Combustion chamber CC's

[defrag010]

I can't measure my heads because they are all cut up and dissassembled, so does anyone have the cc's of the VH45 combustion chamber from like a fsm or spec sheet or something?

[SSDwellah]

I have a first gen Q45 FSM at home. I can get it for you perhaps sometime tomorrow if its in there. If you need it tonight (late-night crackhead ) then you are out of luck.

[elwesso]

Someone else on here measured it, i think it was either ezekial or mettler...

[SSDwellah]

I just checked the FSM. I looked under the EM section (engine mechanical) and in the SDS subsection (service data and specifications) but they don't break that down. It may be elsewhere in that chapter where they talk about the cylinder head or you can derive it from the geometry measurements they give, but I am at work right now and I have midterm exams for grad school later so I won't be able to get it for you right now.

Sorry

[Q45tech]

The combustion space [heads plus gasket plus valve relief notches might be:

4494/8=561.75cc/10.2= 55 cc if CR is accurate so what say ~~ 50-51cc. [Guessing]

[the 300zx VG head is 49.5cc]..new VQ3.5 is 57cc.............1.0 CR point would be 5.875cc

The piston reliefs hold less than 0.5cc each and the gasket is thin and piston crown comes up - 0.002" from deck when cold [70F] probably flush at operating temperature.

[defrag010]

Thanks tech.. I was playing around with the calculator, and gave the pistons about -2cc volume for the reliefs and just played with the head cc number till I got what it claimed as stock compression - about 50-55cc.I'm doing the math for my new motor build and I couldn't belive I forgot one of the most important equations!!!

[Ezekial]

zerothread?id=159691

As it turns out ... those heads were not standard ... final figure was 59 cc

I have measured on another set of heads also ... 51cc

[gdz1la]

there is a cylinder head specialiest here in chch (named that) that does lots of 45's for stock car racing, he claimed that nissan cocked up the 10.2:1 ratio, and he claims he calulated 9.5:1 on nearly every one. whats every ones elses opinion, i want someone thats actually measured the pisotns domes and the head cc, not some maths nerd!i cant see why nissan would lie, but i also can see what a specialist whould miss calulate

[Q45tech]

Almost all manufacturers use optimistic numbers for CR worse case to account for deposits that may reduce combustion space.

Static CR is a meaningless number since CR assumes 100% air pressure getting into cylinders. Never happens except near torque peak rpm. [ VVT tuning and runner length 3rd order].

Running CR and CR at torque peak is what's important.

If the intake tuning rises to 107% VE at peak torque that would easily raise the effective CR ratio from 9.5 to 10.2 at that rpm.

Also measuring CR at room temp vs operating temp induces errors.

[sijoko]

there is a cylinder head specialiest here in chch (named that) that does lots of 45's for stock car racing, he claimed that nissan cocked up the 10.2:1 ratio, and he claims he calulated 9.5:1 on nearly every one.

Interesting bit of info there.

Didn't Ezekial get a lower than stated CR for his engine? If this is indeed the real CR, then it is another reason to turbocharge the VH45.

[maxnix]

Didn't Ezekial get a lower than stated CR for his engine? If this is indeed the real CR, then it is another reason to turbocharge the VH45.

Maybe yes, but probably with forged pistons. As Q45tech said, it is not static CR that is so important, but MEP.