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RarlyL8 RarlyL8 is offline
Crotchety Old Bastard
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Join Date: Jan 2000
Location: Huntsville, AL
Posts: 13,563
Bryan, I think you may be confusing AFR and octane rating. As Don states you can't put the fire out by drowning with gasoline, unless it is the right formula of gasoline. Many factors go into the source and treshold of detonation and octane is but one method to increase that threshold. Our 2 valve air cooled engines are a long way from optimal when it comes to controlling the combustion environment.

Matt, the stock boost level on a 7.0:1 930 engine was ~0.75bar. I wouldn't go above that with 8:1 given all other things equal. You need a margin of safety for all the varied operating conditions your engine will see (as in the above paragraph). Higher octane fuel, large intercoolers, etc will put off detonation of course and allow you to safely run more boost.
Matching a turbo to a high compression high reving engine is a challenge. You need a turbo that will boost well below 0.8bar at 6000rpm while flowing the required air for your displacement. Marty (Copbait73) is a turbo expert and can help you with this.
RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 03-22-2010, 07:38 PM
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