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RV-6A Real World Numbers

pilotmansam

Active Member
I am looking for some real world performance numbers for a 150hp RV-6 or 6A. I have the CAFE report for the 6, but that is an O-360 constant speed prop. I do not need such an exacting report (but if one exists that would be nice!). I simply wish to compare approximate real world numbers. I realize there are numerous factors here (prop, weight, etc) but I am just wanting to get a ballpark comparison. Any help?
 
Why don't you post the numbers you are getting with your RV (and prop, rpm, and weight) and we can see if they fall into what is expected. Also, are all fairings installed cleanly on your RV?
 
Van's book speeds for the 6A
https://www.vansaircraft.com/rv-6/#aircraft-details-2

Quotes 150HP as 185 mph at 75% cruise speed.
From my experience, the 160 HP number is accurate... BUT only if you have the right prop, and no rigging issues, and no excess cooling air bypassing the baffles, the later style wheelpants, etc. I've worked on my plane for 4+ years after the build tweaking things and now I do get the book speed. Also you aren't going to get the book speed on a fixed pitch prop if you aren't willing to see rpm above 2500.

Also those numbers are a lot more achievable if solo, and the plane isn't weighed down with a lot of 'extras'.
 
I fly an RV-6A with an O-360 with a constant speed prop, but standby.
We see 155 KTAS at around 60% power and 10,000 MSL.
That's 108 hp. If I exchanged the O-360 for A 150 hp O-320 and ran it at 72%, that would yield 108 hp and approximately the same speed.

As Philip said, "Do forum search and you should get quite a few hits."
 
Can’t help you with 150hp numbers but at full gross including 100lbs of baggage we get around 165 knots true between 9500-12,500 ft. Full power and 2400rpm leaned to 7.2-7.5 gph …….lean of peak around 6.5gph we get around 157 knots
Flying around 3500-4500 ft we get closer to 150-155 knots leaned to 8+gph.

It’s an IO-320 with constant speed on a 6A with an empty weight of just over 1100 lbs.
 
Van's book speeds for the 6A
https://www.vansaircraft.com/rv-6/#aircraft-details-2

Quotes 150HP as 185 mph at 75% cruise speed.
From my experience, the 160 HP number is accurate... BUT only if you have the right prop, and no rigging issues, and no excess cooling air bypassing the baffles, the later style wheelpants, etc. I've worked on my plane for 4+ years after the build tweaking things and now I do get the book speed. Also you aren't going to get the book speed on a fixed pitch prop if you aren't willing to see rpm above 2500.

Also those numbers are a lot more achievable if solo, and the plane isn't weighed down with a lot of 'extras'.


I have a 6 with 150hp and a fixed pitch wood (Sterba) prop. With all fairings on, solo, with full fuel I regularly see somewhat less than the Van's number (155kts IAS, corroborated with GPS GS) in smooth air WOT at 8000 ft which is probably about 75% power. Never did the detailed power calculation, or carefully flew multi-leg test flights to evaluate TAS more accurately, so the error bars on my speed are probably +/- 5 kts.
 
I fly an RV-6A with an O-360 with a constant speed prop, but standby.
We see 155 KTAS at around 60% power and 10,000 MSL."

My son and I just bought an RV6A with 180HP 0-360 and Hartzell CS prop. He is using it to build tach time for a planned professional career and would love to figure out if there is a prop/Manifold Pressure setting other than 24 squared that minimizes fuel burn without pushing cylinder head temps out of the desired range of 320-400F. Speed is not important on the days he's simply flying local to build time.

Unfortunately, our plane doesn't have a fuel flow meter (which someday I'd love to add if it's feasible). Would love any insights you or anyone else here may have regarding best economy power settings.
 
Building time? Fly max endurance speed.
Max range speed should be around 92 knots.
Watch oil temps at these lower speeds.
Need to get somewhere a little faster? Try Carson speed - 121 knots
Lean to max EGT (Lycoming recommendation for O-360)
Try 1900 rpm, if that's rough, try 2300 rpm - staying out of the Hartzell no-no range.
https://www.yumpu.com/en/document/read/34671047/aircraft-performance-report-rv-6a-cafe-foundation

Thanks for the link. Any insight regarding how to set the manifold pressure for either the 92 or 121 knot suggestions? Honestly things were simpler with our flying club's fixed pitch prop planes that had fuel flow meters. I'm not convinced that the CS prop does much except give us a faster climb - which we really don't need. Wish we could easily add a fuel flow meter.
 
Your CS will give you faster takeoff and better climb and allows you infinite settings on cruise….:). the downside is cost and long term maintenance
 
The short version is get that manifold pressure back to 22" or below, grab that big red knob, pull it out until the engine stumbles, then richen slightly until smooth.
I have essentially the same engine as you (but with injection and EI) in a similar airframe (-7) and leaned out at 8,000' it will do 163kTAS on 7.6GPH. With that red knob pushed in to 100deg ROP, it does 171kTAS for 11GPH. ROP is totally not worth it for cruise. May as well be throwing $100 bills out the window. Lean of peak your engine will run cooler and cleaner, and you'll make the oil barons poorer. What's not to like about that? For building time, the aircraft will still fly great back at 5.5GPH and 120kts, so long as it's LOP.

For more detail on all of this, you really need to read the Pelican's perch articles by guru John Deakin. Undoubtable the most comprehensive information you can find on this topic.

https://www.avweb.com/features/avweb-classics/pelicans-perch/pelicans-perch-index/

https://www.avweb.com/features/avwe...-65where-should-i-run-my-enginepart-3-cruise/

https://www.avweb.com/features_old/pelicans-perch-18mixture-magic/

If you're thinking along the old school 24 square lines, you're probably also running AVGAS still. I wouldn't let that stinking stuff near my engine. There's a reason you don't put it in your car anymore. Read the article below and go buy yourself some ethanol free high octane mogas.

https://www.avweb.com/features/pelicans-perch-55lead-in-the-hogwash/

Your engine is on this list somewhere, and approved for 93AKI. Just be ready to use your electric boost pump when climbing on hot days, especially if you leave your aircraft in the sun which may heat the fuel, as the vapor pressure of auto gas can be quite different to AVGAS. Another contributor to vapor issues can be high oil temperatures, as the mechanical pump is bolted to the engine and can heat the fuel before it reaches the mechanical pump. Either way, having the boost pump on hot days during high fuel flow events takes care of things.

https://www.lycoming.com/sites/default/files/SI1070AB Specified Fuels.pdf

Good luck.

Tom.
RV-7
 
You're totally overthinking the fuel flow meter. I have a stupid amount of money tied up in avionics and engine monitoring, but frankly now I just use the red knob and listen to the engine, and use the airspeed indicator. When you are LOP for a specific RPM, for a certain fuel burn, you will get a specific IAS, as all the fuel is getting converted into horsepower. Rich of peak, this is not the case, as a lot of fuel is going out the tailpipe unburnt, and the rate will be highly dependent on the mixture setting. If you run these engines below about 22" of MP, there's not a lot you can do to blow them up, so get up there and go fly LOP. Pretty soon you will know for what IAS how much fuel you will be burning, so your airspeed indicator will essentially become your fuel flow meter. If you keep your testing low, there will be bugger all time spent on climb and descent, so what you used on an hourly basis in cruise will pretty much reflect the burn rate you calculate at the pump at the end of the day. This will give you something as useful and more accurate than most fuel flow meters, not to mention that the off-the-shelf calibration of most fuel flow meters is terrible, so you have to calibrate them anyway, or not trust them. Regardless, your son has to build hours, so it may as well be spent doing something useful.

Tom. Again.
 
You're totally overthinking the fuel flow meter. I have a stupid amount of money tied up in avionics and engine monitoring, but frankly now I just use the red knob and listen to the engine, and use the airspeed indicator. When you are LOP for a specific RPM, for a certain fuel burn, you will get a specific IAS, as all the fuel is getting converted into horsepower. Rich of peak, this is not the case, as a lot of fuel is going out the tailpipe unburnt, and the rate will be highly dependent on the mixture setting. If you run these engines below about 22" of MP, there's not a lot you can do to blow them up, so get up there and go fly LOP. Pretty soon you will know for what IAS how much fuel you will be burning, so your airspeed indicator will essentially become your fuel flow meter. If you keep your testing low, there will be bugger all time spent on climb and descent, so what you used on an hourly basis in cruise will pretty much reflect the burn rate you calculate at the pump at the end of the day. This will give you something as useful and more accurate than most fuel flow meters, not to mention that the off-the-shelf calibration of most fuel flow meters is terrible, so you have to calibrate them anyway, or not trust them. Regardless, your son has to build hours, so it may as well be spent doing something useful.

Tom. Again.

I agree with you Tom, with a slight twist. I'm in the same boat on being able to lean without FF or even EGTs. Pull the knob back, get the stumble, richen up to get a smooth running engine and you're good. The twist is without the engine monitor and having no idea what the engine was "feeling" I was worried about getting lean and ending up in the "red box". After using all the engine data and leaning for a dozen or so flights I'm now able to just pull the red knob back, set to a specific engine smoothness, RPM and speed and only use the engine data to verify things are good once speed, RPM and temps settle down.
 
ROP is totally not worth it for cruise. May as well be throwing $100 bills out the window. Lean of peak your engine will run cooler and cleaner, and you'll make the oil barons poorer. What's not to like about that? For building time, the aircraft will still fly great back at 5.5GPH and 120kts, so long as it's LOP.

I really appreciate the suggestion and links regarding running Lean of Peak. We'll read through them tonight. I'd always been taught with our previous flying club planes (Archer & 172) to use ROP and have always been worried about LOP from an engine damage standpoint - but am willing to give it a try since so many here appear to do it. Hope we get it right! :)

Your engine is on this list somewhere, and approved for 93AKI.
None of the airports we use sell MOGAS (93AKI) so that likely isn't a option for us right now. However, I will see if our carbureted Lycoming 0-360 A1A is approved in case we ever have access to MOGAS - but does switching fuels require some modifications or can we move back and forth between MOGAS and 100LL if MOGAS availability is spotty? Obviously, I have a lot to learn as a first time plane owner! :)
 
I really appreciate the suggestion and links regarding running Lean of Peak. We'll read through them tonight. I'd always been taught with our previous flying club planes (Archer & 172) to use ROP and have always been worried about LOP from an engine damage standpoint - but am willing to give it a try since so many here appear to do it. Hope we get it right! :)


Mike B has a great webinar on YouTube about lead of peak operations. Watch it a couple times, if you use an iPad in the cockpit you can download AircraftPower app for free and based on your engine model it will give you % of power based on altitude, OAT, RPM and MP. I use this to see where I end up on the Redbox scale, then lead enough to stay just outside the safe operating limits, then back that up with verifying my CHTs are within limits as well. After doing this a bunch, it now comes down to a big mixer pull to the far lean side then richen up to get the speed I want and the CHTs that keep the engine happy.
 
I've started reading the linked articles and am quickly realizing why so many people just fly 24 squared - because honestly much of what the author is saying is going over my head - and I used to think I was somewhat mechanically inclined. :) Even if I could figure out the right way to use the LOP methodology I'm not even certain I can trust the CHT readings on our recently acquired RV6A enough to depend on them to do LOP without engine damage.

I'll continue reading but for the time being I think we'll just fly at the usual 24 squared settings that the previous owner and most people I've talked with recommend because nobody I've spoken with has been able to provide an alternate setting that is known for lower fuel burn (even at lower speeds).
 
;)
I've started reading the linked articles and am quickly realizing why so many people just fly 24 squared - because honestly much of what the author is saying is going over my head - and I used to think I was somewhat mechanically inclined. :) Even if I could figure out the right way to use the LOP methodology I'm not even certain I can trust the CHT readings on our recently acquired RV6A enough to depend on them to do LOP without engine damage.

I'll continue reading but for the time being I think we'll just fly at the usual 24 squared settings that the previous owner and most people I've talked with recommend because nobody I've spoken with has been able to provide an alternate setting that is known for lower fuel burn (even at lower speeds).

Most likely you will never achieve true LOP with your carbed engine, the fuel delivery to each cylinder is too inconsistent. I pull mixture to where rpm is ~10 lower than full rich and that has proved over the past 23 years to be a pretty good economy setting. I assume some of the cylinders are running a little LOP.

But this thread has drifted far away from the original poster's inquiry. ;)
 
Hi Dave. I'm not giving up that easily. This is not rocket science. Infact rocket science and jet engines are likely the reason we lost a lot of this understanding for a generation. People like Lindbergh has this all worked out back in the 20's, then applied it again during WWII.

http://www.charleslindbergh.com/wwii/

I too was trained like you by some of my instructors. Set to 24 square and nervously pull the mixture back to some arbitrary point based on a totally garbage EGT gauge. It was absolute bollox.

Lycoming state that you can basically put the mixture anywhere you like at power settings less than 75% power. Most pilots use 65% as their limit just to give them an additional buffer, and this can be controlled by simply pulling the throttle back to get you to 22" of MP. If you want more margin when you are starting down this path, then take off a couple more inches. To address Sam's comment, with the MP so low, it doesn't even matter if the cylinders are unbalanced because your intake manifold distribution isn't perfect, because the power levels are so low the engine doesn't care if it's rich or lean.
There's a reason we no longer walk around behind cars smelling unburnt fuel fumes anymore. It's because they are running LOP almost entirely, except when they are pulling hard up a hill, ensuring that all that fuel is turned into HP.
I'm sure there's another RV pilot in your area that would be delighted to take you up for a fly and show you LOP operation in the real world. Once you see it run in person, you will realize there's nothing to it.
On the AVGAS side of things, the lead bromide biproduct of combustion is a salt and is the primary contributor to corrosion in aircraft engines. You are doing yourself a disservice running it. There's no fuel at the airport I'm based at, so I just fill drums and have my own rotary drum pump. Not hard, way better for your engine and way significantly cheaper. You can mix mogas with existing AVGAS, with no changes needed.

Tom.
 
I pull mixture to where rpm is ~10 lower than full rich and that has proved over the past 23 years to be a pretty good economy setting.

Did you mean 100 RPM lower or do you actually just tweak the mixture a little bit until the RPM needle nudges down ever so slightly to represent a 10 RPM drop?

But this thread has drifted far away from the original poster's inquiry. ;)
Sorry everyone - I didn't mean to hijack the thread - but really appreciate the input and patience with my being in the early stage of the learning curve!
 
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Hi Dave. I'm not giving up that easily.
Thanks Tom - I appreciate your persistence. I will try your suggestion of setting MP to 22 (should I dial down RPM to 2200 or leave it at 2400?) and then experiment with leaning the mixture while watching the CHT readings.

On the AVGAS side of things, the lead bromide biproduct of combustion is a salt and is the primary contributor to corrosion in aircraft engines. You are doing yourself a disservice running it. ...(using Mogas is) way better for your engine and way significantly cheaper. You can mix mogas with existing AVGAS, with no changes needed.
Good to hear! But I have what may be a stupid question - if my fairly common 180HP Lycoming 0-360 A1A engine can run ethanol free 93 octane Mogas, then why has the transition to a leadfree aviation alternative been such a long drawn out process? Couldn't many engines like mine just have switched to 93 octane Mogas versus waiting for some special lead-free alternative aviation fuel to be developed? What am I missing?
 
Yup it works fine in your engine, I’m sure there is probably an STC for it however it doesn’t work so fine in a higher compression engine:)
 
Hi Dave. The whole unleaded avgas debacle has been because they have been trying to find a one-size-fits-all solution so they only have to use one fuel type per airport. It's been the 20% of aircraft equipped with high compression engines and turbochargers that has held the show up, not the standard compression engines like yours. You could have been running 93AKI mogas for years, and some airports here in Australia have 93AKI on tap for that reason, but they also have to stock 100LL for the rest of the fleet. This has all now been solved with the G100UL, but it's sure been a long ride to get here.

Tom.
 
Thanks Tom - I appreciate your persistence. I will try your suggestion of setting MP to 22 (should I dial down RPM to 2200 or leave it at 2400?) and then experiment with leaning the mixture while watching the CHT readings.


Good to hear! But I have what may be a stupid question - if my fairly common 180HP Lycoming 0-360 A1A engine can run ethanol free 93 octane Mogas, then why has the transition to a leadfree aviation alternative been such a long drawn out process? Couldn't many engines like mine just have switched to 93 octane Mogas versus waiting for some special lead-free alternative aviation fuel to be developed? What am I missing?

You should use the AirPower app mentioned or the Lycoming chart to figure out whatever MP/rpm combination is comfortable (vibration, noise, flicker etc) that gives the desired power setting. For example 22/2400rpm may be 65% power, or 26/1900rpm might also be 65% power, but 1900rpm may be very smooth or very vibraty. Just also note that many props have an rpm range that they recommend not running for a prolonged time at. Many Hartzells it’s 2000rpm - 2250rpm, which means most people ending basically with a few rpm options, but much more flexibility with MAP settings.

MOGAS gas is a whole other discussion. Yes, your engine can easily run it, but that doesn’t mean the overall plane is setup to run it, depending on fuel pump, fuel line routing, and several other things. While I share Tom’s enthusiasm for getting rid of lead in the gas, for most of us, it’s simply not available on any type of XC flying (so you end up burning 100ll anyway), and the hassle and cost of transporting it to the hangar for local flights dampens the benefits. In my area, the cost delta between high octane mogas and 100ll is very small, such that if you have to buy any special equipment for transporting or storing it, it basically becomes the same price as 100ll (the lead free benefits notwithstanding).

If you do want to play with mogas, and you don’t have much experience with it, I suggest you approach it very cautiously, and do test flights in a controlled setting until you verify your plane will work with it. Having fuel issues is no fun.
 
Most likely you will never achieve true LOP with your carbed engine

Sam, with all due respect, this is not entirely true. My ship, sporting dual electronic ignition, and a carb, is easily leaned to where the engine noticeably looses power, well lean of peak. And still runs smoothly. Even more so since I changed to Iridium plugs...
The -8 I occasionally fly has the same engine but injected, and standard mags, but is almost impossible to set LOP.

Electronic ignition is the major factor permitting LOP operation.
 
Sam, with all due respect, this is not entirely true. My ship, sporting dual electronic ignition, and a carb, is easily leaned to where the engine noticeably looses power, well lean of peak. And still runs smoothly. Even more so since I changed to Iridium plugs...
The -8 I occasionally fly has the same engine but injected, and standard mags, but is almost impossible to set LOP.

Electronic ignition is the major factor permitting LOP operation.

I said "most likely" which means it may not be entirely true. :)

But I think as a general rule a carbed engine is not going to achieve the same degree of balanced LOP as one with calibrated injectors.

Glad to see you are pleased with the performance of your engine.
 
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I run my o-360, which has been converted to an IO, at nearer to WOT (wide open throttle) than most here are suggesting.

When it was carbureted I ran 26 inches and just pulled the red knob until the RPM came down to 2350, on the then fixed pitch Sensenich. That gave me around 7.5 GPH with CHT's of 320F or less. Up high, where you can not get 26 inches, I ran WOT; also with good results.

When converted to fuel injection and a CS prop all this has become easier.
The engine has always had one electronic and one magneto for ignition. I am confident EI will ignite a LOP mixture much easier, smoother and further LOP the a magneto.

PS: 14.8 times the fuel flow gives the HP number when LOP.

7.5GPH x 14.8=111HP or about 62% on my 180HP engine.
 
This is what I am getting

Since I was the OP and was challenged to post my own numbers...
Going back to my original question: What are the "real world" numbers for a 150 HP FP RV6-A with regard to max speed? Here is what I got on a speed run lately: Bear in mind, this is an old "slow build" 6A with the old style pants and a 1400 hour engine (with decent compression). Sensenich metal FP prop with the 2600 rpm red-line.

Full throttle
7500 ft.
TAS = 153 kts 176 mph
CHT = 336 F on # 3
EGT = 1295 F on # 4
RPM = 2534
MP = 23.9 in Hg
OAT = 67 F
FF = 11.5 GPM
GS = 178 MPH
 
You caught my eye with RV6-A and 1400 hour engine.

I just sold a similarly old plane with that same old designation on the data plate and almost the same time since new engine.

I did a speed run not too long ago, but did not get all the data points you did.

O320-E2A with 9:1 pistons so per @Mahlon 164hp
Sensenich FP metal prop
Sam James wheel pants
One Slick mag, One PMAG
2550 RPM on the throttle
Leaned to slightly LOP
8500 ft. indicated altitude
Indicated TAS = 160 kts
RPM = 2550
FF = 7.5 GPH
GS = 159.5 kts per four point GPS
 
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Since I was the OP and was challenged to post my own numbers...
Going back to my original question: What are the "real world" numbers for a 150 HP FP RV6-A with regard to max speed? Here is what I got on a speed run lately: Bear in mind, this is an old "slow build" 6A with the old style pants and a 1400 hour engine (with decent compression). Sensenich metal FP prop with the 2600 rpm red-line.

Full throttle
7500 ft.
TAS = 153 kts 176 mph
CHT = 336 F on # 3
EGT = 1295 F on # 4
RPM = 2534
MP = 23.9 in Hg
OAT = 67 F
FF = 11.5 GPM
GS = 178 MPH

For 150 HP, 2534 rpm, and the old wheel pants, this is pretty good. There's a post in here somewhere on how much you can gain upgrading the pants.

Edit: found it https://vansairforce.net/community/showthread.php?t=195468&highlight=pants
3-5 mph
Call it 4 mph, that gets you to 182 mph

Van's published (for 150 HP) is 185 mph at 75% cruise.
 
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