how to advance timing?
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  1. #1
    Member bj_dove's Avatar
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    Default how to advance timing?

    g'day,

    ive just been doing some pondering about my proposed turbo setup on the mi16, and i couldnt think how i will advance the timing on the ignition when i come to tune it, considering it has a single coil and a distributer, how do i go about doing this? obviously it must be possible, but how?

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    cheers
    '91 Peugeot 405 Mi16 - only just run in......

  2. #2
    1000+ Posts PeterT's Avatar
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    It's impossible with the std. Motronic ECU. All timing is calculated by the ECU, which gets its initial signal approx. 60 deg BTDC from the crank sensor. You need to upgrade to a programmable ECU. I thought it was more usual to retard the timing when it comes on boost.

    '92 205 Mi16
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  3. #3
    Member 750sport's Avatar
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    You will likely need to remove atleast 10 degrees of advance for 4-5psi boosted system.

    A piggy back ecu like emanage\link etc will allow you to run larger injectors (no 5th injector or rising rate fuel pressure regulator) to control AF ratio and they can manage advance curve as required.

  4. #4
    1000+ Posts HONG KONG PUGGY's Avatar
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    Quote Originally Posted by bj_dove
    g'day,

    ive just been doing some pondering about my proposed turbo setup on the mi16, and i couldnt think how i will advance the timing on the ignition when i come to tune it, considering it has a single coil and a distributer, how do i go about doing this? obviously it must be possible, but how?

    cheers
    Hi bj_dove,
    Timing settings would be unique to specific management systems. I can only speak form personal experience, but my Saab 9000 turbo is set to 16* BTDC initial setting.(0.75 - 0.9 bar)I have seen some modified cars run more, it all depenends on what engine management you choose. Another factor is the compression ratio, and low speed drivability: if you want low down torque before boost comes on full, you have to up the comp ratio, and therefore timing could be a little closer to standard.
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  5. #5
    Member bj_dove's Avatar
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    sorry to revive an old thread, but i havent had much time lately!

    i am upgrading to an aftermarket ecu, either a piggyback style one, the SMT6 from www.perfectpower.com, has my attention, or a microtech or similar.

    what my small brain it struggling with is that how the 1.9 has a distributer, and so the rotor spins round inside the cap and distributes the spark to each plug, right? i would have thought that this is a physical setup and so the timing cant be changed electronically? please help me understand!

    cheers
    '91 Peugeot 405 Mi16 - only just run in......

  6. #6
    Member 750sport's Avatar
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    The rotor inside the cap is wide enough that the spark will jump the gap over 10-15 degrees of rotation (20-30 degrees of crankshaft), so the spark timing is done electonically and just jumps the gap, saving the cost of 1 coil (wasted spark) or 3 coils for the manufacturer.

    You need timing and fueling control to allow for tuning when adding a turbo\supercharger. Aftermarket piggyback\standalone ecu is the only reliable option if you are chasing 5psi+

  7. #7
    1000+ Posts PeterT's Avatar
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    Quote Originally Posted by bj_dove

    what my small brain it struggling with is that how the 1.9 has a distributer, and so the rotor spins round inside the cap and distributes the spark to each plug, right? i would have thought that this is a physical setup and so the timing cant be changed electronically? please help me understand!

    cheers
    That's correct, the dizzy cap is fixed to the head and the rotor button is fixed to the cam. So it can't be adjusted mechanically.

    The TDC sensor fires for arguements sake at say 60 deg. BTDC. This gives the ECU time to DELAY the spark so it occurs somewhere between 10 and 30 deg. BTDC. All aftermarket systems work the same way, although you can normally alter that initial timing point between 60 and 100 deg. BTDC to cater for different sensor setups. This point is fine tuned with software so you get an exact timing figure, which can be verified with a timing light.

    The Haltech software for example, has a function which locks the timing at 10 deg. BTDC. You then check with your timing light to verify this is correct. If it was 5 deg. out, you would alter the initial timing point from say 75 to 70 deg. in the software setup, then recheck. Once this is established, you unlock the timing and start tuning.

    Remember that when you adjust a conventional dizzy, you're altering the low tension event. The high tension event can occur over a much wider arc.
    Last edited by PeterT; 18th January 2005 at 03:07 PM.

    '92 205 Mi16
    '90 Mi16x4

  8. #8
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    mistareno's Avatar
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    As has been discussed, the distributor has no advance mechanism and is simply a HT spark distributor.

    What no one has discussed, is the possibilty of simply moving the ignition pick up a few degrees in a clockwise direction.

    This will then give the computer it's firing signal slightly later than normal, effectively retarding the timing by the same value over the entire engine range...

    If all you need is a few degrees retardation this won't result in any adverse affects but will allow you to keep the standard computer and wiring loom (which you may be able to reuse regardless).

    It may not produce absolute optimal power but it will save you big dollars and if you're only running conservative boost it might be fine...

    Just some food for thought...

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