What compression on the piston should I run? Im rebuilding my GSR for some turbo action...

JE Pistons (81mm, 81.5mm?)
9.0:1
9.8:1
12.5:1

Im thinkin about goin with 9.8:1 for overall best results (with boost)?

 

81mm bore (stock) 9.8:1 compression ratio (over time the carbon builds up on the piston increasing compression)

 

After having the JE pistons and a set of Endyn pistons in hand I can honestly say the endyn pistons are much better that the JEs. UNless you have some custom JEs made with the features that come standard on the Endyn pistons, I wouldn't bother with the JE pistons. Depending on the rest of your set up 9.5-10.5 is a good place to start. Carbon will not increase compression that much. You may raise the compresson by .01 point. other wise your engine is running too rich.

If the engine is already 81 go ahead and bore it .5mm over to straighten up the cylinder walls and get a good ring seal.

 

OK thx guys I think ill go .5mm over...

I just calculated the parts total ($) on ks-motorsports.com and its gona be over 3k to say the least :/

so after all said and done, with head work, im thinking 4k-ish, but ill have a damn bulletproof engine revving to 10 grand