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  • Hard Cut-Out @ 3500RPM?

    So I finally got the Meqasquirt working ... just obviously not tuned. Everytime the car starts to spool into boost (around 3500RPM) it will back-fire .. and jerk violently.

    For ignition I have: NGKZFR7's gapped to .030", Stock Distributor w/ HEI.
    For fuel I have: Milli S injectors @ 70psi, 6psi WG, 255lph Walbro.

    I'm not sure if loading a Datalog will help but I uploaded in case. HERE!

    (I'm @5000ft, so atmosphere here is 83kPa)

    Any ideas? The motor is warmed up and around 165 degrees. The car also runs fine N/A through to redline. Sorry, I don't have the AFR's yet.
    Last edited by ExtremeJDK; February 19, 2009, 01:01 PM.

  • #2
    I'm not sure if the altitude would have an impact on this suggestion but here it goes:

    Gap your plugs down to the .024-.026" range, you could be blowing out spark as boost builds. Since you're still on a disty do all the basic checks like cap/rotor cracks as well. More often then not I find that spark blowout comes from faulty hardware in the engine bay such as plugs/wires/cap/rotor.

    Is your MS required fuel set up for the effective flow rate of the 280s @ 70psi?

    92 MX3 Turbo ($100 junkyard KLG4) 11.904 @ 124.3mph, 14psi, DOT approved Hoosier drags, pump gas.
    HIN/NOPI Supershow Class Winner - Miami 2010 - Street-Sport Compact-Mazda
    Links: Pretty Pic, GoFast Pic, Timeslip, Track Video, Dyno Video
    As of July 2011 the MX3 has been retired and sold.

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    • #3
      im going to say your to rich and your making it harder for the spark to burn the fule this putting fuel in the hot piping and it back fires. i have been here when tuning with high fule prasser also when you know afr's this will help point out what is wrong
      Last edited by lthomas2g; February 19, 2009, 02:38 PM.
      http://valid.canardpc.com/cache/banner/2653387.png

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      • #4
        For anyone who isn't at a computer with a LogViewer ... here is a screen-shot I saved in JPEG. This is a 1st and 2nd gear WOT pull.

        Last edited by ExtremeJDK; February 19, 2009, 04:30 PM.

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        • #5
          From the looks of that graph, you are definitely having intermittent spark problems (aka blowing out spark) I'd venture to say, go as low as .22-.24 on the plugs.

          I was out helping datalog on Crome in a buddys Turbo'ed GSR the other day, and the same thing happened, it was a combination of having too hot of plugs, coupled with a large gap, and as we would do pulls, and it would braaap braaap and blow spark out/cut out, gapped the plugs to .22 and that thing ran perfect, with no hiccups.

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          • #6
            I just realized I put this in the Archive. Whoops!

            Here is another close up. It seems to be doing it NA too.

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            • #7
              Could you post the MSQ as well? This will help me tell if it's settings or something else.
              Matt at DIYAutoTune.com
              My PM box fills up fast - it's much better to email me at websales@diyautotune.com

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              • #8
                Originally posted by Matt Cramer View Post
                Could you post the MSQ as well? This will help me tell if it's settings or something else.
                HERE YA GO!

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                • #9
                  Somehow the MSQ file came through scrambled. What MegaTune version are you using?

                  I don't see anything weird happening on the data log other than what looks like some sort of misfire. Do you have a copy of the data log this picture is from:



                  I couldn't find that point in the log you posted. And the pictures don't have near the information I can pull out of a data log.
                  Matt at DIYAutoTune.com
                  My PM box fills up fast - it's much better to email me at websales@diyautotune.com

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                  • #10
                    where is your afr what are they when we know this we can help more im still saying your running to rich making ti hard for the spark to burn makiing it miss also matt is the coolent temp act liek that mine looked like that when it broke after i got a new gm coolent sensor the line has alitle smoother then that
                    Last edited by lthomas2g; February 23, 2009, 09:37 AM.
                    http://valid.canardpc.com/cache/banner/2653387.png

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                    • #11
                      Originally posted by lthomas2g View Post
                      where is your afr
                      I will get the wideband hooked up this week. I broke my hand and I'm not going to be able to put a post-turbo bung in for a little while, but I could probably put it in the primaries and get a less acurate reading. (low boost).

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                      • #12
                        yea that would slow things downs..think it would be much to take it to a muffler shop and have them do it?
                        http://valid.canardpc.com/cache/banner/2653387.png

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