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  • S15 cutting out at high boost?

    I am at my wits end with trying to figure out a cut out issue the car has above 21psi.
    98 240sx w/ stock long block S15 sr20det, rewired walbro, fmic, 20g turbo w/ internal gate, enthalpy tuned ecu, z32 maf, 3in exhaust and progressive methanol injection by alkycontrol.com

    Ok heres what it does. under 21psi it runs perfectly fine. Pulls to 7800 with no problems.
    If i try to turn the boost up past 21 at wot it will cut out right about when it hits full boost, it doesn't sputter it flat cuts out like you lifted your foot off the gas right about when it hits full boost. It will cut out then back in like twice then start pulling again.
    I have tried adding additional grounds to the engine as well as a coil pack grounding plate, replaced the coil pack harness with a new one from wire specialties, tried swapping in some 350z coils, closed the gap up to .020.
    tested to see that the harness is getting proper voltage to the coils, ran 12v power to the harness strait off the battery, voltage stays about 13.3-13.5 through the pull. I`m starting to think this issue is not spark related.
    a/f is good. Ive tried leaning it down a bit as well as richening it up some through the alcohol injection just for something to try.

    None of these thing made any difference at all. Still will cut in and out if i go above 21psi.

    car has a blitz spec r boost controller and have swapped it out for a manual boost controller just to make sure thats not the problem and no change.

    Does anyone know if there could be anything in the factory S15 ecu that would cause fuel cut? Car is running a Z32 maf and has a rom tune by RS Enthalpy.
    would love any suggestions that maybe i`m not thinking to test.
    98 240sx w/ S15 SR20DET, TD06 20g, FMIC, 3in exhuast, walbro, EBC,

  • #2
    What plugs are you running? Try BKR7EIX or BKR8EIX if you go to the track. I bet it fixes your problem. Copper plugs are junk.
    '18 Chevrolet Volt - Electric fun hatch for DD duty!


    DefSport Koni Sleeve and Spring Perch Buy!!!
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    • #3
      Using BKR7e
      Always was under the impression copper was the best conductor and the iridium simply offered the longevity of platinum with near copper performance. But I'll try anything at this point.
      98 240sx w/ S15 SR20DET, TD06 20g, FMIC, 3in exhuast, walbro, EBC,

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      • #4
        Copper plugs try to create a voltage potential over too large of an area. Sounds like you have an ignition problem, go with iridium plugs.

        Copper plug advice was good back in 1993, not do much now.
        '18 Chevrolet Volt - Electric fun hatch for DD duty!


        DefSport Koni Sleeve and Spring Perch Buy!!!
        http://www.nissanroadracing.com/showthread.php?t=5902

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        • #5
          Originally posted by Def View Post
          Copper plugs try to create a voltage potential over too large of an area. Sounds like you have an ignition problem, go with iridium plugs.

          Copper plug advice was good back in 1993, not do much now.
          I will definitely try then thanks. I have felt it was ignition from the start. That's why all my testing has been mostly around the ignition. I use ngk copper plugs in my 650hp Galant. Didn't really expect they could be a problem. But there's a easy way to find out.
          98 240sx w/ S15 SR20DET, TD06 20g, FMIC, 3in exhuast, walbro, EBC,

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          • #6
            i've had good luck with coppers. iridiums work but are expensive. i run the bcpr7es, not the bkr7es. slightly different length (does not affect the combustion side).. so same plug. What gap are you running? Try .6mm. doh just saw the gap you are running. get new plugs gapped at .5 or .6mm.

            Are you maxing your MAF? maybe you are unable to meter more air.. and fueling isn't keeping up. but your motor would probably have popped by now. Check with Enthalpy and see if there is some fuel cut when you reach close to max on the injectors or MAF voltage.
            Last edited by gawdzilla; 11-07-2013, 11:48 AM.

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            • #7
              I don't see how I could be out flowing a Z32 maf at 350hp.
              I am monitoring afr's and the car isn't going lean. I keep it on the rich side.
              98 240sx w/ S15 SR20DET, TD06 20g, FMIC, 3in exhuast, walbro, EBC,

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              • #8
                I've fixed multiple cars with a high boost misfire by going from old coppers to iridiums. They're like $28 a set and last 10x longer than copper plugs that cost about $15/set. How is that expensive? It's like 4-5 gallons of gas.
                '18 Chevrolet Volt - Electric fun hatch for DD duty!


                DefSport Koni Sleeve and Spring Perch Buy!!!
                http://www.nissanroadracing.com/showthread.php?t=5902

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                • #9
                  As I suspected the plugs changed nothing. Same cut out above 21psi even with BKR7eix gapped at .020
                  98 240sx w/ S15 SR20DET, TD06 20g, FMIC, 3in exhuast, walbro, EBC,

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                  • #10
                    does the enthalpy tune have some safety at close to max injector duty cycle? i know on the pfc you can have it trigger a warning.

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                    • #11
                      Does it do it at higher and lower rpm? What are the afrs when it cuts out?
                      '18 Chevrolet Volt - Electric fun hatch for DD duty!


                      DefSport Koni Sleeve and Spring Perch Buy!!!
                      http://www.nissanroadracing.com/showthread.php?t=5902

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                      • #12
                        According to Martin there is nothing in the ecu that would just cut fuel. I considered this as I'm using stock 480 injectors. I wasn't sure if the ecu could be cutting fuel thinking it couldn't possibly give the car enough fuel at the airflow I'm at and it doesn't know about all the alcohol I'm injecting. But he says he doesn't see anywhere in the ecu it would cut fuel.
                        Afr is high 10 to low 11 until it cuts out. They then leans out to 12's during cut out.
                        98 240sx w/ S15 SR20DET, TD06 20g, FMIC, 3in exhuast, walbro, EBC,

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                        • #13
                          There's a ttp max setting that I'm not sure if it clamps the load at that setting or acts as a cut when it's exceeded. It is a 2d table with rpm on the x axis.

                          Epstein would definitely know what it triggers in the ecu (fuel cut or not).
                          '18 Chevrolet Volt - Electric fun hatch for DD duty!


                          DefSport Koni Sleeve and Spring Perch Buy!!!
                          http://www.nissanroadracing.com/showthread.php?t=5902

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                          • #14
                            Originally posted by Def View Post
                            There's a ttp max setting that I'm not sure if it clamps the load at that setting or acts as a cut when it's exceeded. It is a 2d table with rpm on the x axis.

                            Epstein would definitely know what it triggers in the ecu (fuel cut or not).

                            So its possible that if TTP is exceeded the ecu will just cut fuel altogether even in a S15 ecu.
                            I think I need to just put bigger injectors in even though im using alcohol injection for extra fuel.

                            Epstein, now thats a name I havent heard in a long time assuming its Epstein from the Tampa area.
                            98 240sx w/ S15 SR20DET, TD06 20g, FMIC, 3in exhuast, walbro, EBC,

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                            • #15
                              Yep, he pops by here every once in a while.

                              The TTP max value maybe the issue, I really don't know what it does, as I always put it to 255 on my tunes and never came remotely close to that in calculated load.
                              '18 Chevrolet Volt - Electric fun hatch for DD duty!


                              DefSport Koni Sleeve and Spring Perch Buy!!!
                              http://www.nissanroadracing.com/showthread.php?t=5902

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