Detonation

Discussion in 'PSI Superchargers Tech Questions' started by bruce boland, May 23, 2016.

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  1. Critical Mass

    Critical Mass Member

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    Hi Bruce,
    Do you have a data logger? If so what does your rpm curve look like?
    Did it have sharp spikes on it?
    Thanks, Joe
     
    #21
    Critical Mass, May 27, 2016
  2. bruce boland

    bruce boland Member

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    Hi Joe
    At about 1000 ft the graph spikes a lot , I was thinking it was the plugs with a huge gap.up to 1000 ft it looks good
     
    #22
    bruce boland, May 27, 2016
  3. Critical Mass

    Critical Mass Member

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    Hi Bruce,
    After reading your post I now believe I might of had the same thing happen to me last year. I have just about the same set up as you do: 44 mag, 14-71 at ~20# of boost.
    On my last "pass" #7 rod broke at the tree, it knock off the head of the intake valve, ground off the piston skirt up to the oil ring and then exited the block through the pan rail.
    I found it strange that the porcelain on my #7 plug shattered but the ground strap didn't close up the gap. Up until your post, I assumed all the carnage was due to the rod breaking. However, I could never figure out what caused the RPM spikes from the data on two previous passes.
    I also run a crank trigger, Leahy 3/8", with the ground strap connected to battery ground at the block. The crank trigger might have picked up some RF from the loose plug wires. It looks like I need to prevent them from flopping around in the future.
    Well it's all history now but it would be nice know what really caused the mess, so we can address it for our next build!
    Good luck, Joe
     
    #23
    Critical Mass, May 28, 2016
  4. bruce boland

    bruce boland Member

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    Thanks Joe,
    I would have thought the same thing because by the looks of #1 rod bearing and pin end I think the rods would have come out in a couple more runs, I think no grounds on the heads and coil wire zipped together along with the crank trigger harness may have caused some problems also,
    Another thing I found this morning is under the MSD cover for the wires I had 3 wires crisscrossing each other with #2 under #5 over and #1 in the middle, Those are my 3 bad cylinders with #1 the worst,
    Never stop learning with these things,
     
    #24
    bruce boland, May 28, 2016
  5. rb0804

    rb0804 Active Member

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    Are the rpm spikes you guys seeing up spikes or down spikes?
     
    #25
    rb0804, May 28, 2016
  6. bruce boland

    bruce boland Member

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    Spikes are all up, they start at around 5 seconds . Up till then a smooth graph.
     
    #26
    bruce boland, May 28, 2016
  7. Mike Canter

    Mike Canter Top Dragster
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    Here is a little background on random firing ignition systems caused by crank trigger interference. Back in the 1990's we were having big time problems in nitrous motors which was destroying pistons and rods. We were using the MSD 7AL2 and the 7AL3 systems with crank triggers. The ignition box was normally located inside the car so we used long wire cables from the trigger to the ignition box. We would swear that the ignition box would stop retarding the timing when nitrous stages came on causing massive detonation. We would send the MSD box to MSD for repair and it would come back saying nothing wrong with it. Put is back on the car and would destroy the motor again. A lot of racers switched to Mallory systems and stopped having problems. I got to be a friend of the MSD back room guys and learned about this random triggering of the ignition and that it can be caused by the high voltage spark, the electric water pump or even the electric radiator fan. When I talked to the MSD back room guys they told me that I should use their special shielded crank trigger cable and ground the shield. All the problems went away just like magic and we all learned to route this shielded cable away from anything that could cause interference. Occasionally we see this problem return if the crank trigger is routed too close to the coil or plug wires.
     
    #27
    Mike Canter, May 28, 2016
  8. jay70cuda

    jay70cuda Well-Known Member

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    Sounds like a command module would fix your problems. If top and funny car make it work fine then my lousy 2500hp car should be just fine with it.
     
    #28
    jay70cuda, May 29, 2016
  9. Mike Canter

    Mike Canter Top Dragster
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    the problem is not the Grid. The problem is the low amplitude signal from the crank trigger sensor. Even with the Command Module you would still have the same problem
     
    #29
    Mike Canter, May 29, 2016
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