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Thread: 1jz: cold start tuning

  1. #1
    BK Grease Monkey bk_'s Avatar
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    Default 1jz: cold start tuning

    I'm having cold start problems with the tune on the aftermarket ECU and would like input / suggestions on what may be the problem wrt tune.

    Initial maps were based on default PowerFC for 1JZ-GTE (eg: injector dead time, and crank injection).

    Stock injectors and stock twins on the 1JZ-GTE.

    Observations / logging:

    1) at 11C ECT on cranking, battery voltage drops between 9.1-9.6V, and struggles to start without using 30% throttle. Cranking injection is 39-40 mSec.

    2) at 19C ECT on cranking, battery voltage drops between 8.6-9.3V, starts a bit too quick, without using throttle. Cranking injection is 34.6 mSec.

    3) at 29C ECT on cranking, battery voltage drops between 9.2-9.6V, starts perfectly (within 3 cranks)! Cranking injection is 23.2 mSec

    4) at 39C ECT on cranking, battery voltage drops between 8.9-10.0V, starts slightly a bit too quick (within 1 crank?). Injection total on start is 19.7 mSec.

    5) at 49C ECT on cranking, battery voltage drops between 8.8-9.2V, starts very well. Crank injection is 15.0 mSec.

    6) at 81C ECT on cranking, battery voltage drops between 9.5-9.9V, starts very well (within 1 crank?). Cranking injection is 8.9 mSec.

    Any ideas or suggestions?
    Last edited by bk_; 14-07-2012 at 06:53 PM.

  2. #2
    Low rep Grease Monkey
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    Default Re: 1jz: cold start tuning

    thats a tough one dude

  3. #3
    :O Conversion King JZA70 R's Avatar
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    Default Re: 1jz: cold start tuning

    So is the issue at 11'c when the engine won't start without throttle assistance? Is the idle valve opening properly at that temp?

    Have you tried resetting the PFC to see how it behaves? If that fixes the problem you can slowly add back in your settings and maps until the issue repeats itself. Isolating the problem.
    JZA70|R / 12.45 @ 111 mph.

  4. #4
    BK Grease Monkey bk_'s Avatar
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    Default Re: 1jz: cold start tuning

    At 10C I know I reduced crank injection a bit too much. That was when I was experimenting with which direction to go.

    But when the engine has cooled down but is still warm (40-50C), that's when it also struggles to start (requires throttle). But when warming up from cold, 40-80C is OK (does not require throttle)

    I dont know whether I'm fighting a losing battle or not to perfect it.

  5. #5
    BK Grease Monkey bk_'s Avatar
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    Default Re: 1jz: cold start tuning

    Problem is now resolved.

    Tuning software can accept two sets of numbers for ignition coil charge: degrees (RPM) or time (msec).

    I entered the numbers in degrees from PowerFC, however the software / firmware stores it in time (msec).

    Unfortunately, I did not set the 0 RPM figure properly (it was ~5.1 msec instead of ~4.1 msec) and >= 4000 RPM was off by up to 15%, due to rescaling RPM the axis ~12 months ago, without checking if it was rescaled properly.

    Tried cold start (13C ECT / IAT) today, worked no problems. Tried 4 days ago, started first time, too.

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