Auto Engine Conversion Gearbox for Experimental Aircraft - RV-10

Amazing. About damm time GA engines enter the 21st century

Ben, there are a lot of opinions all over the internet, including here, that think the radiators and coolant must make the LS3 engine heavier. In fact if you unbolt everything from the firewall for the IO-540 and one with an LS3 with the same propeller and fully wet our installations typically weigh 2-3 pounds less with a smaller alternator and light weight starter. We have weighed both for the RV-10. Using the stock alternator and starter will add 5 to 6 pounds, but we like to go with the lighter parts. Many people think that the radiators add a lot of drag too. But the inlet area of our scoops is slightly less than the area of the inlets on either side of the spinner that we eliminate. The scoops moved to the side of the cowling is more efficient due to being further out on the propeller blades where they blow a lot more air into them, especially on the ground. The exit area is larger than the inlet area to create low pressure that helps to pull the air through the radiators as well. The fixed cowling exit shown in the video aft of the nose gear strut has been replaced with an adjustable cowl flap that works the same as the one on a P-51 belly scoop. We hope testing will prove that this will reduce the overall drag further. We are already faster than an IO-540 and burn 30% less fuel at the same power setting, but saving more on fuel costs is always a good thing to have.

That depends on what you want to compare to. The LS3 as we install it puts out 375 HP at our 4500 rpm limit. So for take-off through cruise settings the fuel burns are; 4500 rpm 100% - 375 HP = 22.5 gph 3700 rpm 75% - 283 HP = 17.0 gph 3400 rpm 65% - 247 HP = 14.8 gph 3000 rpm 55% - 210 HP = 12.6 gph None of those power settings compares to the IO-540D that it replaces. A bigger engine puts out higher horsepower and consumes more fuel, even with water cooling allowing for 20 to 30% lower gph/HP. The closest that we can get to a similar power setting for the IO-540D is: 2700 rpm 100% - 260 HP = 19.9 gph compares to on the LS3 at 3500 rpm 69% - 258.6 HP = 15.5 gph, or 22% less 2340 rpm 75% - 195 HP = 14.3 gph compares to on the LS3 at 2800 rpm 69% - 194.2 HP = 11.3 gph, or 21% less All of these numbers are based on dyno data corrected for standard sea level conditions. Actual rpm and MAP settings will vary the performance and fuel flows. The physics of density altitude that effect engine performance is the same for all engines.

That is a good question that no one has asked on this platform before and worthy of a full explanation. This explanation will be for a true certification, not a temporary certification under Experimental Exhibition or Experimental Test that other people have been done recently. Yes, the LS3 could be certified, but it's not practical. It would cost 2 to 3 million and take 2 to 4 years. The certification process requires a lot of paperwork, approvals, and testing. That process will eventually destroy 4 to 6 engines to learn how long they last and how they fail under several conditions like lack of oil, low pressure, abusive uses, loss of coolant, etc. Each failure mode requires it's own engine and the results might require repeating the test with another engine. The worst part is the certification would be good for only that specific version of the LS3. As soon as GM "upgrades" anything or substitutes/replaces any part from another supplier (GM tracks this by issuing a new part number for the same engine with the different parts) the original FAA certification is voided. History has shown that GM changes the part number for the base LS3 about every 10 to 16 months, so the version of the engines you started testing with will be outdated before you finish. It is possible to get a modification to the certification by proving to the FAA that the new part(s) are equivalent or better than the old part(s) making the new part number engine compliant with the certification. Again, more money and time, the possibility of having to repeat some or all of the testing, plus a risk that it will be rejected. The only way to improve on that situation is to invest a few million more and warehouse (more money) as many of the current version of the engine as you can get in the beginning. The risk there is if testing proves that any modifications are required then all of the engines in the warehouse will also need to be modified exactly the same way. But when the supply of those engines run out you have to start over, or file for a modification to the original certification and refill the warehouse. It tends to become a bottomless rabbit hole to throw money and time into. The only way around the central issue of not being in control of the engine configuration is to manufacture the engines under license, if GM will let you do that. Either way you end up with an certified engine that costs as much or more than a Lycoming IO-540 or Continental IO-550, and that is an even tougher selling point to overcome. To me this is not a good way to promote aviation. In recent aviation history over the past 30 years there have been three companies that invested all the money and effort to certify different auto engines. All three went bankrupt in less than 7 years. This company, under two owners and two names, has survived over 22 years without certifying anything, so we don't feel any need to change that. But if you are rich and in need of a huge tax deduction call me. :) Thanks for asking.

The main conversion for an LS3 engine to do unlimited aerobatics is changing it to a dry sump oil system with 5 pickup points. That is not required to do "Gentleman" type aerobatics without negative G's. The only issue you might have without a dry sump oil system is with a bad PCV valve allowing too much oil into the intake. Replacing the $5 PCV valve during annual inspections will prevent that from developing. The difficult part of using any diesel engine for the gearbox and the propeller is how the explosive combustion cycle pulses are dealt with. The combustion cycle pulses on a gas engine is a much slower burn. The older mechanically injected diesel combustion cycle is an instantaneous explosion. This causes the loads on the gears, bearings, shafts, propeller hub, and propeller blades to increase by 12+ times. The modern electronic diesel injection systems will pulse the fuel 10 times during each combustion cycle to dampen the power into more of a sin wave instead of one massive pulse. That helps a lot but the loads form the power pulses are still 3+ times that of a gas engine. That is a big improvement but still requires structural upgrades to everything. This is why certified aircraft diesel engines have a 500-1000 hour TBR instead of a 2000 hour TBO. The weight that you quoted for the R2.8 engine is 20-24 pounds heavier than an LS3. To that you have to add a heavier duty gearbox and propeller. I can't estimate the weight increase for the propeller, but the last time I studied this issue the gearbox would go up at least 45-50 pounds. Adding 65-74 pounds to the engine installation makes any aircraft too nose heavy.

Loved it! Starts to let me think building an rv10 could be in my budget one day. Keep the YouTube updates coming. Awesome work!

Martin, Thanks for your enthusiasm. If you can drop in for a visit and we will take you up for a ride that you will always remember. The side scoops are to get better airflow than what is available with the stock openings next to the spinner (closed off), especially while taxiing. We have never had an over heating problem on the ground no matter how long ground control makes you wait. The side scoops stick out far enough to allow for the boundary layer looses next to the skin. The new inlet area is roughly the same as the old inlet area. The pressure drop across the radiator core is achieved with an exit flap at the bottom of the firewall (behind the nose gear) that is at least 150% larger than the inlet area. The larger exit area also accounts for the expanded volume of air after absorbing heat from the radiators as well as creating a slight vacuum drop. After this video was made we replace the fixed exit area flap with an adjustable cowl flap to do more testing for ground versus flight cooling requirements. Our hope is to reduce drag in flight without sacrificing cooling on the ground, assuming the difference is big enough to measure.

Turbo normalizing to 15,000 feet is already available. With sea level engine performance and less drag cruise speed will increase dramatically. The biggest issue with turbo charging to 700 hp is the torque goes up to 1300 lb-ft. That would be like putting a PT-6 in these small air frames. That would twist them up like an empty soda can. But wait, there are weirder things than that coming by this time next year with bigger engines on bigger air frames that can handle the power.

Tett, the weight of an IO-540 installation and our LS3 installation are virtually identical. I found that the internet is full of miss-leading weight information. This is due mainly to the fact no one gives the details of what their weight includes. Is it just the engine, did they include all of the accessories, wet or dry? Because of that I now own several types and styles of scales to get my own actual weights. Both installations including everything between the firewall and propeller weighing within +/-5 lbs of each other. That includes all fluids and mounting frames for both installations. If we downsize the alternator from 150 amps to 100 amps and use a light weight high torque aftermarket starter we can get down to 5 lbs less. The need for a three bladed propeller to handle going from 260 hp to 370 hp is the only and by far the biggest weight issue. That is why you see an MT composite propeller on this RV-10.

Add a big boy turbo and a built blick with upgraded internals to last and you got a 700 hp that will last you for a very long time, only thing that would need replacing is tranny and turbo after a while

You got a cool looking airplane, and it sounds sweet. Perhaps some FlowMasters to make it super sweet. Nice job.

Bob, with out a doubt there are better ways of setting up the throttle and propeller governor linkages than what the original builder installed. The 18 months since we bought the airplane has been filled with making updates like that. Thanks for the suggestion on the propeller governor linkage.

I'd really like to see you guys offer a custom cowling with a rounded nose and NACA ducts. The blocked-off cowling looks really clunky.

Awesome aircraft ✈️ with impressive engine

It was a little hard to hear but the engine did sound pretty good flying by.

I have an ls1 In my rv7. Currently trying to optimize it. Thank you for the info

My only real concern with that setup is the ECU used. I've seen more than a few Atomic ECUs crap out real early, and most went out while driving. Hopefully you have better luck than they did.

That is so cool

I would like to see some of the new modern turbocharged V6 engines that are in production in aircraft makes sense to use the turbo charging already engineered by auto manufactures. LS3 is a great engine and it could be turbocharged but the don't need the 2 extra cylinders more then enough power with a V6. The big benefit of the LS3 is the aftermarket support lots of it and parts are low cost. GM current turbo engine is the 2.7L V6 L3B puts out 310 HP. The direct injection issues can be mitigated by just dumping the crank case fumes to outside instead of sucking it back into the intake. I also see the issue of sourcing these engines auto manufactures probably don't want anything to do with supplying new crate engines for aviation I could see why the LS series is easy to get.

At 1:21 the way that prop governor lever extension loads the lever and input shaft in bending is downright scary. You'd be much better off using a walking beam bellcrank like Van's does for the RV-8 IO360 mixture.