1988 BMW M5 compression

Tiny
NOMADAK
  • MEMBER
  • 1988 BMW M5
  • 6 CYL
  • 2WD
  • MANUAL
  • 11,500 MILES
I am trying to figure out what kind of results (psi) I should get if I do a compression test on my car. A lead BMW technician I talked to said 130-140 is good. Yet many other people I have talked to said they consistently get between 190-210 across all cylinders. Why the discrepancy? Should I be more concerned with higher numbers or just general consistency? (For what it's worth, BMW states this engine to be 9.8:1 compression). Thanks for your help.
Thursday, March 25th, 2010 AT 12:29 PM

2 Replies

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
I would be more concerned with consistant numbers.

If one cylinder is 20% less/more, that you have another problem.
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Friday, March 26th, 2010 AT 7:28 AM
Tiny
DOCHAGERTY
  • MECHANIC
  • 9,603 POSTS
I agree, consistency is more important. Also know that the S-88 motor, if unmodified (read: absolutely stock) and at that mileage, can have some issues. An inspection with a bore scope or camera inside each combustion chamber can be quite revealing. I have seen several with broken pistons still running. I am not ringing the alarm bell, I am just wanting to be sure you are an informed consumer. Especially considering the rebuilding and balancing costs for that motor. Ã â Â
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Saturday, March 27th, 2010 AT 8:52 AM

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