Quote:
Originally Posted by Gaz64
Lads, overlap has nothing to do with compression pressure while cranking.
The valve event that influences cranking pressure is inlet valve closing point.
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Yep, "overlap" gives you that pleasant "rumpety, rump" sound, but cranking compression really gets going when the intake valve is closed. Here's a graph of my cam. You can see on the compression stroke that my intake valve is still hanging open (the blue line) a good half way down on the the piston's travel. If my IV closed sooner, my cranking compression (and dynamic compression ratio) would be greater.
