compression test

[microgalant]

I have a 4g64 engine with 4g63 head wiseco piston 9:1.1,.20 over cometic head gasket, eagle rods.
Engine was built last year sept.
This year i put the turbo on, went dyno last week, and today i decided to do a compression test just to see if everything is ok.
1)120,2)120,3)125,4)125
Is that ok??

 

[starsthensun]

I'm pretty sure that 130 is the service limit. That's for 4g63 though, not sure if that makes a difference.

 

[68442]

They list general psi on this site.

http://www.geocities.com/dsmgrrrl/FAQs/compression.htm

 

[casper_talon]

I can't say what is the average for a 2.4L with 4G63 head, but my 2.0L 4G63 was 180psi on all 4 a couple of weeks ago. I was thinking yours might be a bit higher because of the larger block.

 

[toofast82]

that sounds a little low, when i had a 1g it was like 140-145 and when i had 2g it was about 155-160, i would think at least like 135

 

[GVR4592]

I would wait and see what other people with your engine combination have to say. Generally if the numbers are really close together, the engine is fine, but your numbers do seem really low. It could be the compression tester you are using isn't reading correctly.

 

[silver bullit]

When you where cranking the motor over where you flooring the gas peddle while cranking it?
If not try it again, 120 is very crapy for a 2.4.

 

[microgalant]

When you where cranking the motor over where you flooring the gas peddle while cranking it?
If not try it again, 120 is very crapy for a 2.4.

That was something that i didn't do.
Will try it again today, but do i have to remove all 4 sparkplug at the same time?

 

[turboglenn]

Having the gas pedal wide open makes a HUGE difference, you'll probably see 160psi or more doing that. You don't have to remove all 4 plugs, it's just nicer to your starter and lets the motor spin more freely to get a better reading.. Just make sure you unplug the injectors and plug wires if you do it without pulling all the plugs.

 

[Defiant]

You're seeing why a leakdown test is of more value than a compression test. The strength of your battery's charge and the health of the starter motor and its circuitry will also affect a compression test.

 

[TunaTalon]

You're seeing why a leakdown test is of more value than a compression test. The strength of your battery's charge and the health of the starter motor and its circuitry will also affect a compression test.

The cam profile will also affect a compression test. More aggressive cams hold the intake valve open longer after BDC lowering the effective compression.

The temperature of the block will also affect a compression test. A colder block will remove more of the heat of compression lowering the measured compression.