Re: Compression ratio and octane rating

Posted by buickanddeere on March 27, 2007 at 20:25:02 from (209.240.125.126):

In Reply to: Compression ratio and octane rating posted by hogman_2002 on March 26, 2007 at 10:32:44:

Depending on the cam grind and the design of the ports/manifolds etc. A 7.5 to 1 engine may knock on 87 octane and a 9.5 to 1 engine may run fine on the same 87 octane.
Detonation depends on cylinder pressure, rate of compression(piston speed), air/fuel ratio, combustion chamber design/shape, cylinder size, air temp, engine temp & cam timing.
Retarding the timing on a high comp engine just make them loose HP/fuel efficiency and tend to over heat.
Odds are 87 octane will reduce engine power and efficiency.
If your ears can hear detonation, it's already too late to retard the timing.

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