My friend is swapping in a B20VTEC setup consisting of a JDM 98 B20B block (P3F) and a USDM 98 GSR head. The question comes up, which octane does he have to use? According to C-speed Racing.com (http://www.c-speedracing.com/h...c.php), compression ratio will be at 9.2:1, whereas a stock B20B is at 8.8:1 and requires 87 octane. Would the addition of a GSR head require 91 octane or is compression ratio still low enough to run 87? For reference, stock B16's are at 10.2:1 or something like that, and require 91 octane.

Thanks for the help.

 

i have always used 91 octane on my b20/vtec motors. even on 10lbs of boost. Although i have never had a gsr head. the gsr head does raise the compression ratio a bit. but i have never tried to use anything lower than 91 octane so i am not sure if it will ping on lower grade fuel. But their are some ways to find out if it is pinging/detonating.

 

I wouldnt use anything lower than 93

 

you don't know what you are talking about