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1. 08:49 PM - Re: Auto Engine - compression ratio vs. octane (DEAN PSIROPOULOS)
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| Subject: | Auto Engine - compression ratio vs. octane |
The big automotive engines of the 1960s took compression ratios to their
ultimate state of the art with premium leaded auto gas. Ratios from 10.5 to
11.5 to 1 were common place with 100 octane auto fuel. Since the unleaded
mandate, computer analysis has advanced the state of the art in combustion
chamber technology so that 9.5 to 1 ratios are possible on regular unleaded
fuel (87 octane) without detonation. If you use computerized engine control
with knock sensing you could probably go even higher. And with avgas being
the equivalent of somewhere around 110 octane autofuel, the sky should be
the limit (not quite but it would be an interesting exercise to see how high
one could go using a modern auto engine with avgas).
Dean Psiropoulos
RV-6A N197DM
Struggling with erratic idle on 0-360
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