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Old 03-29-2008, 08:49 PM   #1
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Default Questions about my compression test.

This afternoon I did a compression test as I want to make sure everything is A-OK before the MS and turbo get here. The numbers were fine, between 180-190 across all cylinders but the spark plugs have me a little worried. Cylinder 1 and 3 had a light crescent of grey color half way around the porcelain next to the electrode. Number 3 looked clean and the porcelain was white. Number 4 was whitish on the ground strap and electrode and had specs. This one worried me most of all as I'm pretty sure that's a sign of detonation. I'm not sure what the grey crescent means on 1 and 3 but they all seem to be running hot. I'm using all oem stuff nkg blue wires and plugs. Should I have to go to a cooler plug on a stock car?

On another note, when cranking (only during the compression test) I hear one pop like popping a bottle cap off. Is that just my shitty compression tester or something else. Also, every time I went to touch the compression gauge after cranking I got a small shock. Bad engine ground? (CAS plug was removed for the test) Thanks.
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Old 03-29-2008, 10:10 PM   #2
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Those numbers don't look bad.

It might be more helpful to have some photos of the plugs.

You might also consider doing a coolant reroute, cold plugs and cold air intake when plumbing the turbo...they will make a huge difference as far as detonation control.

As far as the shocks when touching the compression tester...that might be from static electricity...getting in and out of the seat during the tests and then grounding out by touching the tester.
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Old 03-29-2008, 11:51 PM   #3
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yeah, maybe I'll try getting pics tomorrow. Like I said, the numbers are good but I don't understand why the plugs would indicate I'm running hot with 10* timing and 89 octane on a 100% stock motor.
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Old 03-29-2008, 11:55 PM   #4
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Meh, my 99 plugs did the same thing, slight little spots that indicate detonation. That was back when it was stock. I wouldn't worry about it. I know that sounds kinda dumb, but I don't think it was really a problem. I'd drop 1 heatrange cooler plug in it.
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Old 03-30-2008, 12:34 AM   #5
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Maybe your #4 injector is slightly clogged and is running a bit leaner than the rest. Plus the #4 cylinder is the one that supposedly runs hot due to the stock coolant flow setup, which could contribute to detonation.
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Old 03-30-2008, 12:39 AM   #6
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Quote:
Originally Posted by ZX-Tex View Post
Maybe your #4 injector is slightly clogged and is running a bit leaner than the rest. Plus the #4 cylinder is the one that supposedly runs hot due to the stock coolant flow setup, which could contribute to detonation.
i doubt the 4th injector being starved would hurt at stock or even low to mild boost
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