Announcement

Collapse
No announcement yet.

Dyno mystery. Need your help

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Dyno mystery. Need your help

    Car was running 100% when we pulled into the dyno garage. Ran great, idled great. Once it was bolted to the dyno, in neutral, BEFORE any pulls, -something- happened.

    What The F?

    Idle dropped from steady 1100 RPM to ~900 and stumbling

    AFRs went rich

    VE table is WAY low. In the 30s

    Car would not make low end power

    Tuner could not add timing without getting ping

    It backfired a couple of times. Never did that before, ever

    Nothing mechanically obvious (rattles, bangs)

    MAP & boost hoses all good and tight

    What in the frigging he'll could have happened? Maybe:

    1. Nuke timing gear slipped?
    2. Injector stuck open
    3. ?
    4. ?

    We're going to check 1, 2. Then test compression. I'm damn mystified. Any ideas?

    "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

    1987 E30 3L Turbo Stroker Das Beast
    2002 E39 M5

    #2
    Usually, the cause of a problem is very simple. #1 seems to make sense: if the timing gear slips, it could be the reason for backfiring.

    What does "VE table is WAY low. In the 30s" mean?

    Comment


      #3
      Compression check, leak check, timing check, fuel pressure, oil pressure ?
      89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

      new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

      Comment


        #4
        Check for spark. Was a spark plug wire dislodged while setting up the dyno? And why would it ping if AFRs are rich?
        '91 325i

        Comment


          #5
          1. Nuke timing gear slipped?
          2. Injector stuck open
          3. Compression
          4. Leak
          5. Fuel pressure
          6. Spark plugs
          7. Plug wires

          We'll be looking into all this. Still VERY frigging weird for the engine to suddenly go stupid rich
          "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

          1987 E30 3L Turbo Stroker Das Beast
          2002 E39 M5

          Comment


            #6
            FPR failure?
            Build thread

            Bimmerlabs

            Comment


              #7
              It was #1. Frigging adjustable timing gear threw a bolt and clocked to the stops

              "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

              1987 E30 3L Turbo Stroker Das Beast
              2002 E39 M5

              Comment


                #8
                Surprised by the lack of locking washers (serrated belleville type) under those screw heads. Do that in addition to thread locker if you decide to keep that pulley (I wouldn't keep it, if you're back to stock gasket thickness). Hopefully that pinging sound you described wasn't your valves making contact with the pistons.
                '91 325i

                Comment


                  #9
                  are you sure those bolts were properly torqued ?

                  also the lack of a washer under the central cam bolt should be rectified IMO as the bolt head doesnt have a big flange and high grade bolts onto AL is a risk of relaxation/loosening without a washer or lots of contact area

                  my guess (iirc its a 272 lobe and aftermarket deeper reliefs) is that you should be ok based on the exh valve to piston clearance is normally shedloads
                  89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                  new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                  Comment


                    #10
                    I -thought- they were properly torqued but obviously screwed it up. :-/ Nuke Gear is going in the trash. Back to stock.

                    Compression test after re-establishing timing will tell us if the valves survived. We had something like 0.125" p2v. Fingers crossed.
                    "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

                    1987 E30 3L Turbo Stroker Das Beast
                    2002 E39 M5

                    Comment


                      #11
                      Glad you found it and it was simple. funny because I have a cheap Chinese adjustable timing gear (even the +/- marks are labeled backwards) and it's worked perfectly for years.
                      Build thread

                      Bimmerlabs

                      Comment


                        #12
                        Originally posted by nando View Post
                        Glad you found it and it was simple. funny because I have a cheap Chinese adjustable timing gear (even the +/- marks are labeled backwards) and it's worked perfectly for years.
                        To be fair ive used my Nuke trouble free for the last 13 years and done at least 4 or 5 adjustments without issue (touch wood). It wouldn't be hard to design something better though. Moving around the cam was well worth the admission price from a power/torque improvement.
                        89 E30 325is Lachs Silber - currently M20B31, M20B33 in the works, stroked to the hilt...

                        new build thread http://www.r3vlimited.com/board/showthread.php?t=317505

                        Comment


                          #13
                          So who is actually running mechanical advance to make more power? How many degrees and with what cam? I'm running a 284/272.

                          Let's hear a roll call.
                          "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

                          1987 E30 3L Turbo Stroker Das Beast
                          2002 E39 M5

                          Comment


                            #14
                            I didn't use it to make more peak power necessarily - I used it to tweak the torque curve to get the most overall area, instead of a high peak (but losing torque/power everywhere else). There's a sweet spot where you don't lose much peak power but you get a lot more low end torque.

                            a bit of a pain to adjust on the dyno though, especially since I have a cam sensor and have to take all that apart to get to the timing gear.
                            Build thread

                            Bimmerlabs

                            Comment


                              #15
                              Thanks for the tip nando. We might keep the cam gear and dial in a bit of mechanical advance. How much does the M20 stock cam seem to like? We are running 284/272
                              "And then we broke the car. Again." Mark Donohue, "The Unfair Advantage"

                              1987 E30 3L Turbo Stroker Das Beast
                              2002 E39 M5

                              Comment

                              Working...
                              X