Compression Test Results

[Mumbo#5]

Hi all

Just did a compression test on my car and i got what seems to me to be fairly low compression. All of the cylinders were 10 psi within each other at 120-130psi. I did the test at NOT.

The engine has been rebuilt about 10,000kms ago and has arias forged pistons, 20thou over and 4 thou ring gap.

Can anyone shed some light on why its so low? or is it normal??

Thanks in advance

[Guilt-Toy]

i compression tested my engine 800km after it was built and i got a reading of 120 in each cyl. yes it is a bit low in compression but that good thing about that is that its safe to run high boost and high ignition timing so the only difference you will notice to a engine with 160 - 170 compression is the driveability off boost (mine is a 3 litre so its still really good anyway) and you can run more boost and more timing then they can...

Hi all

Just did a compression test on my car and i got what seems to me to be fairly low compression. All of the cylinders were 10 psi within each other at 120-130psi. I did the test at NOT.

The engine has been rebuilt about 10,000kms ago and has arias forged pistons, 20thou over and 4 thou ring gap.

Can anyone shed some light on why its so low? or is it normal??

Thanks in advance

[Nabil]

I assume your engine builder has either deliberately or accidently,

blueprinted your engine with a lower compression ratio.

Possibly made an error in calculating your desired compression ratio.

Could be anything from the thickness of the head gasket, pistons used, the

amount the head/block was decked etc.

This just means your engine will be more less likely to detonate

than another engine with a higher comp. ratio.

Cheers,

Bill

[Guilt-Toy]

i think my head gasket has something to do with it.. its 2mm i think

[No Crust Racing]

As long as compression is more or less even you're fine.

[Mumbo#5]

its got a standard nissan headgasket with ARP studs. I didnt do the test with the injectors not operating so this could have also gave me a lower reading. The workshop that put my engine together new I was eventually going to run really quite high boost so I'm guessin they did that to suite.

Sweet thanks lads

[wrxhoon]

Hi all

Just did a compression test on my car and i got what seems to me to be fairly low compression. All of the cylinders were 10 psi within each other at 120-130psi. I did the test at NOT.

The engine has been rebuilt about 10,000kms ago and has arias forged pistons, 20thou over and 4 thou ring gap.

Can anyone shed some light on why its so low? or is it normal??

Thanks in advance

Thats big variance for a new engine , it should be a lot closer, thats the worry not the numbers, numbers will depend on lots of things , even the gauge the way you done the test etc....

I hope you have more than 4 thou ring gap otherwise you will have broken rings, unless you mean 4" piston to bore clearance .....