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Discussion Starter · #1 ·
Just got done doing a compression test, I'm sure my neighbors loved that at 12:30 in the morning. Anyways here are the numbers:
1.165 3.188 5.185 2.185 4.175 6.160
#6 went up alot slower than the rest had to crank it longer. Not sure what thats all about? Look pretty good to me.
 

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Re: My compression numbers. (heathens)

Your number are very good. According to the MKIV Bentley (page 15d-2), new is 147-191 psi, the wear limit is 110 psi and there should be noe more than a 44 psi difference between highes and lowest. You're good on all three.
How many miles do you have? Based on your numbers, your mileage must not be too high. If it is, then all the better.
 

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Re: My compression numbers. (heathens)

I wonder what my numbers are like at 135k. I'll have to do the test soon and find out. I don't expect them to be that high, but I hope they're high enough that i won't have to consider a rebuild anytime soon.
 

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Re: My compression numbers. (rt30000)

Gauge is about $30. Plug it into the spark plug holes and crank the engine over (no plugs in).
 

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Re: My compression numbers. (SequoiaGLX)

Quote, originally posted by SequoiaGLX »
Gauge is about $30. Plug it into the spark plug holes and crank the engine over (no plugs in).

Any specific "good ones" to look for? Do we leave the other 5 spark plug holes open?
 

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Re: My compression numbers. (pal)

Yeah, test each one in turn. Take all the plugs out, screw the gauge into #1, crank it over with the starter a few times until the gauge stabilizes, read, let off the pressure, screw it into #2 and repeat, etc.
Somebody posted the spec out of the Bentley above for allowable numbers. I'm seeing 180-190 on all of mine with 115,000 miles, IMO that's freaking incredible. The wonders of Mobil 1.
 

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Re: My compression numbers. (SequoiaGLX)

Quote, originally posted by SequoiaGLX »
I'm seeing 180-190 on all of mine with 115,000 miles, IMO that's freaking incredible. The wonders of Mobil 1.

Wow! Maybe my expectations shouldn't be so low just because I've got a lot of miles. I'm even more anxious now to do the test on my engine.
 

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Re: My compression numbers. (SequoiaGLX)

Quote, originally posted by SequoiaGLX »
Yeah, test each one in turn. Take all the plugs out, screw the gauge into #1, crank it over with the starter a few times until the gauge stabilizes, read, let off the pressure, screw it into #2 and repeat, etc.

Make sure that you disable the ignition system by pulling the harness connector off the coilpack and the fuel injectors by pulling the appropriate fuse (#32 on the MKIV VR6). You don't want sparks and spraying fuel present during the test!
 

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Re: My compression numbers. (pal)

Quote, originally posted by pal »
Any specific "good ones" to look for? Do we leave the other 5 spark plug holes open?

The most critical thing is probably the accuracy of the gauge. I'm sure the $20-30 Craftsman one at Sears is pretty accurate. I plan on getting that one when I do the test.
Yes, the other 5 plug holes are open.
I'm going to write up the procedure from the MKIV Bentley in a thread. I'll post the link here when it's done.
 
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