Engine choice question

[Charles in SC]

I am studying my engine choices for a 180 hp injected. Of the popular engine builders do any of them do better on auto gas or the avgas of the future whatever that may be? Has any of the engine builders tried to plan for this?
Thanks!

 

[Geico266]

Typically, piston compression of 8.5-1 or lower allows the use of mogas.

 

[terrye]

Engine Choice Question

I have some Lycoming Specification Sheets for several engines showing the certified fuels
Model Compression Ratio Horsepower Fuel Grade
O-320 7.00:1 150 80/87
O-320 8.50:1 160 91/96
O-360 8.50:1 180 100 or 100LL

Now granted, neither 80/87 or 91/96 fuels are easily available anymore and it is not clear if the 0-360 specification is a parallel or angle valve version. All have the same bore of 5.125"

I believe the "future" avgas will be at least 91 octane and probably based on premium mogas. I will be building my IO-320 for my RV-9A with 8.50:1 compression ratio based on this assumption. If in 20 years all that's available is 80 grade I'll change to 7:00:1 pistons.