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Thread: Backfire through Intake manifold Cold only Speed Density

  1. #1
    Potential Tuner
    Join Date
    Oct 2018

    Backfire through Intake manifold Cold only Speed Density

    Alright so before I go on its a Gen 4 engine with a Lingenfelter 58 to 24 conversion box P01 red and blue.
    The mods
    car is 1987 Mazda rx7
    2008 4.8 out of a Suburban
    Speed density
    80lbs deka e85
    80mm VS turbo it works great for my setup
    Comp custom grind 5710586 116 281/238
    btr dual valve springs stock length push rods.
    arp head bolts
    ls3 front cover with a 4x cam gear.
    Stage 3 2004r (tighter) 3k on foot 3800 flash stall non lock its controlled by a tv cable as why i have it as manual. (NO SPEEDO sorry)

    The Issue i have is, I have hard cold starts, backfiring through intake once started when i stab the go go pedal. Leans out on like acceleration tries to stall. When i give it gas it will go lean and tries to die. But if i shut it off and start it a few time it will get better. I have replaced the Cam sensor with a new one and it made no difference in the situation. I have posted a log and my tune. If anyone can give me a thought or direction please let me know i would be greatful.

    Things i have changed.
    I have also tried messing with the Fuel on wall and the impact with no help actually made it worse. My injector open rate normal and make up. Ive tried richening up my kpa from 60kpa up to 100kpa at idle and up to around 3k. This helped once warm but not cold. I am newer to HP but not to tuning. Kinda wish there was a accel enrichment. If there is i have not found it hahah
    Attached Files Attached Files
    Last edited by Holcomb_Matt; 6 Days Ago at 07:30 PM.

  2. #2
    Tuning Addict 5FDP's Avatar
    Join Date
    May 2012
    Rogers, MN
    Why do you have the timing swinging 40 degrees??

    The over/under speed spark correction should be like less than 10 for a cam that size.

    Do you live in the mountains? The MAP kpa when not running makes it seem that way, or the data is wrong for the sensor.

    I'd zero out the negative timing pull that the ECT spark correction table can do at cold starts. This way it follows your idle timing and high/low tables without pulling 8 degrees out.

    Have you been tuning the VE with a wideband using and AFR or Lambda error to help correct your fueling?
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

  3. #3
    Potential Tuner
    Join Date
    Oct 2018
    The cam swing honestly was me reading through old threads on here and one of the Hp main guys said to do that to get more loppy cam sound. I was just trying it out I know its excessive right now. But it has been doing the backfiring before I even changed that.

    I do live in high altitude Denver Colorado 5280 above sea level. So my zero is about 80kpa give or take

    As for my wideband yes I use a AEM gauge and do the have over want equation because I have the mvpi2 and do not have the pro feature Wish I did life would be simpler haha.

  4. #4
    Senior Tuner Ben Charles's Avatar
    Join Date
    Aug 2009
    I’m guessing your issue is with the conversion box.. seen same problem many times

    Email Tunes, PM me for more info
    96 TA Blown/Stroked, 4L80E/Fab 9
    15 C7 A8 H/C 2.3 Blower/PI
    14 Gen 5 Viper
    Custom Mid Engine chassis, AKA GalBen C

  5. #5
    Potential Tuner
    Join Date
    Oct 2018
    That would suck.