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Old 04-29-2001, 12:09 AM   #1
BlueRidgeRS
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Member#: 1953
Join Date: Jul 2000
Location: Lakeland, Florida
Vehicle:
2002 WRX SportWagon
Platinum Silver

Post Compression test

Bought a compression tester kit and these are the numbers I got:

Cylinder #1 - 205 psi
#2 - 205 psi
#3 - 215 psi
#4 - 220 psi

They seem high to me but this is my first Subaru so this might be normal. I have a Maxima SE and all cylinders came up around 173 psi. V6 vs. H4 might explain the big difference. The engine is stock except for a K&N drop-in filter. It's got over 10K miles. Has anyone else done a test like this?
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Old 04-29-2001, 12:50 AM   #2
jhuang76
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I want to state that I've never ran a compression test (seen it done as a bystander).

How many miles does your Maxima SE have? 10K for an engine is nothing (esp. a Subaru one which is pretty tight in the first place) and I'd expect it to have a very small leak.

As a rule of thumb, your pistons will leak more as the engine gets older (see more miles).
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Old 04-29-2001, 03:50 PM   #3
BlueRidgeRS
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The Maxima has 176K miles on it. Chilton's service manual for the Maxima states the 173 psi is the max for this engine.

I basically did the test to get a baseline of a fairly new engine. That way I'll know if it's leaking and also see how the engine is wearing over time.
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Old 04-30-2001, 09:07 PM   #4
SubyTechMaster
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'04 08 Tribeca, SVX
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Wink

If your RS is a Phase I or Phase II motor the Spec. from Subaru is 185psi @ 350RPM. Since you are over that spec., you are probably spinning much faster.
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Old 05-01-2001, 03:01 PM   #5
BlueRidgeRS
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I've got a MY00, so are the results normal? And why are cyl. 3 & 4 higher than 1 & 2? Shouldn't they all be uniform?
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Old 05-01-2001, 06:03 PM   #6
SubyTechMaster
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Yes, even the lowly '99 with only 9.7/1 compression has the same specification.

General rule is you want all the cylinders to be within 10% of each other. There are too many variables to affect compression; speed the motor is cranking, carbon build-up, oil in cylinders, fuel in cylinders, etc.

If you are really concerned about low compression, the next step would be a wet compression test or take it to an experianced Technician.

You can't compare figures with a differant kind of motor or even differant year/same motor. A V6 Nissan has less compression and more friction, it spins slower.

The purpose of this was a baseline. Go enjoy your car and put another 10,000 miles on it and check it again. Make sure you note as many variables as you can think of; Engine temp, oil viscosity, battery health, etc.
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Old 05-02-2001, 01:46 AM   #7
Thug
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But the MY00+ supposedly have 10:1 compression. So it would be higher than a '99 on a compression tester.
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