFI requires high pressure pumps. No way around that.

Vapor lock on the one Egg plane resulted in a recomendation to use 100LL above 12,000 feet I think plus a redesign of the pump/line layout and heat shielding I believe. Someone with an Egg can correct me here if I'm wrong. Remember we are still on a learning curve here.

Like I said, fly your Lyc and enjoy it. The others who want a Sube or Wankel will hopefully be happy. Different strokes for diffrent folks.

 

[thallock]

This is an interesting thread, but has started to degrade somewhat, as would be expected with the subject matter. It is pretty apparent, that this is a deeply divided issue, and one side is not likely to sway the other side much at all.

The original premise was that if you plan on using an auto conversion in your RV, then you should expect to be a test pilot. Well, I cannot agree more. Of course, with any homebuilt aircraft, you can expect to be a test pilot no matter what engine you put in it. That's why the FAA makes us fly solo for 25-40 hours. I know, I know, that's not the real issue. The real issue is that with an auto conversion your're going to be more of a test pilot, and for a longer period of time. Well, maybe yes, maybe no.

As far as I can tell, there really aren't that many all-in-one FWF packages available for RVs. You know, the package that you just bolt on to the front of the airplane and fly. With all of the different variations and options with Lycomming and Lyclones, just placing the order is an ordeal. No, the only all-in-one package that I know of is the Eggenfellner. Probably, the most complete package that you can get. Proven? Well, we won't know until enough people give Jan their money, and fly around for awhile. Until then, people will continue to try and make their own decision look right by jumping on every single glitch in the Eggenfellner package, and any other auto conversion out there.

I would contend that we are all test pilots. If you don't want to be a test pilot, then you probably shouldn't be building an airplane.

BTW, I'm not going to use the Eggenfellner conversion--too expensive. I really do want to be a test pilot, so I am putting together a rotary conversion. Thanks George.

Cheers,
Tracy.

 

[RudiGreyling]

Let's get back on subject!

This is an interesting thread, but has started to degrade somewhat, as would be expected with the subject matter...
Tracy.

Ditto, Tracy, I have been following and learning a lot, but the last couple of posts degraded a bit. I still like the thread, and think it is valuable to newbies.

So Please let us get it back on track, let us talk subject and not person!

Another interesting picture to BREAK the TENSION:
http://www.bath.ac.uk/%7Eccsshb/12cyl/

 

[rv6ejguy]

Love these photos of these HUGE engines. Amazing!

 

[Mel]

If your put an engine like this in your RV, you will definately have to move the battery aft for cg...waaay aft!
Mel...DAR

 

[ship]

doesn't look like the technology has changed a whole lot in 75 years. can't resist stirring the pot

not sure my torque wrench can handle those head bolts...

 

[EridanMan]

Hey Guys... Great thread (hooked another newbie)...

I have a feeling this website is going to end up being very bad for my pocketbook/spare time... (I've been thinking about starting a build and I'm doing a bit of research)...

Anyways... I am a bit of an engineer, and I have to say when I heard about putting a Wenkel into an airplane, a little Bell went off in my head...

I agree with what most of you say - when it comes down to it, lycomings are over-engineered in all of the places Airplane's need to be... They're simple, reasonably light, and probably the best bet...

Except... the Wenkel has never really made a good car engine, but there is no doubt that it is an amazing peice of engineering. I can't help but think that, fundamentally, its about as close as you can get to a 'perfect' aviation engine.

A- Lightweight block, small displacement, the Wenkel block is actually significantly lighter than a lycoming flat four... yes, you do need the support equipment, but perhaps a purpose-built aviation wenkel could solve this by integrating a cooling pump and other support equipment into the block.
B- Tiny cross section, great for aerodynamics.
C- No vibration, easy on the airframe
D- Damn-near Zero inertial stress... theoretically Wenkels should be about as reliable as a turbine, if engineered well.
E- Failure mode... Reciprocating engines Cease when there is a critical failure... rotaries just tend to loose power/efficiancy, there are no masses to 'lock' the engine... this is true even in catastrophic overheats.

I guess what I'm saying is... i've heard a great deal of discussion about the flat subie engines... but not so much about Rotaries... Theoretically, they seem to be a great idea... How are they working out in practice?

Anyone here fly a rotary?

(I saw the powersport comparison post, but I couldn't find a source article)

Thanks for the great post, i'm going to crawl back into the woodwork and read now

-Scott

 

[rv8ch]

Rotaries

I guess what I'm saying is... i've heard a great deal of discussion about the flat subie engines... but not so much about Rotaries... Theoretically, they seem to be a great idea... How are they working out in practice?

I guess this thread is getting too long. Rotaries have been discussed, and there are a couple of solutions.

http://www.rotaryaviation.com/

http://www.mistral-engines.com/

One thing I think you will find causing many people to look very closely at the Subaru is that there are three companies competing for the firewall forward RV market. I've got the Eggenfellner package for my RV8.

 

[EridanMan]

I'm sorry, I had read through the thread (granted at 3 in the morning), but I had only noticed a passing mention of rotaries...

I guess I'm just surprised that the Subie Boxer is considered the more 'common' alternative engine (don't get me wrong, I have a huge amount of respect for them... mostly from challenging STi's at the autoX course), the rotary just seemed more 'aviation' to me...

I'll do some more searching of archives here to answer my question...

thanks for the thread, in any case
-Scott

 

[cobra]

Just a note of concurrence- I also feel the Wankel is a far better design for aircraft than old fashioned air-cooled reciprocating monoliths . The only downside involves quick emergency reapirs at an airport, IF they ever break (unikely occurrance, that is why I like them).

Upside: excellent power to weight, cheap to purchase and rebuild, very smooth running, low internal part stress, reasonable fuel usage, small shape, uncommon.

Downside: uncommon, parts difficult to find, noisy- best muffled with a turbocharger.

 

[ship]

Except... the Wenkel has never really made a good car engine, but there is no doubt that it is an amazing peice of engineering.-Scott

isn't this a curious contradiction?

why didn't they didn't make good car engines?

what makes them better for planes if they didn't succeed in cars?

interesting article in previous RVator re the rotary flyoff at Van's....notice the fuel comsumpion of the rotaries compared to the lycomings.....like 40% worse. ouch.

 

[cobra]

Im no expert on the rotary design and I have not formed a bias for any specific motor design yet, but here are some possible answers to your questions:

why didn't they didn't make good car engines?

Same logic- why don't Lycomings/Continentals make good car engines, or possibly closer to the argument, why don't turbines/jet engines make good car engines. What difference does it make- we are not talking about flying automobiles.

Actually, I believe the real reason is twofold- 1.) the Wankels are only offered in one sport car model, and it has never been particularly available- low production numbers normally mean higher comparative costs in the auto world, and price rules the mass manufacturers decisions, and 2.) there are any number of other production engines in the automotive world that produce as good or better torque numbers at lower rpm.

Also, the Wankel design was introduced during the oil shortages of the late 70's, which didn't help. It runs more like a 2-cycle than a 4, and it will burn more fuel than a 4cycle equavalent if compared by displacement (not power output). The HP comparison should be with a small v-8, not a 4 cyl econobox. Recent updates to ports/seals/timing/electronics have helped the fuel burn rates and performance from early designs.

To be fair, the Wankel engines are very popular with enthusiasts who race and know how to run them- huge HP available and very reliable as far as race engines go.


what makes them better for planes if they didn't succeed in cars?

Light weight with excellent weight to power ratio; water cooling allows tight tolerences and long life; smooth running; best when running at high rpms for long periods of time (cars spend most of their time at 2000-2500 rpm, not 4500-5000 rpm). These engines really only have 1 moving major part like a jet engine, and it acts more like a gear than a piston/rods/valve train.

As to the high fuel consumption- the burn rates are actually very similiar depending on how the tests are structured and how the fuel systems are set up. You need a set amount of fuel to produce power (approx 0.5gph/hp) , and you need to provide a rich fuel to air ratio to keep the head temperatures low, more so with air cooling.

The numbers Ive seen suggest ~5.5 gph at cruise for a 200 HP engine. Either engine can be leaned for cruise but not for high power production- the difference is that the Lycomings/Conts need to be leaned manually (inaccurately?). The Mazda has fuel injection/ computer engine management available to set timing, fuel ratio, and altitude compensation. The Mazda also should not overheat as easily as a leaned out, air-cooled engine might.

The rotary certinly is not the only good aircraft engine design option, but it is probably better (IMHO) than any recropocating design and is a viable, cheap subsitute for high durability, lower-powered applications than the current turbine/jet engine market makes available to us.

 

[EridanMan]

cobra... you hit basically everything.

The only other thing to add is failure mode...

Nothing short of complete fuel starvation (or total electrical failure) will cause a wenkel to completely die... overheat the engine, and your seals will break down as you gradually lose power... loose lubrication? same deal... I've read reports online (in the past week) of Flying Wenkels loosing their cooling systems, only to make it all the way home by running the engine right up at his thermal redline for almost an hour with no danger of it seizing on him (granted, I wouldn't want to have had to be the one to rebuild it afterwards).

 

[gmcjetpilot]

Rotary-noisy, thursty and installed weight more

The rotary certainly is not the only good aircraft engine design option, but it is probably better (IMHO) than any recpocating design and is a viable, cheap subsitute for high durability, lower-powered applications than the current turbine/jet engine market makes available to us.

Rotary engines are great but noise, fuel consumption and installed weight are not the pros and never will be, no matter how cool they are. Recent heads up flight test with two rotary powered RV-8s against Van's demo 180HP RV-8 says it all. Rotaries burned more fuel, are louder and weigh more (ref. Van's RVator).

Comparing weight you have to go by installed weight, not the weight of a stripped down short block.

Performance: Finally at least the rotary had equal performance to the Lyc/Hartzell RV. T

Cost: The Rotary engines were custom installations, cowls and cost more than an O-360/Harzell combo. Not sure if a homegrown Mazda B13 would have as high as performance as the custom modified powersport rotary engines. A Hartzell prop is about 5 grand. The MT electric C/S props on the rotary engine RV's are about 10 Grand!

Water-cooling is great if the aircraft is designed for it with fuselage or wing mounted heat exchangers like a P-51. Till now most water-cooled auto engines have setups that look like an after though or a work-around to adapt to the original air-cooled installation design. Oh, yes, water-cooling weighs more and is more complex.

Look, all the talk in the world will not override numbers and actual side-by-side comparisons. For the same performance, with more noise, fuel and weight and complexity does not sound like a leap forward, just different. As I have said, if you want to go flying, put a Lycoming in. If you want to tinker, invent and experiment (a lot), put in an auto conversion.

Cheers George

 

[cobra]

Good points, possibly valid, but hardly conclusive with only 4 units compared with so many configurations possible. I have not read the RVator article, so I cannot comment on it- is it available somewhere? All I can say is that your summary contradicts other comparison reports, so there should be reasons for discrepencies.

The Rotaries can be noisy for sure, but the jury is still out on how best to muffle a rotary motor without degrading performance. The air cooled motors are loud too when short pipes are used.

The weight issue is subjective- it really depends on how the motors are set up, how they are cooled, what batteries/generators used, etc. From what Ive seen, the weight issue is pretty much a draw (can be slightly heavier or lighter).

Questions concerning the test setup::
Which generation motors were used (there are at least 3 of them available from Mazda, each better than the last)? Were the 300-400 HP rotaries ignored for comparisons or just the early models that produce around 160 HP in stock form? Were turbocharged rotaries included (they are significantly quieter than straight pipes and obviously produce more power). Rotaries love turbocharging to improve mediocre air scavenging tendencies when normally aspirated.

If you want to compare fuel burn rates, make sure the comparison is fair- (include temperature parameters, same power levels, etc). Id like to see how the Rotary fuel systems were set up- carburated or fuel injected, how/when were they each tuned prior to the test, and what were the test parameters (was one type favored, biased test structure)... those kind of variables.

I do agree however, that a head to head test is a very good way to compare as long as the tests are unbiased. As a minimum, this test compared a very mature design with one still in early development, so the conclusion is not surprising.

"As I have said, if you want to go flying, put a Lycoming in. If you want to tinker, invent and experiment (a lot), put in an auto conversion." That statement makes about as much sense as saying air cooled engines have killed more pilots than other aircraft engines- probably true, and misleading.

My attitude is simply, if it works, chose the best alternative based on durabilty, performance, and cost in that approximate order. My best guess is that a rotary will outlive any reciprocating air cooled engine of equal power output, several times over at a fraction the cost- because they have far less mechanical internal stresses and they are manufactured in commercial aquantities to keep costs in check. BTW, if it were not for tinkerers, we would still be walking everywhere, living in caves, and cooking around campfires. Technology evolution is desirable and inevidible.

 

[leeschaumberg]

Good Modern Aircraft Engine

A good modern, efficient, and powerful aircraft engine in the size needed does not exist today. Many people say this and say that, but the former holds true. A person that claims fuel consumption at cruise means nothing to me. Fuel consumption is determined by pounds of fuel burned and the horsepower produced. (BSFC) This corrects horse power and fuel consumption to a standard temperature.
A good fuel for tomorrow does not use any thing made from anciently decomposed plant and animal matter. Oil made from newly grown plants and hydrogen. With these two we can run and fuel every thing in use today. The octane and cetane of these two is very good.The aircraft engine of tommorow will not use spark plugs.
With the millions of people working in the oil business and the trillions of dollars in the oil business it will take a while to change.
Lee

 

[gmcjetpilot]

Big fan of Mazda/Wankle engines

Cobra:
I think the rotary in the 150-200hp range is one of the better alternative engine choices. Even the Subies with turbo charges have shown that they have acceptable operations. All these engines are not quantum leaps but simply an adapting an internal combustion engine, with all the same limits imposed by the laws of physics a Lycoming has. Unless it is going to be really lighter, faster, more economical, easier to install and maintain, for me, the old fashion way (Lycoming) is still the only choice for me.


I agree with you 100%, the tinker and inventor are the ones that make the way. Orville and Wilbur Wright where homebuilders, right. The "adaptation" of auto engines auto engines and water-cooling was done over 70 years ago with the Pietenpol Aircamper in the 1930's, with a Ford model-A engine.

To over come the big disadvantage of a Lyc, I bought a good core cheap (got lucky) and overhauled it myself (total cost for O-360, $10,000). To keep maintenance down I operate with the limitations and fly often (dis-use is the killer of engines). As far as fuel burn I can throttle back and poke around at 160 MPH instead of 195MPH on less than 7 gph. Plus I get to use a cheaper Hartzell (hydraulic) vs the more expensive electric props with their maintenance disadvantages. It would be nice if the inventors would make a reduction unit for a Rotary engine with a hydraulic c/s prop set-up.


Cheers George

 

[cobra]

GMC
It is the laws of physics that give the rotaries a big advantage. A lot of energy is wasted speeding up and stopping heavy pistons, rods, crankshafts, camshafts, valves, rocker arms, etc twice during each revolution of the motor. That energy pounds bearings, produces heat and friction, and generates vibrations that fatigue metal, break parts and shorten engine life. The loose "stacked" tolerances required in an air cooled motor only make the wear and vibrations worse.

The rotary operates more like a turbine than other motors- the pistons/rotor rotates in a continual radial motion, no slapping valves or camshaft drive losses, high rpms available if desired, near-continual and smooth power push vs power pulses pounding each head and crank bearings every second revolution.

Orville and Wilbur were bikebuilders. One of their biggest (most important) inventions was the light-weight motor they made to power their aircraft; funny noone mentions that fact.

Your point about hydraulic c/s props is a biggie in favor of Lycs. Im thinking that I'll compensate to some extent by using either a cruise or 3-bladed propeller on a turbocharged and ported second gen motor (w 240 HP on tap) for climb/takeoffs. The high rpm capability and extra torque should help to some extent (6000 rpm available without adding undue stresses).

 

[EridanMan]

Just make sure we deliniate here between 'practical' and 'theoretical' ideal engines...

Currently, the best, easiest, simplest and probably fastest solution out there for builders who wanna 'go now' is going to be a lyc... simple as that. They're proven, they work, they work well, and god knows they've got a pretty good 50 year track record.

But... That doesn't made them the ideal aircraft engine... They might be the ideal 'right now' solution, but their design is _far_ from perfect. They are, fundamentally, a 50 year old 'patch' do a design (flat-4 reciprocating) that is fundamentally bad at producing full power for long streaches of time.

I'm reaching back here (so if I'm off, don't sue me), but IRC, a reciprocating engine's internal stresses scale exponentially with the preassure on the pistons (power produced)... this is exascerbated by the high-torque, long through nature of a Lyc... Lyc has counteracted for this by creating an engine that has reinforcement in all the right places... but the engine runs under such high stresses that it requires constant oil changes, constant lubrication (running), and it produces several very undesirable side effects (vibration, huge frontal area)...

I guess I've noticed a kinda Lyc 'religion' on here, where because its been around for 50 years, obviously its perfect... this is, of course, ludicrous... Lyc engines are like Porsche 911 race-cars... Bad ideas that have been brilliantly implemented so that they work well...

Yes, they work great... yes, they're going to work quickly, easily, and reliably, and yes everyone will fix one... They're probably the optimal solution at the moment... But to say that the aircooled, long throw horizontally opposed air-cooled engine configuration is somehow the end-all and be-all ideal for aircraft propulsion is... well, kinda ludicrous.

I think the biggest problem is just that the GA market is so small, its not worth the investment for most companies to put any time, energy and effort into developing for it (especially since it sat stagnat for 30 years)... Lets home Experimental's succeed in breathing some life back into it.

All Cobra and I were saying (I believe, don't mean to speak for you, Cobra) is that, on a theoretical level, the Wenkel configuration is a far more 'ideal' solution than the long-throw horizontally opposed engine... It is just fundamentally more suited for light-weight, highpower for extended periods of time. Am I necessarily talking a B13 or B20 conversion? not at all (although rotaryaviations planes are reasonably impressive, and I know I read one guy who had a flying Mazda engine for a 5200 dollar total investment (salvaged/rebuilt block and turbo)... not bad for a 180hp engine... But, probably requiring a hell of a lot more specialty rotary expertise than I have.

I (like the rest of us, I'm sure) will be watching the aviation powerplant market very closely over the next 5 years... It'll be interesting to see where the very-small-turbines end up... On a theoretical level, a Turbine is just about perfect for an aviation application... the question will be can they keep manufacturing costs and fuel-usage low... On the other hand, a Wankel offers 80% of the advantages of a Turbine, with far lower production tolerances needed (no need to spin at 61k rpm), and theoretically less fuel use needed as well. perhaps it's a better comprimise?

Modern short-throw auto-engines (with reduction gear) is another decent solution, the trick is keeping the power-to-weight and complexity issues under control... (as well as making sure they're ready to operate at 95% for 6 hours at a time)... I'm not holding my breath there, but it wouldn't be the first time I was wrong.

I guess all I'm saying is... Lycs are a great choice... they're going to run, they're going to be relatively easy to install, and they're going to be reasonably fuel efficiant and easy to service. If I was putting an engine into my plane next week, Its probably the best choice...

But... I'm not... and Lyc's are far from perfect... So I'm going to wait and see if anything more interesting comes down the pipes...

Simple as that

 

[gmcjetpilot]

Theory vs. Facts

GMC
It is the laws of physics that give the rotaries a big advantage.

Again in theory it is great, but the proof is in the pudding (or is it the dismembered finger in the chili?) A rotary is still squeezing gas/air together and burning it. I don't see a big advantage, only differnt. Anyone who is interested in rotary engines should read everything they can. Tracy Crook of (RWS) Real World Solutions is a straight shooter and shares the pros and cons in a straightforward way, with out too much hyperbole. The cons of the rotary are well documented by RWS. One is gas mileage. I talked to a RX8 car driver at the gas station and he said it was great, but......... it gets horrible gas mileage and has no low-end torque. It has a listed 18/24 MPG city/hwy mileage , but is is closer to 15/21 MPG, real world.

Tracy addresses fuel burn and the noise problem. My feeling is all these cons are OK, even the higher installed weight is OK, if it provided clear performance advantages (read speed, climb...). At this time they do not, but they are getting better. We shall see; may be the new RX8 renesis engine will be a rocket in planes? it does have better performance will it be enough to outweigh the down sides. And oh yes, LYCOMING RULES

Regards George