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Thread: 6530 Run Retard Curve Help

  1. #31

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    Hello, I'm just setting up and have a question when it comes to setting the advance. Do I get the car started let it idle and set it to 32 deg at idle and lock it down?

    I want like 7 deg at startup and all in at 32 deg around 2800 rpm. Thanks.

  2. #32

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    Quote Originally Posted by Murray2rude View Post
    Hello, I'm just setting up and have a question when it comes to setting the advance. Do I get the car started let it idle and set it to 32 deg at idle and lock it down?

    I want like 7 deg at startup and all in at 32 deg around 2800 rpm.

    Thanks.
    Yes that's how you will set it. You will need to set it at 32 degrees than in the run retard curve you will set it up to pull the timing at the lower RPM and build your curve to get all your timing back in at 2800.

  3. #33

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    Hello, I think I have the timming all set i want 15 cranking and 10 idel max at 32 deg. I'm now playing with a 1 bar map sensor and want to know if my maps look ok? The motor is a 1915 vw motor with dual 44 webers.

    I have read and read about setting this up but I'm still kinda scratching my head. Any help is appreciated. Tom m.20180916_122623.jpg20180916_122623.jpg

  4. #34

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    Quote Originally Posted by Murray2rude View Post
    Hello, I think I have the timming all set i want 15 cranking and 10 idel max at 32 deg. I'm now playing with a 1 bar map sensor and want to know if my maps look ok? The motor is a 1915 vw motor with dual 44 webers.

    I have read and read about setting this up but I'm still kinda scratching my head. Any help is appreciated. Tom m.Attachment 4597Attachment 4597
    Any help please.

  5. #35

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    Can someone please confirm: On the 1 bar MAP I show the red line at 14, so does my first dot start there and I work my way to the left to say 10° to add that to my total timing at cruising speeds?

  6. #36
    Join Date
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    Sacramento, CA
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    Quote Originally Posted by Murray2rude View Post
    Can someone please confirm: On the 1 bar MAP I show the red line at 14, so does my first dot start there and I work my way to the left to say 10° to add that to my total timing at cruising speeds?
    You're not adding, you're taking away timing if you do that. With your current graphs I think you are pulling out 24° away from the 32° at idle so your actual timing is 8°, (21° on the top curve, plus an additional 3ish on the bottom graph).
    I'm new to this too, and hope you get your answer. I will try to help and share what I think might help. To convert the numbers on the top of the Boost Retard Curve to vacuum, you take:
    (15 - 0.00) x 2 = 30 inHg
    (15 - 2.00) x 2 = 26 inHg
    (15 - 4.00) x 2 = 22 inHg
    (15 - 6.00) x 2 = 18 inHg This is probably as much vacuum as you will see.
    (15 - 8.00) x 2 = 14 inHg
    (15 - 10.00) x 2 = 10 inHg
    (15 - 12.00) x 2 = 6 inHg

    I realize this is not what you asked specifically, but I'm trying to get you there. Write the vacuum numbers across the top to think in vacuum terms that may help you conceptualize what is happening. Vacuum increases to the left but you should not be pulling degrees out in this left section of the graph since your engine wants more timing at higher vacuum instead of less, and this MSD curve is pulling out IE retarding your timing if you plot big numbers on the left side. You want your curve starting high on the left and sloping down on the right, opposite of what you did.
    Last edited by gregski; 01-09-2019 at 09:09 AM.

  7. #37
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
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    I couldn't find a table on the net, so I made my own. This table is PSIA to vacuum as measured in the inlet manifold.

    PSIA inHg
    0 - 30
    1 - 28
    2 - 26
    3 - 24
    4 - 22
    5 - 20
    6 - 18
    7 - 16
    8 - 14
    9 - 12
    10- 10
    11- 8
    12- 6
    13- 4
    14- 2
    15- 0

    So on your boost retard curve, if I want timing to start retarding at 8 inches of vacuum, 11 PSIA is the figure to start at.

    Of course, if you want 7 inches of manifold vac, you can work it out from the table.

    Your line should start at the left on the 0,0 point go across the right to the point where you want the timing to start to retard, then down to right to where you want all the "advance" out, say 13 PSIA, then across to right to 15 PSIA.

    The amount of "advance" here is a retard just like the run curve.

    So when the two curves are combined, ignition timing needs to account for the map sensor connected.

    Both curves retard timing, that's why the boost retard curve goes down as you approach 14 PSIA.

    Map pressure of 0 (zero) is a pure vacuum. MAP, Manifold Absolute Pressure. Gary
    Last edited by Gaz64; 01-09-2019 at 10:35 PM.
    Regards, Gary

  8. #38

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    Hello and thank you for the information. I've corrected both maps to account for the boost retard curve. It makes sense now that I know how the map works with the timing map. Now I just have to take the car out and see how it likes it. Thank you again. Will probably post my map once I try it out.

  9. #39
    Join Date
    Jan 2010
    Location
    Brisbane, Australia
    Posts
    1,296

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    You're welcome Murray. Come back with your results. Gary
    Regards, Gary

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