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Crank ISC duty cycle

Discussion in 'Tuning À la carte' started by CJK440, May 3, 2016.

  1. CJK440

    CJK440 Active Member Established Member

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    Copying over the BSK cells to MBT (reduced the values) killed the flare. So much that I had to go put the ISC Duty cycle table back to stock to get it to start.
     
  2. 03Steve

    03Steve Active Member Established Member

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    There you go.
     
  3. 04torchred

    04torchred Well-Known Member Established Member

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    Sorry to dig this old thread up, but I am having a very similar issue on start up. Car has the TPS set to 0.9 volts(key on engine off), throttle blade has been opened up to allow the IAC duty cycle to be around 0.26-0.3 when warm. Car idles well at 800-850rpm when at operating temp.

    But same problem as original poster. Cold start it fires up and then dies unless I add throttle input. Same thing happens with a restart if I shut the car down between 60*F up to around 150*F. It fires, flares up to 2000rpm and then rpms fall and it dies unless I stab the throttle a bit. Then it revs up again and steadies out on its own and idles just fine.

    So far I have zero'd out the base fuel table cold enrichment decay time table. Seemed to have helped some as I dont need to pedal input as much to get it to steady out.

    I just found this thread so I am going to try logging the spark source tonight and see what I can find.

    Any thing you can share on what finally ironed out your tune would be great. This same setup with a smaller MAF (JLT 110mm, now has a 123mm crusher MAF) has started fine with a tune from Lund Racing so I must just be missing something on my tune. WOT fueling is good, I just have an ever so slight part throttle stumble at low rpms when you stab the gas a bit, but I am sure I just need to mess with some transient fueling after. That issue only seems to happen on the first stab, don't notice it if you stab again quickly.
     
  4. 03cobra#2

    03cobra#2 Hobbyist Of Many Hobbies Established Member

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    Just some ideas: the crank isc is during start up, so that's the initial start / fire up. I would look at a table that adds additional rpm at start up. Also make sure you are not going right into closed loop to give your 02's time to heat up. Just some ideas.

    Sent from my Pixel 2 XL using Tapatalk
     
  5. 04torchred

    04torchred Well-Known Member Established Member

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    From 3 logs I grabbed yesterday it appears to hold a nice start and idle following the start if I am remaining on idle source 9. When it switches to idle source 1 my rpms immediately fall and the idle starts to surge or stall.

    When its in idle source 9 its holding around 15 degrees as its warming up and then between 18-21 degrees of timing as a range. As soon as it hits spark source 1 it drops to spark as low as 5 at times.

    My open loop flag field appears to just stay on zero which seems wrong. The Open loop timer is giving me a value, one log had 63 seconds.

    Wideband A/F on the cold start is showing mid 10's to mid 11's.

    Seems like the spark is some of my issue with it not wanting to stay running.

    In livelink it shows the spark source values, but does anyone know what tables those actually reference in PRP?

    I don't know what Spark Source 9 is - Idle Feedback (is this your MBT table or Borderline?)
    Spark Source 1 - Base (none of the values in my borderline table or MBT spark go this low at the load ranges I am showing at idle)

    More info. My Throttle position absolute at idle is 169, at a coolant temp of 76*F its showing Idle air duty cycle at 0.60 and integrator is calling for varying amounts(0.05 up to 0.23)
     

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