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Old 09-30-2010, 12:27 AM   #5 (permalink)
Meph
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Join Date: Apr 2008
Location: ontario
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240Z - '73 Datsun 240Z 240Z
90 day: 34.41 mpg (US)
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i was looking at chevys website out of curiosuity of the new new engine specs, there 2.4 and 3.0 run on 87 oct with 11.2:1 (maybe even 11.7:1 if I remember correct). I don't know if thats useful at all but I found it interesting.

In theory your pulling timing because of pre ignition, as the higher compression ratio will burn faster you need to reduce the ignition point to keep the burn at an optimal point in the cycle. following this theory when you reduce timing to compensate for higher compression your not doing anything negative that would reduce power, just keeping it at the optimal point.

The second thing to consider is detention where the fuel self ignites from another source, as u raise the compression the pre ignition temp in the cylinder can raise to a point where it will ignite without a spark. This higher temp is what calls for a higher octane fuel.

hope that is kinda useful info to you
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