Mad ramblings - VG30 piston specs, compatability and head cc

ForemanNZ · Post by **ForemanNZ** » Sun Mar 04, 2007 8:19 am

Thinking of how to increase the compression ratio in my J30 Maxima while retaining the VG30E engine, and theres no aftermarket pistons for the NA. Can someone confirm these figures for me - its what I could pull off the internet, and I am sure the DE piston dome is not quite spot on!

Common (VG30)
Bore = 87mm
Stroke = 83mm
Pistons = 6

SOHC
Chamber (cc) = 55
Dome = -1
Gasket = 1mm (guestimated)
CR = 8.98

DOHC
Chamber (cc) = 49.5
Dome = 2.7 (measurement taken from 87.5mm JE)
Gasket = 0.9mm (guestimated)
CR = 10.48

Est DOHC piston in SOHC head
CR = 9.49 (excluding any valve clearance mods), so even if the pistons do work, the compression increase is not as much as I had hoped

Going to extremes though, if I shave the head by 1mm (that gives a chamber volume of about 49cc), use a 0.6mm head gasket and use DE pistons, that gives a compression of 10.9:1, not taking into account that if the piston will clear the valves!!! Sounds tempting

djz · Post by **djz** » Sun Mar 04, 2007 12:01 pm

It seems like an awful lot of work to me for probably not much gain, why not try and find a VG33 to put in there? I think 300 extra cc's would make more different than half a compression point, and it should still run on the factory computer.

ForemanNZ · Post by **ForemanNZ** » Sun Mar 04, 2007 6:42 pm

Yeah, had a look at the head combustion chamber, and its a different shape, so DOHC pistons will probably not work anyway. I should just leave it as is ...

mungyz · Post by **mungyz** » Mon Mar 05, 2007 8:17 pm

supercharge it

NOSFEDZ32 · Post by **NOSFEDZ32** » Wed Mar 07, 2007 9:19 pm

you mean VG33E-R......mmmmmmmmm