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Looking for clarification on going wasted spark with MS2PNP

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    Looking for clarification on going wasted spark with MS2PNP

    I have a MS2PNP that I ordered without the QuadSpark. After getting further into the turbo build, I have decided to go wasted spark and am looking for some clarification on what I need to make that happen.

    I'm all good on the coil packs and running those to the spark plugs. I am confused on 2 things.

    First, do I need anything additional (aside from the wires) in between the MS and the coil packs, or do I literally just run the wires from the coils to the appropriate serial pin? I've seen lots of people running that GM harness for their coils that they wire into their MS, but I do not know what version on MS they have and how that changes with what I have (MS2PNP).

    Second, as I understand it, the only need for a cam position sensor (CPS) is if I want to advance or retard timing. Everything will still run completely fine without one, or is a CPS 100% required for things to work?

    Thanks!


    1989 325i Alpine White
    69 STX

    #2
    I'm pretty positive the CPS is necessary for the engine to run, mostly because of spark timing, but also fuel timing. Without the CPS, how does the engine know where it is in the cycle, and whether it is on intake or exhaust. That is in the basic settings where you set up the 60-2 wheel and crank angle setting.

    There isn't a 'cam position sensor' on an m20, it is a 'crank position sensor' and sits by the water pump/ ac compressor reading the toothed harmonic balancer on the front of the engine. I'm assuming you're talking about the m20 here.

    Not sure on the wasted spark, my turbo car runs fine with the cap and rotor and regular coil/wires.
    318iS Track Rat :nice: www.drive4corners.com
    '86 325iX 3.1 Stroker Turbo '86 S38B36 325

    No one makes this car anymore. The government won't allow them, normal people won't buy them. So it's up to us: the freaks, the weirdos, the informed. To buy them, to appreciate them, and most importantly, to drive them.

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      #3
      Thanks for the info.

      Have you had any issues with spark blowout? What boost are you running?


      1989 325i Alpine White
      69 STX

      Comment


        #4
        Originally posted by MisterMiniS View Post
        Thanks for the info.

        Have you had any issues with spark blowout? What boost are you running?
        I had some sort of issue a while back but hadn't changed the plugs in a couple years. I replaced them with some new BPR7ES and it fixed the issue.I'm at 6-8 psi but have been up to 10 without problem. I never saw the point of wasted spark besides removing the maintenance items of the cap rotors and wires/coil.
        318iS Track Rat :nice: www.drive4corners.com
        '86 325iX 3.1 Stroker Turbo '86 S38B36 325

        No one makes this car anymore. The government won't allow them, normal people won't buy them. So it's up to us: the freaks, the weirdos, the informed. To buy them, to appreciate them, and most importantly, to drive them.

        Comment


          #5
          Originally posted by downforce22 View Post
          I'm pretty positive the CPS is necessary for the engine to run, mostly because of spark timing, but also fuel timing. Without the CPS, how does the engine know where it is in the cycle, and whether it is on intake or exhaust. That is in the basic settings where you set up the 60-2 wheel and crank angle setting.

          There isn't a 'cam position sensor' on an m20, it is a 'crank position sensor' and sits by the water pump/ ac compressor reading the toothed harmonic balancer on the front of the engine. I'm assuming you're talking about the m20 here.

          Not sure on the wasted spark, my turbo car runs fine with the cap and rotor and regular coil/wires.
          crankshaft position sensor is required - a camshaft sensor is not used at all for wasted spark. If you want full sequential spark/ignition, yes, but that's not what he's asking.

          for wasted spark, you don't need a cam sensor at all. The reason is because each coil fires twice per cycle (once in the intake stroke and once on the exhaust), thus the "wasted" spark.
          Build thread

          Bimmerlabs

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            #6
            I assume the quad spark is the external igniter.

            Do your coils have inbuilt igniters? If they do you can run them straight to the MS. But if they don't, you'll need an external igniter of some sort (the quad spark thing).

            But you can get GM Bosch igniters from all kinds of cars at the wreckers. Just make sure its the "dumb" kind that doesn't have inbuilt dwell. You want to control the dwell from the ECU.

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              #7
              Depending on what plug and play unit you have, there may already be provisions for it, if not the mods are simple. Coils with integral drivers or coils driven by a high current transistor in the megasquirt, no cam position sensor is required in any case.

              For what it's worth I am running 14psi (15 peak) with a mostly stock ignition system. Only an old MSD Blaster 2 coil and plugs gapped down to 0.022". Once I find the limits of my particular configuration I will certainly report on it, but I believe people have pushed a system like mine harder.

              Originally posted by e30davie View Post
              Do your coils have inbuilt igniters? If they do you can run them straight to the MS. But if they don't, you'll need an external igniter of some sort (the quad spark thing).
              Not quite, you can directly drive coils with megasquirt if it's equipped with the proper high current transistors. Instead of a logic level signal from the megasquirt triggering an external transistor you just wind up switching the coil's ground directly at the megasquirt.
              Last edited by varg; 06-07-2017, 06:48 PM.

              IG @turbovarg
              '91 318is, M20 turbo
              [CoTM: 4-18]
              '94 525iT slicktop, M50B30 + S362SX-E, 600WHP DD or bust
              - updated 1-26

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                #8
                Awesome guys! Thanks for the good info. I appreciate it.


                1989 325i Alpine White
                69 STX

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                  #9
                  If you bought the MSPNP2 that has the provision for waste spark install but without the ignition drivers, you must use an ignition driver such as the quad spark. From there its as simple as wiring the quad spark into the megasquirt, getting a GMDIS plate and rewiring the internals for the coils and wire the quadspark to the GMDIS board. I wired mine in last year and it took probably 3 hours from start to finish.

                  From there all you need to run the car is a CPS and changing the settings in megasquirt for waste spark. I run 3.0ms dwell and 1.0ms spark duration and have no spark blowout with bpr7es at 0.025" at 14 lbs of boost.

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