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  • Uneven Spark Plug Readings......

    I am still going through the daunting process of fine tuning the LENZ and have a few issues to resolve. One of them is the uneven spark plug readings. I posted a while back about TB measurement sync and as it turns out my TB's are dialed in. I have synched the TB's with the carbtune, replaced/sealed all possible intake leaks, but my plugs are still not reading even. They are pretty far off from each other. The #1 cylinder (closest to firewall) is black rich (center electrode, strap and plug rim). The #3 cylinder is less so (nearly a perfect plug reading, brownish center, heat range on strap halfway up). The #2 cyl is on the lean side (whiter center, second half of strap whiter then 1st half). The #4 plug is dead lean (white ashy center, whole strap is whiter). I have monitored my AFR's with a stand alone WBO2 and they are where they should be, 12.6-13 from 3800-redline. When I did the TB vacuum sync, I went off idle to around 2K just to see what it would read. The carbtune sticks read the same as the plugs (off idle, it is even at idle) in that the #1 cyl is lowest vacuum and the #4 is way higher? Are there any other things that I can tune maintenance wise to even out this difference of airflow to the cylinders? I have a carbon airbox with the external filter housing if that has anything to do with it?

    Plug on the left is closest to the firewall.


    Engine specs:
    LENZ standalone EMS
    Stock 2.3l bottom with 126k, new rod bearings, and oil pump. Compression #'s are all in the high 190's, never had leakdown.
    Carbon airbox with external filter housing and stock size K&N panel filter, oiled
    real 48mm TB's, measured three different throttle openings and all were within +/- 1mm.
    EVO intake blocks (new)
    Head ported, intake only, to match EVO intake blocks
    30lb (new) Accel injectors (not flow balanced? maybe this could be the culprit?)
    BMP adj FPR running at 45psi (still testing fuel pressures for best setup)
    Schrick 284/276 dialed to spec with turner gears
    XR4CS, stock gap
    Magnacors (just checked all of the plug ends and crimped them for a better clasp of the plug)
    New rotor and cap
    50/50 header with O2 mounted in lower crossover point
    50mm SS race center, with WBO2 in X pipe, and dual 3" resonators
    50mm race mufler

    T

  • #2
    the first thing I'd do is get a leakdown test to see if those results correlate with the vacuum readings
    Last edited by TeamM3; 08-28-2004, 08:19 AM.
    A friend will come bail you out of jail, but a TRUE friend will be sitting next to you in the jail cell saying, "Dude, that was focking awesome!"

    Comment


    • #3
      Originally posted by TeamM3
      the first thing I'd do is get a leakdown test to see if those results correlate with the vacuum readings
      I just had the head rebuilt (ported, seals, seats....etc). This shouldn't be an issue. I'll check into it though.

      T

      Comment


      • #4
        Hey , you are not alone :0)
        Here are my plugs for a comparison.
        I was very insecure about cyl 2, wich looked lean.
        I also run a airbox & A/N.
        My WB readings show 12,2- 12,6.
        But I dont know more (or what to do)

        Plugs are NGK D7EA.
        Every thing other than A/N & airbox is stock.

        Daniel
        www.m3e30.ch

        Comment


        • #5
          Originally posted by TeamM3
          the first thing I'd do is get a leakdown test to see if those results correlate with the vacuum readings
          I agree.

          I just had Mario at VSR do a leak down and compression test on my motor. As with your motor my compression numbers were great, all around 203lb. But my leak down numbers were really bad, ~42% across the board. As far as we could tell all of the leakage was past the rings, there was no evidence of leakage at the valves.

          The only good thing about my numbers is that they are even, all within +-10 of each other. So the car still idles and pulls smooth.

          My motor: Stock 2.3, 147k Miles, 11 track/autox days on the motor since I've owned it.

          Comment


          • #6
            Mick,

            if you don't mind me asking, with such high leakdown percentages how much power did your car put down on the dyno if you've ever had it dynoed, and what kind of dyno was used?

            Chris W.

            Comment


            • #7
              I've never had it on a dyno but I'd love to find out.

              The motor is still in the car, I beat the pants off of it regularly. The only ill effects I notice are; oil gets funked up quickly especially after a track day, car's down on power, there is a bit of piston slap on cold start.
              On the up side; It dosen't blow any smoke, burns very little oil, the plugs always look fine, passed MA emmisions with flying colors, and it pulls reasonably well up to redline all things considered.

              Tony,
              Sorry to run this thread off topic. Wish I could help.

              Comment


              • #8
                Tony,

                Have you used different plugs before? If so, how were the readings on them?

                Comment


                • #9
                  Originally posted by Bavarian3
                  Tony,

                  Have you used different plugs before? If so, how were the readings on them?
                  Just X5DC's up until I made the move to the 48's, CF airbox, ported head....etc. On some of the logging of the AFR's with my old setup, there was some serious misfire above 6500. With the XR4CS, no more misfire readings.

                  T

                  Comment


                  • #10
                    why do you have so much crap on the plug threads? daniel to some extent also.
                    when I pull my plugs out the threads are almost squeky clean. daniels plugs look ok,
                    except for number 2 looks real clean.

                    are these plugs pulled right after a hard run with no idling?

                    ive run some x5dtc briefly and they were nearly white, with the A55V the plug is soot dark and
                    the isolator is clean. the AFR 12.5-13.0 on full throttle is rich enough. the reading is
                    consistent on all cylinders.

                    anyway, I dont believe its the plugs.
                    leak down test as others have said.
                    and are the injectors balanced?

                    John
                    Last edited by John; 08-30-2004, 06:15 AM.

                    Comment


                    • #11
                      Pardon my ignorance, but what sort of numbers/result do you expect from a leak-down test? I know it checks for leaking valves or rings, but what sort of time and what pressure do you hold it at. Also, what is acceptable and what is a fail. (I'd like to rig up this test on mine).
                      Cheers
                      Steve
                      Scottish Cecotto

                      Comment


                      • #12
                        Depends on the machine used for the leak down test:evil: Normaly in a good engine you can reach 5-15% leakage, over that is not perfect.
                        In order to determine if you have leakage over the piston rings, squirt a bit of oil in (that will improve piston ring sealing) and turn the engine a few times.
                        45%, certainly someth is wrong

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                        • #13
                          Originally posted by John
                          why do you have so much crap on the plug threads? daniel to some extent also.
                          when I pull my plugs out the threads are almost squeky clean. daniels plugs look ok,
                          except for number 2 looks real clean.

                          are these plugs pulled right after a hard run with no idling?

                          ive run some x5dtc briefly and they were nearly white, with the A55V the plug is soot dark and
                          the isolator is clean. the AFR 12.5-13.0 on full throttle is rich enough. the reading is
                          consistent on all cylinders.

                          anyway, I dont believe its the plugs.
                          leak down test as others have said.
                          and are the injectors balanced?

                          John
                          Hi John

                          There is some crap on my threads, because my head
                          was never apart from the block.
                          Is there a good way to clean the threads without
                          disassembling ?

                          The plugs were not pulled as they should, without idling.
                          They where used on the Ring
                          The photo I tooked was after 500km Autobahn WOT
                          with a few minutes idling. -Think that should not cover up the spark after that long run.

                          I used my green Injectors right out of the box.
                          I hope they are balanced....


                          Daniel
                          www.m3e30.ch

                          Comment


                          • #14
                            so i appear to be running lean :sosad:
                            ....at least its consistent across all the cylinders



                            they arent as white as they look in that picture due to the flash...they are more of a light brown

                            i need to do some tuning huh?

                            Comment


                            • #15
                              Just a tad bit...

                              Tony,

                              Did you figure out the problem?

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