Originally Posted by vqman 
that said, when you take the forumula for calculating compression ratio, and assume all other things being equal..
b= cylinder bore (diameter)
s= piston stroke length
V_c = clearance volume
Yeah, you're absolutely right. I wasn't trying to disagree, I was just saying that the engineers who design aftermarket pistons take that into consideration and produce them to provide a set compression ratio for that bore size. So when you go with a larger bore, you can keep the same comp ratio, or switch to something different.
Originally Posted by boostednx Ok yes it does flow hold and compress more air but say if i was to take a stock ve 86x86 motor wich i believe is 11:1 compression bored it to a 87x86 and added a set of turbo 8.5:1 compression pistons then i would have bored it and it now has lower compression. I am just saying it doesnt always happen to increase compression .
Originally Posted by vqman when you change to lower compression pistons, you'll definately lose compression.. with going to 87 bore and a much lower compression piston (8.5) i'm guessing you wouldn't be any higher than 9.0:1 or something around there.. maybe 8.75:1
I don't know how much the clearance volume is to do that forumula and know for sure.
When you mix and match, you'll run into the math part. DE 8.5:1 pistons give you 8.5:1 in a DE motor, but if you're using them with a VE head you have a different volume in the combustion chamber, so it throws off the compression.
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