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copbait73 copbait73 is offline
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Join Date: Nov 2003
Location: Chesterfield IN
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Originally Posted by NY930 View Post
Hi Walt,
Most people feel that the stock CIS fuel delivery would be lacking with higher performance modifications. That's why I installed a AFR gauge. Even with the 3.5L, new K27, Headers and an aftermarket Intercooler - I'm running 11.0 at wide open throttle under full boost.
Also, after the broken rings and cracked cylinder, my 8 to 1 Mahle pistons looked great and unscathed so the dreaded dentonation was ruled out due to a possible lean fuel delivery condition.
My question is:
Are AFR readings the optimum way to determine if the fuel delivery system is adequate for the additional modifications?
Sorry you are selling your car. It is my personal opinion you have been lead to some very basic wrong conclusions you read here or from your mechanic regarding turbo engines and that these are causing you reliability issues.

A/F in and of itself is not a measure of safety, firing pressure is and there is no gage for this - but there are knock sensors in modern cars. When one goes down the route of increasing the fixed compression ratio from factory 7.0:1 to 8:1 you buy into running lower boost pressure, not higher, if you want to maintain safe firing pressure limits. This is not an issue of CIS vs. EFI, rather limitations of the basic engine configuration your engine was built to.

Octane is the next critical limitation. Today’s pump gas is very limiting and expecting high performance on fuel that is daily becoming worse is another driver toward having your car in the shop vs. ripping up the street. All your performance add-ons just restore some of the safety the factory sold in this car, when you consider today’s inferior fuel. I suggest setting your boost at .8 bar and reactivating the over boost circuitry – this is there to prevent the failure you just experienced.

I feel if you do both you can have your car, enjoy it’s high performance and stay out of the shop.

Last edited by copbait73; 08-16-2011 at 11:07 AM..
Old 08-15-2011, 08:36 AM
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