Ignition breaking down boost over 20psi

Discussion in 'Technical' started by minivan, Sep 17, 2013.

  1. minivan

    minivan Guinea Pig Test Monkey

    this if for all the high powered zeds out there that have had there car making big numbers for quite a period of time

    my zed has been running 24psi for about 5 years now and 25-30000km
    it used to be great, ignition system could keep up.. now once she gets really hot on the dyno, any back to back run causes the ignition system to break down and missfire erratically on the top half of the graph (4500-7500 rpm)
    (not badly like hitting limiter or anything.. just a really erratic power graph and the car feels like its hesitating to make more rpm)

    ive changed the plugs to a colder number and gapped em lower (to .8) but it didnt make any difference.. given that i was running a higher gap and hotter plugs tuning the car in 40 degree heat in the past im just assuming all of my 25 year old ignition is getting old and crap

    so ive wound the boost down to 20psi, power down to 450hp ATW and all seems well. but id like to wind the boost back up, and given im about to convert to E85 id like the ignition to be in tip top shape so i can run max boost

    PTU is under the nose panel is clean air, coil packs have never been replaced

    considering changing everything to CDI and not worrying about it again..

    have you guys had no dramas with the stock coils and PTU at high power levels for long periods, or has running the car hard eventually just worn everything out?
     
  2. rob260

    rob260 Administrator Staff Member

    I had the same problem on high boost on the dyno recently too. Put some new denso iridium at .6mm and all good for now but will be fitting an HKS ignition amp at some stage
     
  3. MagicMike

    MagicMike Moderator Staff Member

    Any issues running small gaps at low loads? Incomplete burn? etc
     
  4. rob260

    rob260 Administrator Staff Member

    So far so good -ran great in the last cruise running low boost and cruising rpm most of the day, good economy etc too. It's still a bandaid in my opinion but for now it works.
     
  5. pmack

    pmack Member

    I run 17 thou plug gaps on mine , it was starting to blow the spark out (stock ign)
     
  6. MagicMike

    MagicMike Moderator Staff Member

    What's that in new world speak? lol
     
  7. Z32 TT

    Z32 TT Active Member

    damn. I thought our stock ignition was ok.... can you use LS2 coils or something?
     
  8. Chilledpain

    Chilledpain Z Reaper

    Bout 0.43 or just over I believe
     
  9. rob260

    rob260 Administrator Staff Member

    That's what I got too -assuming its 4.3mm?
     
  10. rob260

    rob260 Administrator Staff Member

    I don't think stock system is bad as such, just a case of shit happens when you push the limits...
     
  11. MagicMike

    MagicMike Moderator Staff Member

    4.3mm is a pretty big plug gap lol
     
  12. rob260

    rob260 Administrator Staff Member

    Ha oh yeah -derp haha
     
  13. WazTTed

    WazTTed Grease Monkey

    i run 0.7 i had identical issues over 20psi even with running a hks ignition amp..

    need to drop your plug gap to 0.6 for over 20 psi ...
    also what plugs

    bkr6es
    bkr7es

    im trialling
    bkr6ey at the moment that are frikken scary good ( V groove large electrode)
    boosts off like a mofo and doesnt missfire at idle or low load as the V groove helps burn off any deposits on the plugs !! havent tried over 20 psi on them tho .. thats brown pants city on the open road :br::br::br::br:
     
  14. bRACKET

    bRACKET Do Right Dean

    Did you find much difference with the hks amp? Currently running it now?
     
  15. andy

    andy Member

    If you have been using the same brand and heat range plug with the same gap for the last five years without a problem then a new set of the same plug with the same gap should rule out plugs.

    If the problem is consistently only after a couple of runs on the dyno and has only just started happening then it would appear to be a heat related electrical fault.

    You could try monitoring the temperature of the coil packs and PTU with a IR heat gun and see at what temperate the misfire starts. Then cool the coil packs or PTU and see if it fixes the problem.
     
  16. aazn

    aazn New Member

    im going out on a limb here... the new battery you installed... does that give out enough power to run your car on full boost?

    try putting a bigger battery in it for a few tests (tests on dyno)

    i remember my sti having the same problem. (old battery.) put in a bigger one and problem went away.. just going out on a limb...
     
  17. minivan

    minivan Guinea Pig Test Monkey

    bonus points for paying attention!

    but yes it does sadly.. voltage drop was one thing i was considering.. so i displayed it on the dash while doing runs. (i actually suspected alternator not battery) but it was rock solid at 14.4

    i used to run an old super cheap auto battery that was dead and had to be jump started most of the time

     
  18. WhiteNight

    WhiteNight Littering and...

    The circuit sports ignition amp is the same but cheaper alternative to the hks one. Works just the same.
     
  19. WazTTed

    WazTTed Grease Monkey

    Time for some ls2 truck. Coils :) apparently Z1 and a few other mobs are developing plug in kits
     
  20. minivan

    minivan Guinea Pig Test Monkey

    i was thinking these

    [​IMG]


     

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