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91 octane highest compression ratio?

Old Jul 10, 2004 | 01:13 AM
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Default 91 octane highest compression ratio?

What is the highest compression ratio that you can safely run on 91 octane gas because that is the highest i can get my hands on out here in colorado?
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Old Jul 10, 2004 | 02:56 AM
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I run 11.2 with 28 degrees of timing with cali 91. I would stick around 11.5 or lower, and go with a thinner head gasket to reduce quench. You will need to tune it to cancel any knock. Detonation killed my last 11.8-1 346ci.
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Old Jul 10, 2004 | 06:10 PM
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Yeah I would say 11.5:1 is the most you could get away with on 91 with max timing, that's what my heads/cam setup was and it ran fine on CA 91 octane. A lower lsa cam and colder plugs will help too will help bleed off some compression too. Good luck.
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Old Jul 11, 2004 | 12:33 AM
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Colorado is like 1000 miles above sea level right

Your mass flow efficiency will be less than Cali so I would guess that you could get away with more compression than an equivalent car in CA. Isnt this one of the reasons you have 91 in CO?

I say go with a supercharger! That would be huge where you live.
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Old Jul 11, 2004 | 10:54 AM
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Originally Posted by SSpeedracer
Colorado is like 1000 miles above sea level right
Hmm... blower will do nothing for his car at that altitude, I would invest in solar panels instead.

--

Eric D.
99 Firehawk M6
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Old Jul 12, 2004 | 12:20 PM
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I was thinking blower cuz thats the only way to do it up here but not enough $$$
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Old Jul 12, 2004 | 12:44 PM
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you would need a high psi one too, or else it would only make it run like you were at 500 miles above sea level
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