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UL520T powered RV-8 engine install

chopperchops

Active Member
I hung the 220hp UL Power 520T today on my RV-8 yesterday, so I can start planning where I am going to put everything (and for a visual progress boost!).
To hopefully reduce the potential Vne TAS/IAS debates, I have installed a throttle, am looking at flying as fast as I can while maintaining safe margins, and have been VERY involved in a couple of RV-7 accidents that have involved flutter.
Anyhow, the engine weighs 122kg complete. Obviously with the reduced weight I had to mount it further forward, with a delightful benefit of providing some more space on the firewall.
I have heat shields to protect the engine mount tubes, and a heater muff is on the way. I have opted for dual ECUs, which are mounted in the nose locker away from the engine bay warmth.
Cowls are being developed for the ‘8 at the moment, however I am contemplating modifying a Vans/Sam James/Showplanes cowl.
Plenty to keep me busy for a while!
 

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Nice. We seriously considered that motor in our rv7 during the build. Looking forward to seeing the progress.
 
Rob, May I suggest that you hold your phone sideways when you take all pictures.
It will make the pictures way easier to view.
 
Rob, May I suggest that you hold your phone sideways when you take all pictures.
It will make the pictures way easier to view.

Hahaha, yes I spent a bit of time trying to figure out how to rotate the images!
WILCO, and I’ll update the progress as it unravels (slowly!).
 
Looks great and hope it works just as well.

Noticed the fuel pumps are mounted vertically and pretty high (relative to fuel level). In my research both of those factors are undesirable (for this style pump) and can lead to an early death of the pumps.
 
We have one RV-8 flying the UL520i for a couple of years now (HB-YES), also with a lengthened nose.
Flies regularly, reported excellent performance and reliability last time I talked to the builder.
 
NICE!!!

Regarding that last photo - I presume that's the fuel pumps (in grey) and filters (in red)? Experience from the Subaru crowds is that in order to avoid vapour lock issues, you really don't want to be sucking on fuel, or at least want to limit that as much as possible. That means keeping the fuel pumps as low in the plane as possible, while making sure you have as much free flow to them coming from the tanks as you can.

I am not really familiar with UL engines. Do they have an excess fuel flow and fuel return line, like we have with the Subarus? Our pumps move in the order of 55 GPH each, so any less free flow to them than that will result in lower pressures in the lines leading to them, with all associated vapour lock issues. Mounting them above the fuel tanks will make things worse.

Might be something to discuss with UL, and/or to copy from other implementations?

And the other remark - obviously when mounting the ECUs in your forward locker area, be sure to protect your connectors from shifting luggage occupying that same locker :)

Looking forward to seeing your further progress!!!

Hans
 
Fuel pumps

Thanks Michael and Hans. I must admit I got the idea from another UL installation (not that that makes it correct!). I will go back to the factory for further guidance. I would like to get it correct at this stage of the build.
Thanks for the feedback, and always happy to receive more!
 
Looks clean Rob and should give some sparkling performance. Looking forward to your flight tests.:cool:

As others have mentioned, not best practice to have the pumps mounted like this or on the firewall exposed to heat. These look like Bosch roller vane pumps and they are particularly bad at priming and drawing head, preferring a flooded inlet or at least minimal head.

Not that the UL engines are cheap but they give folks a reasonable alternative to Lycomings which seem to recently have 1-2 prices increases per year.
 
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I've just studied the UL Power installation manual. It doesn't tell much on the topic of fuel pump placement. The advise FWF, but that is about it.

Given that the engine uses the same setup as the Subarus (3 Bar fuel pressure, high excess fuel flow with pressure regulator and return line), it makes sense to study what has been proven to work and what has been proven troublesome with these engines.

One of the recurring themes with the Eggenfellners was vapour lock. Best practice ended up like I mentioned - pumps as close to the tank as possible, as low as possible. Most of us ended up with the pumps and filters on the cockpit floor, in the center of the fuselage. Build a box around it and drain that box, if you're afraid of fuel in the cockpit. Best place by far would be INSIDE the tanks (automotive style), but getting the electric power in is a bit of a thing then. Second best place is on the cockpit floor, close to the tanks, and effectively lower than the fuel level.

You might consider using AN8 fittings upstream of the pump, rather than AN6. 55 GPH per pump is a lot of fuel flow for an AN6 tube, inviting pressure loss which you try to avoid upstream of the pump.

The UL Power manual suggests a setup with coarse pre-pump filters (low pressure drop, however enough filtering to protect your pumps - good practice), then the two pumps (one redundant), ending in ONE post-pump fine filter. I wonder what happens when that fine filter gets clogged? On my setups, I have opted for also TWO fine filters, and only tying the fuel lines together downstream of these. Gives you extra redundancy without much weight or effort.

UL power mentions "If you use a gascolator, then...". In my opinion, there is no place for a gascolator in these setups. Gascolators have never been designed for the fuel flows that we subject them to. And at the same time, due to our pumping round the fuel all the time, we're much less prone to stop an engine when a bit of water is in the tanks. Bottom line: don't use a gascolator.

Next up on my todo list: studying the UL power section on electric system. See what I can learn from that :)

Good luck with your build!!!
 
I've just studied the UL Power installation manual. It doesn't tell much on the topic of fuel pump placement…

Next up on my todo list: studying the UL power section on electric system. See what I can learn from that :)

Good luck with your build!!!

Yeah nothing on pump placement. I will follow the general advice above. I will most likely stick with keeping them on the firewall, however I had always intended to shroud them with a blast cooling duct.

Regarding the wiring, they do provide an installation diagram, however there are a few improvements to be done.

Cheers everyone!
 
...I got the idea from another UL installation (not that that makes it correct!).

Perhaps a high wing?

Find a location inside the fuselage, horizontal, as close to the floor as possible. Avoid right angle and banjo fittings on the suction side of the pumps. Tube ends on flex lines are fine.

Cool project. Looks like it could be a lot of fun.
 
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What Dan said.

90 deg fittings are acceptable downstream of the pumps where the fuel is under pressure. On the floor is the best place, well proven in hundreds of thousands of EFI flight hours on RVs. Have seen a bunch of firewall mounted pumps fail in short order if not done right. The Bosch pumps don't tolerate entrained air for very long. Here are some photos of an RV-8 EFI pump and filter install:
 

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I know I’m just echoing what others have said, but definitely put your pumps as low in the airframe as possible. Pumps are designed to “push” much better than ‘pull”. Also, I’m not sure what brand pumps you have, but you may want to consider high quality Walbro pumps such as those sold by SDS or FlyEFII.
 
I have the Walbro pumps in the SDS fuel module in the Rocket and it is mounted on the floor, just ahead of the spar, and with the inlet end as close to ship CL as I could get it. It was a pain, but this is about as low in an RV style airplane as you can get without going outside the OML. I have zero 90 degree fittings on the suction side (including the ones inside the tanks), run rigid -6 hardline everywhere except the firewall to engine, and (concerning the comment about gascolators not flowing enough) an Andair gascolator used as a pre filter.

I can run gas station car fuel in 115 degree OAT, see almost 30 GPH at takeoff power, and have never had a fuel supply or vapor lock issue.

I'd urge you to take Ross' advice and reconsider the fuel pump scheme. He knows what he's talking about.
 
I've always thought that the UL520iSA (the aerobatic one) would be a great match for the RV-8. I'm not talented enough to do all the fabrication work required to install an engine like that though. An aerobatic C/S prop is the other hurdle. Hopefully the cowling and everything will be available soon with minimal fabrication required!
 
If anyone from Van's is reading this thread.....I and I'm certain many others are hoping Van's takes a careful look at a UL520 option for the RV-15.
 
Has anyone done any testing on how much the forward shift in mass for these lighter engines will affect spin characteristics? Keeping the CG the same should keep the stall angle of attack the same but shifting the mass forward will increase the moment of inertia of the fuselage along the longitudinal axis. This will change the spin rate and angle somewhat, but I am not sure by how much.
 
I've read that moving the prop forward is destabilizing. That's not to say by how much, or whether normal pilots could notice the difference.
 
Has anyone done any testing on how much the forward shift in mass for these lighter engines will affect spin characteristics? Keeping the CG the same should keep the stall angle of attack the same but shifting the mass forward will increase the moment of inertia of the fuselage along the longitudinal axis. This will change the spin rate and angle somewhat, but I am not sure by how much.

I didn't know you could change it.......:rolleyes:
 
I shouldn't type technical questions when trying to pay attention to other things. I should have said stall speed instead of AOA.
 
I've read that moving the prop forward is destabilizing. That's not to say by how much, or whether normal pilots could notice the difference.

On my Jodel (which essentially looks like a fastback RV9 with a funny wing). I've shifted a lot of things around (including moving the pilot seat back by quite a distance), and ended up with the prop some 18 inches farther forward. No destabilizing noticeable at all.

FWIW
 
Has anyone done any testing on how much the forward shift in mass for these lighter engines will affect spin characteristics? Keeping the CG the same should keep the stall angle of attack the same but shifting the mass forward will increase the moment of inertia of the fuselage along the longitudinal axis. This will change the spin rate and angle somewhat, but I am not sure by how much.
I'm quite some time away from flying (just completed RV-8 empennage, wing hopefully delivering next month), but I'm considering one of the 520's on my build and have been in touch with the US team for ULPower. I'm a USAF TPS grad from a previous life and have already started planning the potential stall/spin/departure test program; won't be complete for a few years but if it all works out would be excited to add to the community's knowledge.

FWIW, initial talks with the TPS experts do not expect much adverse impact. The RV's have plenty of rudder and elevator authority!

Chris
 
I'm quite some time away from flying (just completed RV-8 empennage, wing hopefully delivering next month), but I'm considering one of the 520's on my build and have been in touch with the US team for ULPower. I'm a USAF TPS grad from a previous life and have already started planning the potential stall/spin/departure test program; won't be complete for a few years but if it all works out would be excited to add to the community's knowledge.

FWIW, initial talks with the TPS experts do not expect much adverse impact. The RV's have plenty of rudder and elevator authority!

Chris

Your call sign seems awfully familiar. Did you ever work AGCAS at the 416th with SIREN?
 
Good locations for fuel pumps

In the RV-8, there is a very nice location for the fuel pumps on each side of the fuselage, just ahead of the spar (The F-804 bulkhead) and the gear towers. There is already the "mid-cabin brace" there ( think that is what it is called) to provide a convenient partial enclosure for the pumps, and you could easily complete the enclosure with a panel extending from the brace to the floor.

In the "stock" arrangement, the only thing in those bays is on the left, it is where the fuel selector lives. I think there is plenty of room in there.
 
As intriguing as the UL520T seems to be, it does not appear to support a hydraulic constant speed prop? Is that true? If so, really disappointing.

It would still be a great choice for the RV-15 with a fixed pitch prop, but for a good-performing RV-8, with the power available from this engine over this altitude range, it really needs a constant speed prop.
 
MT has electrically actuated props as well

Talking to the prop guys at Osh, electric props are not acceptable for aerobatics. They don't respond fast enough to keep the RPMs under control. That being said, normal props aren't ok for aerobatics either, since if you lose oil pressure they go flat and you overspeed the engine. There's plenty of people doing all sorts of aero with non-counter weighted props though. So this isn't a suggestion either way, just something to keep in mind while considering the electric prop.
 
Plenty of fixed pitched RVs doing aerobatics frequently as well. When using an electric C/S prop, you'll just need to accept that RPM management via throttle is still part of your aerobatic ops.

The Airmaster prop controllers have a 'hold' function. So likely a smart idea to set your aerobatic 'pitch' and leave it (treat it like a FP prop now), do your circuit, then when you're headed home turn it back to C/S cruise mode.
 
I think you just have to get used to the nuances of electric props. I have a number of customers using MT electrics with good success. Russell Sherwood has 1000 hours on his now- 260mph Glasair.

You wouldn't use one for competition aerobatics most likely but they work fine for mild stuff and cross country flying. As mentioned, most have a manual setting which is often used for takeoff and you can toggle in pitch as needed. Switch to auto in cruise.
 
So by using a UL520T, rather than an angle-valve 360, I probably pick up 6 kts. But then I lose 4 kt of that with the slow, thick-bladed MT prop? No thanks.

Now, if Whirl Wind would make blades for the MT electric hub, we might have something.....
 
The UL maintains 220hp to 15,000 feet. Me thinks you'd pick up a lot more than 6 knots at altitude-not that it would be too useful in an RV with the low Vne.

We see the MTs seem to be fairly decent below 2400 rpm on the RV-10s at least. Still seeing over 170 knots up high.

When matching my gearbox, the MT engineers recommended I keep max rpm below 2550 for takeoff since I had a gear ratio choice. They admitted that efficiency took a fair hit at 2700.

I think some folks just want something different from a Lycoming and the UL brings something different to the table. I'm looking forward to seeing how it works.
 
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I think some folks just want something different from a Lycoming and the UL brings something different to the table. I'm looking forward to seeing how it works.

I'm 100% in line with this. The concept is brilliant - a mildly boosted engine that provides better performance up high. AND saves some weight too! (and maybe even a little bit of money?)

I just wish they had gone the final hoop and put a prop governor on it.
 
I'm 100% in line with this. The concept is brilliant - a mildly boosted engine that provides better performance up high. AND saves some weight too! (and maybe even a little bit of money?)

I just wish they had gone the final hoop and put a prop governor on it.

AMEN!!!

Nothing but so-so experiences (at best) with electric props here.
 
When matching my gearbox, the MT engineers recommended I keep max rpm below 2550 for takeoff since I had a gear ratio choice. They admitted that efficiency took a fair hit at 2700.

Interesting....

On my Jodel, when I upped the reduction ratio from 2.12:1 to 2.29:1 (so takeoff prop rpm from 2650 to 2450 and cruise rpm from 1950 to 1800), I picked up 400-500 fpm and needed 2 fewer inches of MAP for the same cruise speed.

On my current setup, running more RPM has the engine producing more power, yet doesn't produce one knot of extra speed. All the extra hp gets consumed by more prop drag.

All of this seems to confirm that the MT really is a low-rpm prop.

NSI used to have an electric prop hub with Whirlwind blades. Proved to be a complete disaster on my application. One hub started to develop a lot of play and the next one made the blades bind at anything over 80 mph.

I love my MT and am putting one on the RV3 as well....
 
I wish MT and perhaps other electric prop makers would speed up the pitch change rate. Curtiss electric props were used on many US bomber and fighter aircraft in WW2. Hundreds of thousands of them. They worked in those extremes of speed.
 
The UL maintains 220hp to 15,000 feet. Me thinks you'd pick up a lot more than 6 knots at altitude-not that it would be too useful in an RV with the low Vne.

We see the MTs seem to be fairly decent below 2400 rpm on the RV-10s at least. Still seeing over 170 knots up high.

When matching my gearbox, the MT engineers recommended I keep max rpm below 2550 for takeoff since I had a gear ratio choice. They admitted that efficiency took a fair hit at 2700.

I think some folks just want something different from a Lycoming and the UL brings something different to the table. I'm looking forward to seeing how it works.

In contrast, testing my Whirl Wind prop at 5000 ft, mixture to peak EGT at each RPM, WOT, I tested from 2300 all the way to 2750, and the airplane went faster with each RPM change. The speed gain at 2750 was small compared to 2700, but it was measurable. On Bob Mills' Rocket-six, the speed gain continues to much higher RPM than that. I probably shouldn't say how high though ;) His WW racing prop was designed with twist optimized for higher advance ratios since the airplanes are going so much faster. The thin tips don't suffer much transonic drag rise, at least up to the speed and RPM we have tested.
 
Now, if Whirl Wind would make blades for the MT electric hub, we might have something.....

When I spoke to Airmaster a couple of yrs ago they told me they use Whirl Wind blades in their electric prop for Lycoming engines, so might be an option for the UL engine. They also quoted a pitch change rate of 4deg/s, I’d be interested to know how that compares to a hydraulic CSU?
 
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When I spoke to Airmaster a couple of yrs ago they told me they use Whirl Wind blades in their electric prop for Lycoming engines, so might be an option for the UL engine. They also quoted a pitch change rate of 4deg/s, I’d be interested to know how that compares to a hydraulic CSU?

A hydraulic C/S prop can go the full pitch range of about 20 degrees in just a fraction of a second.
 
Hey Ross, have you looked at the combustion chamber design on the UL520T? It is a cross-flow head with both spark plugs on the same side (top).

What do you think?
 
Would make sense from a "packaging" perspective. Six cylinders -> smaller bores so design considerations associated the flame speed are less of a factor. Unfortunately, we'll probably never know what design decisions were based on compromise. Waiting on Ross's answer.
 
The plugs are very high on the top side of the chamber. Functional but not ideal in a modern engine design. I don't know what the chamber looks like, couldn't find any photos.

Cross flow head is a good idea for packaging.

Solid, non-roller lifters and rockers seem rather outdated and will require more maintenance hours, increase friction and wear.

We'll just have to see how they perform in service now that they are a bit more mature. They had some piston issues in the beginning and apparently solved those a few years back.
 
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