# most concerning LS3 conversion issues?

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#### skydawg

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

Thanks

#### rv6ejguy

##### Well-Known Member
What redrive/ prop and ECU are you considering?

#### dcstrng

##### Well-Known Member
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

##### Well-Known Member
HBA Supporter
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

##### Well-Known Member
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

##### Well-Known Member
HBA Supporter
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

##### Well-Known Member
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

##### Well-Known Member
HBA Supporter
Log Member
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

##### Super Moderator
Staff member
Log Member
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

##### Well-Known Member
HBA Supporter
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.

#### pfarber

##### Well-Known Member
HBA Supporter
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

##### Well-Known Member
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.

#### slociviccoupe

##### Well-Known Member
Not sure on the ls3 but be carefull of the stock dod lifters. I know they fail often.