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Thread: 123 Tune+ ignition curve for 2.0S

  1. #11
    This is very familiar page to me and very good source of information regarding ignition curves. I might be wrong, but this is how I read it:

    The way I read it is, that the curves and values are presented as dynamic advance given by distributor excluding the static (initial) advance. That is logical as static advance is basically the only easy way to do adjustment in mechanical distributor and moves the complete curve. The text explanation says:

    "Advance for 159 002 starts at about 500RPM at the distributor (and 1000RPM at the crank)..."
    So at idle total advance equals initial advance as dynamic advance from distributor is 0, so total advance seen by engine at idle is initial 8 BTDC + 0 = 8 BTDC.

    "and advances toward about 8.5" at about 900RPM... Advance remains steady until 2400RPM"

    given the notation used in text both of these values refer to distributor values, this can be confirmed from the graph also. So it would be 17" 1800RPM engine speed. Total advance seen by the engine would be 17+8=25 degrees. Distributor advance remains steady until 2400RPM (4800RPM at engine)

    So the total advance seen by the engine between 1800-4800 RPM engine speed is 25".

    "where it increases again toward 11.5" at distributor (23" at the crank) and levelling out 3400RPM (6800 RPM at the crank)."


    So from 4800-6800RPM advance ramp goes up reaching total advance 23+8=31 at 6800RPM engine speed. This last part is bit contradicting the instructions that total advance should be set 30-31 at 6000, but I presume it is there to have margin in adjustment. Anyway the total advance should be below 37 all times.

    My initial curve is fairly close to those values if initial advance is taken in the account and engine + distributor set to 0. Again, I might be wrong but this is how I deducted it.

    Br,
    Aki

    Quote Originally Posted by NorthernThrux View Post
    From http://www.sparkingplugs.com/9.html
    My service manual and everything I have read says advance at idle (static) should be 5-10 degrees so that total advance at 6800 rpm is under 35 degrees.

    Attachment 621157
    Last edited by prea; 07-10-2024 at 03:54 AM.

  2. #12
    Senior Member NorthernThrux's Avatar
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    Yes, this is my interpretation too. As long as your timing values sit within the factory range I posted earlier from the service manual (which are advance values - you need to add the static to them), you have a good place to start.

    Timing isn't super sensitive. Many people have the vacuum advance fail on their distributors and never even notice that for the life of the car!

    You'll never really get an optimized curve unless you tune on a dyno. SO just set it to some nominal curve and forget it. That's why I just got the switched version. I really don't care if I am missing 2 or 3 hp somewhere along the curve in a 51 year old car!

    Ravi
    Early 911S Registry # 2395
    1973 Porsche 911S in ivory white 5sp MT
    2015 Porsche Macan S in agate grey 7sp PDK

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