GSR Compression test

[Racer]

I was browsing my generic Honda Acura repair manual and notice that the according to the manual the standard compression for a GS-R is 270 psi. That seem kind of high so I decided to check the compression of my car. This is what I got:
C1 ? 170 psi
C2 ? 220 psi
C3 ? 200 psi
C4 ? 190 psi
If the 270 is real the numbers I got seem kind of low. I added a little bit of oil to C1 and redo the test and I got a 190 psi, not a big jump if the rings were bad. This is weird because my car does not consume or burn any oil (no smoke at full throttle), the coolant does not have any oil in it (i.e. I don?t think I have a bad head gasket.) The car has a smooth idle and I race my friends 96 GR-R and we were dead even from 0 to 110 mph. (we stop after that). Is there something wrong or the 270 psi is a typo. The compression tester was making a funny sound so I am not sure if it was bad or not. I do know that my brother tested his MX6 Turbo after that and he got 130 to 135 psi on all cylinders, which is what it should have (He recently rebuild the engine, it is a low compression turbo engine).

BTW. My car has 64K miles. I bought it used six months ago with 58K miles. It is not turbo or SC but I was thinking bout going to the dark side but with these numbers I am not usre if I should.

I only used battery power for the test and crank about 6 to 7 times. Should I expect 270 on a car with 64K miles. All 4 spark plugs looks about the same. No signs of oil or anything else. They were very clean but I do not know if that matters. The spark plugs are like 5K miles old.

What else should I check. I will most likely buy a new compression tester and test again. But I don't know what is the likelihood of having a bad compression tester. Not very likely I guess.

Any ideas?


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Milano Red 96 GS-R
AEM Cold Air Intake

[MarkC]

I get 225-230 every time I test mine.

It matters a lot how you perform the test. Key factors... Remove all spark plugs (not one at a time). And make sure you are holding the TB open )flooring it) when you are cranking.

The difference between all your cylinders sounds too high. Doesn't look right.

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Mark - Darth Boost - Turbo Mafia
98 Pearl Black GS-R, DRAG Gen. 3 Turbo
13.2 at 114MPH (GTech/Pro w/Drag Radials)

[RougeSol]

damnit I did mine and its 165 all across the board..... is that to low?


Matt

[redline]

were do you live? are you buring any oil? Does your car feel slow?

k

[Racer]

Matt,

Do you have a GSR or an LS? How many miles on the car? Are you turbo? For an LS that may be OK. Thats about 80 to 85% of the maximum compression for an LS. What wories me the most is the difference between cylinder at least in mine.


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Milano Red 96 GS-R
AEM Cold Air Intake
ITR Rear Swaybar

[aerodyne]

The manual is wrong. I have had a new blueprinted engine with about the same comp. ratio, and the compression was 210-220 psi.

I checked my '95 GSR at 60k, got about 220-230. I have been told it was very good.

Of course, I held the throttle wide open. I cranked for 10 sec on each cylinder.

Do a leak down test if you are concerned about your rings.

regards,

aerodyne

[rjaffey]

The factors MarkC mentioned are essential. Also remove the main fuse or unplug the main relay, so no fuel gets dumped in while you're cranking the engine.

Make sure your compression gauge is making a good seal in the spark plug hole. A small leak can make a huge difference.

The GSRs I've tested were all healthy were all in the 220psi range and were all within 5psi of each other.