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Forum namePerformance/Engine
Topic subjectcompression question..
Topic URLhttps://forums.2gnt.com/dcboard.php?az=show_topic&forum=i5&topic_id=17684
17684, compression question..
Posted by larrlarr74, Mar-17-02 12:13 PM
my buddy had a compression test ran on his eclipse and they told him that the 3rd cylinder had 25psi less than 1,2 and 4 cylinders. what is the compression supposed to be per cylinder on average and if the compression is off like that can that cause the cat converter to go bad in like 3 days? is 25psi lower compression bad enough to where you would have to rebuild the block and if so what would he have to do to get it fixed...rings, new head, valves? the car runs good though and doesnt seem to have any problems except it shot out the converter in three days..thanks
17685, RE: compression question..
Posted by larrlarr74, Mar-17-02 10:31 PM
what does no one know anything about compression???i guess not!
17686, RE: compression question..
Posted by Fast420A, Mar-18-02 12:01 AM
>my buddy had a compression test ran on his eclipse and they
>told him that the 3rd cylinder had 25psi less than 1,2 and 4
>cylinders.

Thats a bad thing.

what is the compression supposed to be per
>cylinder on average

Between 160 - 220
and if the compression is off like that
>can that cause the cat converter to go bad in like 3 days?

I don't see how that could make the cat go bad.

>is 25psi lower compression bad enough to where you would
>have to rebuild the block and if so what would he have to do
>to get it fixed...rings, new head, valves?

Well that all depends on the REASON for the low compression. Did you run a wet compression test by adding a spoonful of oil to the cylender and doing the test? This will tell you if the rings are bad or not. If the number goes up after adding oil, the rings are the most likely cause. If it's not the rings then it could be a cracked piston, or valves. You also need to run a leak down test. That will tell you if the valves are sealing correctly.

the car runs good
>though and doesnt seem to have any problems except it shot
>out the converter in three days..thanks

The car may seem ok but it does need to be fixed if he wants it running to the full potential. Good luck.



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17687, RE: compression question..
Posted by larrlarr74, Mar-18-02 12:19 AM
thanks man thats the info i needed
17688, RE: compression question..
Posted by larrlarr74, Mar-18-02 12:21 AM
oh yeah what is a leak down test?
17689, RE: compression question..
Posted by mkerley, Mar-18-02 02:08 AM
http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm
17690, RE: compression question..
Posted by larrlarr74, Mar-18-02 05:09 AM
wow that really breaks it down huh!thanks