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Old 05-29-2009, 07:36 PM   #1
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Default Compression Readings

So i did a compression test on my miata today and the numbers came out like this: 1-185psi, 2-185psi, 3-170psi, 4-185psi.

I did a wet test and the number 3 went up to 190 or so. So I guess i have a bit of a problem with the number 3 cylinder. How bad is that? And the wet test pretty much shows that its the rings on that cylinder. I guess i can still drive like that but will it get worse over time?

I did not have the throttle at wot when i did this. Forgot about it. Will the reading be different if i floored the gas?
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Old 05-29-2009, 07:47 PM   #2
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Doesn't look too bad.
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Old 05-29-2009, 08:49 PM   #3
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Those readings are within specs.

If you truly want to know that sealing ability of the engine you must do a leak-down test.

Is there a problem with the engine that caused you to run a compression test.
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Old 05-29-2009, 09:03 PM   #4
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I have a leak down tester but i could not figure out how to get the cylinders to TDC. The engine runs great but i am burning or lousing oil somewhere. I posted a thread about that here before. The car does not smoke at all.
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Old 05-29-2009, 10:07 PM   #5
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A compression test is not going to tell you if you have oil burning issues. All a compression or leak down test will tell you is the ability of the cylinders to seal air...nothing else. You are barking up the wrong tree.

Depending on the mileage and maintenance you might need valve stem seals.
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