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Old 06-17-2003, 04:59 PM   #1
Jaxx
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Default compression test numbers

what kind of compression numbers should i be looking for

a compression test yielded
1 125
2 114
3 130
4 125

2 is lower than the rest but the big question is are ALL the cyls lower than they should be
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Old 06-17-2003, 06:51 PM   #2
WRX 555 STi
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Yep. You should NOT see anything less than 168psi or more than 178psi (+/- 2psi). Your engine is losing some compression. Did you beat on it when you bouht it? The rings don't usually sit good on the cylinder walls if you really beat on the car while it's still under 500 to 1000 miles.

~Anthony.
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Old 06-17-2003, 06:53 PM   #3
WRX 555 STi
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Oh, i didn't see you have an EJ20 (?). In that case, i don't really know those numbers. I thought this was an RS-T only forum...hmmmm...

~Anthony.
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Old 06-17-2003, 11:59 PM   #4
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Hey Anthony! Not all RS-T's have those numbers for compression, at least for the 8.5 to 1 ratio guys. I am curious why this guys #2 numbers are so much lower than the rest. It may be a washed set of rings. I would expect a CEL light if that was the case. Running too rich would cause this to happen.
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Old 06-18-2003, 01:29 AM   #5
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For what it's worth I was seeing 198-200psi across the board in my 98. I've always thought as long as they're somewhat equal or within 10% or so of each other its not too bad.

I know even with dsm's it's ok if they're in the 120's and they're 7.8:1 on the 6 bolt engines.


As for the rings, I think running them hard at first will seal them better initially but will ruin the longevity of the engine..so you will see a decrease in compression if that it is the case.


edit: if you're not seeing that great of compression crank up the boost...more blow by = more opportunity for boost..j/k
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Old 06-18-2003, 01:31 AM   #6
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Here's what I managed to find from the 02 WRX manual
DOHC Engine Page ME-22

Standard:

138-166 psi

Limit:

121 psi

Difference between cyls:

7 psi


Hmmm, kinda borderline. How was it running? Sorry if I didn't catch the background story.
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Old 06-18-2003, 01:48 AM   #7
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Testing the motor cold can result in a good amount lower numbers, BTW. Keep that in mind as you're looking at compression numbers from manuals versus your results... the books all test them hot.
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Old 06-18-2003, 09:45 AM   #8
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Here's what the JDM manual says:

Standard - 142-171psi
Limit - 121psi
Difference between cylinders - 28psi

It is better to test a warm engine.
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Old 06-18-2003, 10:53 AM   #9
Jaxx
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yes it was cold .. and it was on the ej20G .. which i *think* is 8 to 1 like the ej205 ... but there has been suggestion that it is 8.5 or 8.8 to 1 in whcih case it is hosed ...

the proublem is that i have about --><-- skill tuning the tec 2 .. if i stay out of boost i am fine quite peppey actually..once i hit ~110 kpa it falls on its face oh yeah and the turbo seals are bad so it smokes
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Old 06-18-2003, 11:48 AM   #10
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The manuals I have are for the EJ20G too.

Sounds like it needs some work.
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Old 06-20-2003, 02:00 PM   #11
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Well, try this...put a bit of ATF in it and crank again..if it goes up dramatically, the rings are worn, if not, its in the head.

Those numbers are borderline being acceptable, as its around a 10% difference across the cylinders

Adam
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Old 06-20-2003, 03:16 PM   #12
Jaxx
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could i have screwed up somthing with the timing belt?
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Old 07-01-2003, 09:32 PM   #13
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so i heated the engine up today (coolant to 88C)

and re did the compression test

got 130 psi +- 1psi in all cylinders
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Old 07-02-2003, 02:31 PM   #14
stimpy
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That's a good sign. Now you just need to check turbo bushings and main bearings

-Jon
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