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Thread: Quick question on 4BD1-T Timing

  1. 26th February 2012, 11:29 PM #1
    110Landy86
    110Landy86 is offline Master
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    Quick question on 4BD1-T Timing

    As the title suggest, is it recommended that timing be adjusted following fitting turbo to N/A engine? And if so is it better to have the timing slightly retarded or advanced for turbo.

    Also is the engine noisier with advanced timing.

    Thanks in advance (no pun intended) hah
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  2. 26th February 2012, 11:35 PM #2
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    Blknight.aus
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    you can wind it on a tiny bit not more than a degree or two but that depends on your initial timing settings.

    play it by ear and go gradually testing at each stage at full load/temp/and nominal RPMs (from memory the auto advance is fully wound in by 3200 RPM)
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  3. 27th February 2012, 09:03 AM #3
    Dougal
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    More retarded gives more exhaust energy to spool the turbo, more advanced gives crisper response and slightly better economy.

    I have tried the range of adjustment and found the factory marks to be the best compromise. Guess those Isuzu engineers got it right.
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  4. 27th February 2012, 07:33 PM #4
    C H T
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    110Landy86

    Pump timing for the 4B1 is as follows:

    4BD1 13 degrees before top dead centre
    4BD1T 10 degrees before top dead centre

    Note the timing of a factory turbo engine is 3 degrees retarded when compared to a naturally aspirated 4BD1.

    Most 4BD1s that I know of which have had turbos fitted to them have not had their pump timing altered, and go well.

    My advice would be to stick with original pump timimg when fitting a turbo to a 4BD1.

    FWIW

    C H T
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