Originally Posted by
matt5112
CR is a significant factor in how much boost you can run, but so is your dynamic compression ratio.
So your cam (which has no known specs thus its impossible to calculate DCR), bore, stroke, rod length all help determine DCR.
Simple way of looking at it is, cam lowers it, boost raises it.
So look at what boost levels others running the XPZ use.
Al heads wont matter in this equation because any increased compression you can run will already be imposed by their smaller combustion chamber.
Might want to consider having an experienced machinist work your heads over a little, IIRC there is still room for improvement.
As for timing, you need your peak pressure at a certain point.
IIRC, you typically want 14-16 ATDC for most motors. Unsure on value for our motors.
That depends on your combustion chamber design and a few other details.
AFR and timing are closely related though.
Richer you run, slower fuel burns, more timing you need to achieve same peak pressure point.
12-29-2011
