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Cold Start Log

Discussion in 'FAST Support Forum' started by wabco40, Sep 3, 2017.

  1. wabco40

    wabco40 New Member

    Joined:
    Nov 13, 2015
    Location:
    Perth, Australia
    Hi, I just have a few questions on cold start tuning.

    When I first start to crank the engine there is a 1500 rpm spike. What would be causing this? Could it possibly be interference?
    Also how long should I have the afterstart enrichment happening considering there is warm up enrichment (this is all out at 136 F).

    I'm also using 0 to 12 degrees of timing trim as can be seen with the erratic spark in the log. Would using this much timing trim be ok or should I look at making this lower?

    any other suggestions would be much appreciated.

    I'm using XFI 2.05 and the engine is a 427 SBC with 42lb injectors and Comp Cams 280XFI HR13 (Duration @.050, intake 230, exhaust 236 and 113 LSA).

    Attached is a short log.

    Thanks
    Brad
     

    Attached Files:

  2. Fastmanefi

    Fastmanefi Active Member

    Joined:
    Jun 4, 2011
    Location:
    Sonora, CA
    1) The RPM spike at the beginning of cranking is a common problem, usually caused by the starter, but FAST has never focused on fixing that. I have isolated this problem using a separate battery for only the starter but there were still signs. You might just have to live with that.
    2) 12 degrees of timing trim is a lot. If you think about that you might be adding or subtracting a lot of trim to the base spark table. I would limit timing trim to 6 degrees.
    3) You can monitor the Actual AF ratio during warm up and adjust After Start and CTS warmup in real time trying to keep the Actual AF in the low 13s during the entire warmup cycle.
     
  3. wabco40

    wabco40 New Member

    Joined:
    Nov 13, 2015
    Location:
    Perth, Australia
    Cool, thanks for that.
    I guess I'll just live with the spike.
    I read in a previous post to set the timing trim from 0 on the left to 12 on the right. I thought it might be a bit much, I will max out at 6 and see how that goes.
    The warm up cycle is currently in the low to mid 12s so will do as you suggested and adjust to the low 13s.

    Thanks for the reply.

    Brad
     

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