91 octane highest compression ratio?
Thread Starter
On The Tree
Joined: May 2004
Posts: 101
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From: Littleton, CO
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?
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.
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.
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.
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.
Launching!
Joined: Jan 2004
Posts: 273
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From: Trois-Rivières (Québec / Canada)
Originally Posted by SSpeedracer
Colorado is like 1000 miles above sea level right
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Eric D.
99 Firehawk M6
