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Old 01-25-2007, 05:09 PM   #1
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Default compression test - *updated with numbers!!!*

Before I go and buy a DO WI kit I want to make sure the compression is good on my engine.

Its done 141,000 km now thats 87000 miles.

My tuners recommended i do so.

So what should I be firing on all for cylinders? whats a good reading and whats a bad reading?

cheers

Last edited by tabs604; 01-27-2007 at 09:45 AM.
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Old 01-25-2007, 05:13 PM   #2
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90 is bad, 130-150 has been common good compression in my experiences with Miatas. If one cylinder is way lower than the others then you have problems. If you find that you have low compression in a cylinder, put a spoon of oil in that cylinder. If the compression goes back up, then you know your rings are shot. If it doesn't go back up its your valves or something else.

Pull your injector relay and disconnect your coils when doing the test. Hold the throttle to the floor while cranking as well.

Not sure what else there is that you're supposed to do, i just know you don't want fuel spraying and it's hard on your coils to just crank like that.

EDIT: Also make sure your motor is warm as well.
Anything else I'm forgetting?
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Old 01-25-2007, 05:26 PM   #3
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the injector relay is the clip near the fuel rail right?

Everything looks right though...I've never heard anything more.
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Old 01-26-2007, 01:24 AM   #4
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comp test tells you jack. I've seen great numbers on a comp test and yet the car leaks air like crazy on a leak down test. If you want to be sure do a leak down test
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Old 01-26-2007, 01:28 AM   #5
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Yeah, leakdown FTW but simple compression for ease of being able to check for HUGE problems in your front yard with no compressor or access to one.
Not sure what the average shop charges for a leakdown test.
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Old 01-27-2007, 03:47 AM   #6
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cheers guys going to have it done today.
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Old 01-27-2007, 08:42 AM   #7
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so long as they are withing 10% or so and you are bove 130+psi you should be ok. Mine was 170 or so berfore. And the throttle plate does make a big difference i see about 40-50 psig more with it open. pumps up quicker to.
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Old 01-27-2007, 09:37 AM   #8
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Heres the results:

Dry Test

1 = 185

2 = 190

3 = 190

4= 190

Wet Test

1 = 215

2 = 220

3 = 215

4 = 215

My mechanic said thats fine considering the age of the car and wear and tear.

Now i'd like your opinions please.....
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Old 01-27-2007, 10:07 AM   #9
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I would have no complaints
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Old 01-27-2007, 10:29 AM   #10
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very nice results you obviusly take good care of the motor. Great job
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Old 01-27-2007, 12:00 PM   #11
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good results, go ahead with that WI.

FWIW, it's kinda weird considering you're already turbo that right before you do something that's going to protect your engine they want to check the compression. Just my opinion.
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Old 01-27-2007, 03:32 PM   #12
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knowledge is power and that is why some are weaker than others Koto
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