And for more on that, GPASC says that for maximum engine life, the max should be 8 to 1 on the 2180 and 8.5 to 1 on the 1835.
I agree with the evidence presented that in standard installations the max compression should be 8 to 1 with turbo. 94 octane fuel used to be available from Amoco as their premium fuel. I have not bought it in a while so not sure if it is still available. You can use higher compression ratios with turbo or supercharger (like a belt driven one, a Legacy was featured in Sport Aviation with a belt kit), but it usually requires an intercooler to reduce the heat introduced at the impeller during the pressurizing or "squeezing" process. The reason alot of kits now can be used with higher ratios is that they are being added to multi-port fuel injection units with computer monitored detonation through knock sensors, and alot are sold with intercoolers. Just adding a turbo to an engine by itself will allow a small benefit because the engine will begin making more power without an adjustment in the prop to use that power, or the prop is adjusted to use it, and the engine losing the turbo will be way overloaded with pitch when the turbo does not function. HOWEVER, these are generalizations, and there are more combinations of props engines, and turbos than can be discussed here (I think). My personal opinion is to decide whether the engine will be full time turbo, and adjust the entire setup, or no turbo... Colin Rainey brokerpi...@bellsouth.net
