I'm a bit confused about honda compression calculators.. I was checking some aftermarket pistons for my b18c type r and input the specs of the pistons into the calculator and the results came out wrong. Example the aftermarket piston had a 8cc dome, 30mm comp height and it should be 12.5:1 cr. But on the calculator it was only 11.8:1. I used zealautowerks calculator and the honda compression calculator app from my android phone both showed 11.8:1. So which is actually correct? Thanks

 

they're general estimates. if you want to find out what your actual compression is do the measurements yourself and do some math.

 

The difference is the deck height between the GSR and LS blocks. The LS is actually a bit shorter, meaning it manages a bit more compression. That combo will produce 11.8:1 on a GSR block but 12.6:1 on an LS block, both figured with a GSR head.