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most concerning LS3 conversion issues?

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skydawg

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working on a LS3 conversion and wanted to solicit any input/notable concerns/suggestions that might reduce the learning curve.

Thanks
 

dcstrng

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working on a LS3 conversion and wanted to solicit any input/notable concerns/suggestions that might reduce the learning curve.

Thanks
You might scout around for notes on Ben Haas' STOL CH 801 -- Ford power, but was a pretty well-known conversion -- haven't heard much about it recently, but there used to be YouTube clips as well...
 

Kyle Boatright

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You might scout around for notes on Ben Haas' STOL CH 801 -- Ford power, but was a pretty well-known conversion -- haven't heard much about it recently, but there used to be YouTube clips as well...
Unfortunately, Ben passed away a couple of years ago, so much of the information on his successful conversion is gone.
 

skydawg

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Using GM ECM and looking at different PSRU's. Looking more at any LS3 engine block issues, such as if a oil catch may be needed as engine will be under a constant load with a prop. Also, any feed back about adding about 1 qrt extra oil to help maintain enough oil in pan during to prevent pump cavitation during uncoordinated flight as its a wet sump system.
 

Voidhawk9

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Use caution with a GM ECU. It is OK for a car ECU to make you 'limp home', but it may kill you in an aircraft. There are several other options out there that may be better suited, at least one made specifically with aviation use in mind (SDS)!
 

rv6ejguy

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Using GM ECM and looking at different PSRU's. Looking more at any LS3 engine block issues, such as if a oil catch may be needed as engine will be under a constant load with a prop. Also, any feed back about adding about 1 qrt extra oil to help maintain enough oil in pan during to prevent pump cavitation during uncoordinated flight as its a wet sump system.
No need for the catch can or extra oil. The engine was designed to operate at high power settings by GM. No issues with wet sump systems in aircraft unless you're pulling negative G. The folks I know running these in aircraft have had no issues with the oiling or crankcase ventilation systems.

Watch a few things on the GM ECU. Specifically, exceeding coolant temperature limits and what it does does in the case of certain sensor failures to protect the engine. The engine won't develop enough power to get you back to an airport. There have been a few accidents as a result. The ECU also relies on the O2 sensors which don't play well with 100LL if you plan to run that fuel primarily. Closed loop threshold limits may result in fairly high fuel consumption at medium cruise power settings if that's an important consideration for you.
 

Toobuilder

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Id suggest you look at all the info about th P-85 aircraft discussed on this forum. It's powered by an LS based engine.
 

wsimpso1

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working on a LS3 conversion and wanted to solicit any input/notable concerns/suggestions that might reduce the learning curve.

Thanks
My biggest worry with any conversion of an automotive engine to turning a prop is PSRU and ECU. They both have to be rock solid reliable. The engines themselves are pretty terrific.

PSRU's that work for the LS engines seem to be available from several sources. Big issue is how many are operating, how many hours does the fleet have, and how many have failed in use? If a lot of LS engines have been turning a lot of props for a lot of hours and none are breaking, you probably will have a good result too. Sorry, you have to do your own research. If you are running either fixed pitch or electric constant speed, the airboat guys deserve a look or three. Running a hydraulic prop? A smaller set of PSRU will run them.

Carrying over the car ECU looks like asking for trouble to this powertrain engineer. The car ECU runs and monitors the engine, the automatic transmission, the cooling for both, the AC, the power steering, the door locks, the list goes on and on. Way too many sensors with way too many sets of wires and way too much failure mode management programming that you are trying to fit in with. If everything is not working, the ECU backs out the power, and you are doing a forced landing...

My view is that a dedicated airplane ECU is a wise bet. You still get EFI and EI, with trimmed down set of circuitry, easy starts and reliable firing of even horribly fouled plugs, and you can map the engine using Exhaust Gas Oxygen sensors and tune the fuel flows accordingly, then plug those ports and eliminate some more failure modes. An ECU with some failure mode catching is probably a good thing too. And again, how many props are turning for how many hours and how many have acted up in the field are good questions to have the answers for...

Billski
 

pfarber

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You can convert to a carb and use any off the shelf electronic distributor.

You won't lose much if you go back to a cab as long as you get a good intake but the higher profile might be hard to fit under the cowl.

The bigger issue of LS3s would be a PSRU to absorb all that HP/Torque. Most 500hp+ PRSU's are well over $10k.

If you drop down to an LS1 motor and run it at 350-400hp you can use airboat PRSUs much cheaper.
 

rv6ejguy

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The Ballistic airboat drives have no issue with the full 430hp an LS3 puts out. The P85 used this drive successfully. No easy way to put a hydraulic C/S prop on it though so you'd have to go FP or electric.

The LS1 is pretty old now, the LS3 has plenty of improvements, same weight and a lot more power.
 

Toobuilder

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You can convert to a carb and use any off the shelf electronic distributor...
The LS series does not use a distributor; they feature coil near plug architecture. The brain boxes for this are available, but their suitability for aviation applications needs to be explored.

if you want to go away from EFI, then the Bendix based mechanical FI system is a fairly easy retrofit. I've done the mechanical integration on a 5.3 mule engine, but never ran the thing. A carb can pretty much guarantee that you are going to have mixture distribution issues. At least the Bendix retains dry flow in the intake and the nozzles can be tuned to optimize cruise settings.

But with all that work ahead of you, why not just buy the SDS unit in the first place? Tuning takes place with a few keystrokes, it has no hidden "limp home mode" surprises lurking in the code, and it has aviation specific features designed in from the start.
 
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TXFlyGuy

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The Titan / Autoflight New Zealand gear box is well tested on the LS3. Two versions available. One for 600 hp, the other one for 300 hp. But they are pricey.

If you do not need a CS hydraulic prop, then the air boat PSRU's would work fine, and save you some $$$.
 

pfarber

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Aftermarket ECUs get rid of most of the car-centric issues (limp home, security) and as a bonus don't need expensive factory tools to program.

Most will run fine once sensors connected and minimal config. About $800-1500 for a stand alone ECU
 

skydawg

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update. Got almost 200 hrs on c172 test aircraft with our V8. Had a lot of engineering issues that took a lot longer to work through than thought, and ended up beyond our in-house engineering skill set. Had many issues trying to adapt a car ECM and meeting part 33 cert levels, as well as trying to get 2 ECMs to share same system for redundancy. ended up working with same engineering firm GM used to develop true redundant EFI system to get it figured out..... expensive among other things. Working of better prop designs now.
 
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