Anyone know what compression ratios of LS/VTEC motors are? I know Si and GSR heads have different CR's, so I'd assume that the CR on LS/VTECs are different with Si and GSR heads.

Basically I need to know the CR of a LS/VTEC w/GSR head, and CR of LS/VTEC on Si head, both with stock pistions. Also need to know the CR of the stock LS motor (1995 B18B1).

 

depending on head dome volume a little higher, wait for someone else to do the math, you should check in at about stock 9.2:1 or 0.1-2 ponts higher.

 

'99 B16A Si head with '95 B18B1 LS block, 8.5:1 compression pistons. What CR would that yield?

 

hmmm, sorta sounds like you dont know much about ls motor... a standard LS motor has 9.2:1 compression...

as SI head is .2 lower than a GSR head... meaning that a gsr head will yield a higher compression ratio than SI head due to the size of the port opening...

A LS/VTEC motor with stock pistons would be in the high 9's er very low 10's... most people that run ls/VTEC use b16 pistons and that yields a CR of around 11...

If you are running the 8.5 compression pistons... figure about a CR of 9.0:1... can always put a guage in the head to measure it...


just boost it till 20 psi so you can hit the 11.0...