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    m30 compression test???

    when doing a compression on a 535i (e28) what should a good compression be???
    1989 325i SETA stroker [delphin] R3V'd 8/31/2011
    1989 325ix [zinnoberrot] $OLD
    1970 2002 [Nevada]

    Originally posted by Herr Faust Schinken
    guy must have slid into something that doesn't look like a car vs car hit
    Originally posted by ak-
    Must of slid into Rob

    #2
    190+/- 10% across the board should do ya. Whaddya have?
    1974.5 Jensen Healey : 2003 330i/5

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      #3
      100 and 105 peak..... what does this mean???

      anything i can do??
      1989 325i SETA stroker [delphin] R3V'd 8/31/2011
      1989 325ix [zinnoberrot] $OLD
      1970 2002 [Nevada]

      Originally posted by Herr Faust Schinken
      guy must have slid into something that doesn't look like a car vs car hit
      Originally posted by ak-
      Must of slid into Rob

      Comment


        #4
        Do a leakdown test. Are all the cylinders close to the same compression #'s?
        If the engine leakdowns well, cam timing is about the only thing that can bring down all your compression #'s equally.
        Lorin


        Originally posted by slammin.e28
        The M30 is God's engine.

        Comment


          #5
          Originally posted by LJ851 View Post
          Do a leakdown test. Are all the cylinders close to the same compression #'s?
          If the engine leakdowns well, cam timing is about the only thing that can bring down all your compression #'s equally.
          This.

          Also, did you hold the throttle open while doing the comp test? This will effect results. Usually if they are all about the same, it's a good sign, unless they are all abnormally low. I think mine were ~170-180 on my parts car before I tore the engine down for HG. (Two cyls were ~50-60). It ran great once I put the new,m uncracked, head on it.

          Leak down test is better anyways, and can tell you what is wrong, instead of something is wrong.
          1974.5 Jensen Healey : 2003 330i/5

          Comment


            #6
            Originally posted by slammin.e28guy View Post
            This.

            Also, did you hold the throttle open while doing the comp test? This will effect results.
            Thank you slambotron, i forgot to mention that!
            Lorin


            Originally posted by slammin.e28
            The M30 is God's engine.

            Comment


              #7
              Originally posted by LJ851 View Post
              Thank you slambotron, i forgot to mention that!
              I try to be the e28 master, I really do, lol.
              1974.5 Jensen Healey : 2003 330i/5

              Comment


                #8
                Also doing a compression check make sure your battery is charged rely good.
                Or have a battery charger on it.
                You don't want to mistake for low compression because the engine is barely turning over.

                :)
                Work We Do
                CAtuned Feedback Page|FB CAtuned Page
                http://www.catuned.com

                Comment


                  #9
                  If compression is even on all cylinders then your low numbers could be explained by method or cranking speed. Throttle wide open and be sure battery remains charged as slow cranking will effect results. Also watch how the needle rises with each compression stroke, a healthy engine will get most of the way there on the first stroke. The final reading is typically taken after three strokes.
                  A leakdown test will tell you more.
                  If the engine ran well and compression is even I'd not sweat the #s.

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