Morning all I am a car and motorcycle mechanic and built/designed many performance motorcycles and cars. I am in process of building my first aircraft motor (540) and wondering what the difference is going to be compared to what I have learned to aircraft. I'm setting up a stand alone ecm and would prefer to use cop coils and automotive injectors but I would prefer to ask now than find out later that somethings just dont work. I would think a combustion motor is a combustion motor the only issue I have so far is alot of the normal sensors I use do not hold up in a lead condition from 110 LL . Thanks in advance
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Aircraft vs car tune
- Thread starter graffixx
- Start date
glades cat
Well-known member
Sounds like an interesting project. Is the engine going on an airboat? Yea, Oxygen sensors don't like Lead. Exhaust and Cyl temps are important to keep in check and will help you tune the timing and fuel ratio.
Certainly interested in following this build.
Certainly interested in following this build.
Slidin Gator
Well-known member
Aviation 100LL has 4 features that are different from pump gas:
- Lead.
- Higher octane (thanks to the lead).
- A slower burn rate, which is more optimum for the low engine speeds.
- No ethanol
Lead is an easy/cheap way to make octane, but they have left it in aviation fuel almost as a "Just in Case" some old airplane does not have hardened valve seats. Assuming you have hardened valve seats, which you should, your engine does not need the lead, just sufficient octane for your tune, compression, temps etc.
Ethanol is strictly an issue for older fuel components that are not rated. Given your plans your fuel system should be made for Ethanol such that Ethanol provides a much simpler route to higher Octane. Also note that Ethanol burns slower and cooler than pump gas.
You should be looking into E-85 as your fuel of choice for this build. You should be able to tune for 93 pump gas, E-85 and AV gas (if you solve the lead issue). E-85 will be your best choice for making big power.
- Lead.
- Higher octane (thanks to the lead).
- A slower burn rate, which is more optimum for the low engine speeds.
- No ethanol
Lead is an easy/cheap way to make octane, but they have left it in aviation fuel almost as a "Just in Case" some old airplane does not have hardened valve seats. Assuming you have hardened valve seats, which you should, your engine does not need the lead, just sufficient octane for your tune, compression, temps etc.
Ethanol is strictly an issue for older fuel components that are not rated. Given your plans your fuel system should be made for Ethanol such that Ethanol provides a much simpler route to higher Octane. Also note that Ethanol burns slower and cooler than pump gas.
You should be looking into E-85 as your fuel of choice for this build. You should be able to tune for 93 pump gas, E-85 and AV gas (if you solve the lead issue). E-85 will be your best choice for making big power.
glades cat
Well-known member
If you want to run pump gas, you need to lower the compression ratio, and as a result, will make less power. AVGas is an Alkane reformate fuel. It doesn't have Oxygenated nor Aromatic Hydrocarbons. Notice, it doesn't have the perfume smell that MoGas has. It is a better fuel, will burn cleaner, slower and not detonate under the high temps and compression of air-cooled cyls. AV engines don't have knock sensors to cut timing.
Bottom line...if you want to make power and have more than 8.5-9:1 compression, use AVGas.
If you want to use MoGas, put 7:1 Pistons in it.
Bottom line...if you want to make power and have more than 8.5-9:1 compression, use AVGas.
If you want to use MoGas, put 7:1 Pistons in it.
The compression ratio on this engine is 7.3:1. I can tune it much better with o2 sensors.not sure how an av engine would handle knock sensor but I will find out. I'm pretty sure the gear box will produce false readings. I have a car motor running 33lbs boost with 93 octane mogas producing over 3 hp per cubic inch. Not saying that is safe but it is my daily driver.
Slidin Gator said:
The engine already makes great power I just dont care for the mags and mechanical injection. Factory specs are 450 max hp at 975 torque @ 8lbs boost it is turned up to 12 lbs now with a better turbo/wastegat/blow off but I would feel much better knowing what is going on and being able to control it. And obviously fuel economy is hideous lol