compression ratio from tri metal head gaskets?

[Gixxer Squid]

Just found out that my turbo'd z has a compression ratio of 9.5 to 1 which is pretty high in my opinion, however, it has a stock head gasket.

 

I know they are still back ordered but what would be the approximately decrease in compression ratio by adding a 1mm or 2mm head gasket once they become availlable in this millenium if possible? I did a search but could not find the data.

 

Would I have to make other mods/adjustments when putting this head gasket in or just remove the old and in the new, bolt her up and go !!!

 

J

[Pyro]

stock gasket is 1.25mm

 

if you have 9.5:1 cr now then cr will go up to 9.8:1 with a 1mm gasket and drop to 8.9:1 with a 2mm.

 

 

what is your current combo? block, pistons, head, cam, turbo???

[Gixxer Squid]

stock gasket is 1.25mm

 

if you have 9.5:1 cr now then cr will go up to 9.8:1 with a 1mm gasket and drop to 8.9:1 with a 2mm.

 

 

what is your current combo? block, pistons, head, cam, turbo???

 

gt 30 turbo, p90 head, f54 block JE pistons. Car was built for 6000 altitude, hence the higher compression but now I am at sea level.

 

Looks like I need a 2mm whenever they become available.

 

James

[blue72]

I'm interested to know how your motor's built. Perhaps you have some combination of shaving and shimming the P90 and maybe your forged pistons are flat tops combined with the standard head gasket? That I suppose could get you in the 9.5:1 ballpark. I can't think of many other ways to make that happen though (aside from welding up the chambers more or custom domes on the pistons?)

Just curious.

[Daeron]

How did you "find out" the compression of the motor?? Compression check, corrected for barometric pressure, then reverse calculated? Asked the builder? To get a 9.5:1 compression ratio on the ozdat calculator, I had to set up a P90/F54 combo with a ~7cc DOME piston, or a subtraction of about 7cc from the combustion chamber. My understanding with the "P90 0.080 shave" is that you wind up with about a 42cc chamber rather than a 53, so it isn't the standard 80 thou shave job..

 

Could you be mistaken, and be at 8.5:1? That is a standard P90 with flattops...

 

http://www.ozdat.com/ozdatonline/enginedesign/

[Pyro]

also, a cam with longer duration will help reduce cylinder pressure. thus allowing more cr with your setup.

[Gixxer Squid]

I bought this car already built and the previous owner had 4 different people working on the car and such. I finally talked to the mechanic that put it all together and he told me 9.5 to 1 although I find that hard to believe myself.

 

It has a tech3r on it so the person working on it now says that he can work around it somehow by adjusting the advance/retard within the computer system.

 

I personally would just like to know. All I know is it has JE forged pistons and Carillo rods, just trying to fill in the gaps on my end. I ran a compression check and its running around 125 psi on all six cylanders but I know that does not mean a lot.

 

The previous mechanic was going to go through his paperwork from last year and see if he could find the exact specs but if I can adjust it with a custom map than maybe its a moot point.

 

James