Effect of compression on tune?
12-20-2011, 09:03 PM
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Effect of compression on tune? My car was previously street and dyno tuned, and I am in the process of freshening it up. Engine is a 4.005 lq4, it has zero deck height, -4 cc dish mahle pistons and 64 cc chamber trickflows. The engine previously had a .052 head gasket which gave it about a 10.2 compression ratio. How much of a compression change can I make without needing to get it retuned? I was looking at about 10.8 with a .041 head gasket but I was just wondering. Thanks
12-23-2011, 02:13 PM
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Compression ratio is also your "evacuation ratio" (how
well you toss the spent gas to make room for the new
charge) and it directly affects VE. You indicate a 6%
CR change, and could expect the mixture to change
similarly and toward the lean / ping side. Along with
this you have the higher CR affecting burn speed by
both simple pressure, and charge quality (less spent
residue) meaning you will dial back the timing.
well you toss the spent gas to make room for the new
charge) and it directly affects VE. You indicate a 6%
CR change, and could expect the mixture to change
similarly and toward the lean / ping side. Along with
this you have the higher CR affecting burn speed by
both simple pressure, and charge quality (less spent
residue) meaning you will dial back the timing.
