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Thread: Spark advance tables

  1. #1
    Fuel Injected! myredprky's Avatar
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    Cool Spark advance tables

    Help ??????? Can anyone please expalain why with a carb and dizzy setup the ignition timing will go to around 32-36 deg of total advance with a wide open throttle but with tpi (1227730 ecm) the total advance when the kpa values rise is taken down to around 20 deg???? .I am mapping out my ve tables but have noticed that the power drops off as the timming drops off,I have more power by lifting the throttle and bringing down the kpa,s.....?

    engine is
    350 sbc
    with Edelbrock heads
    10-1 compression
    comp cams with 220\230\@50
    Accel manifold base
    ASM runners and ported plenum
    Headman hedders
    and 52mm throttle body.

    I am hopping to get around 400hp from this setup (would that seem right to you guys)
    Do I need to give it a lot more timing at the top end of the kpa vs spark map ????

    many thanks IAN....

  2. #2
    Fuel Injected! gregs78cam's Avatar
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    From that short parts list I would say 400hp sounds very possible from this setup. And as long as you have a good functioning knock sensor in it, sure, add some timing and see what it likes.
    1978 Camaro Type LT, 383, Dual TBI, '7427, 4L80E
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  3. #3
    EFI GearHead ! EagleMark's Avatar
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    Stock OEM carb and distributor curves were close to EFI for idle and acceleration. Just like a carb and dizzy setup with built motor you can add timing.

    Just sneak up on max timing. There are so many varibles in ECM/Chip and EAT module that your Main Spark Advance will probably not be actual! Check timing with timing light at timing marks at various RPM and see where your timing really is compared to bin or ALDL spark timing data if you have it. Totally warmed up, 3000 RPM and pinch MAP line to cause 100 MAP, get timing, is a good test.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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  4. #4
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    I too would be interested in opinions on the question. As OP said, in early days full throttle 36 degrees, no knock sensor and all was good. Now with efi any time you get rpm and load the timing is 20 degrees and less. Are they worried about making too much power? Are they worried about their warranties? Are they worried about weak transmissions? What do you think the answer is?

  5. #5
    EFI GearHead ! EagleMark's Avatar
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    Emissions.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  6. #6
    Fuel Injected! myredprky's Avatar
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    Thanks guys,,just made a vast improvement by looking into my Enrich Power Spark Advance Vs. RPM table to find it had all been zerod out.I copied over the tables from an super AUJP bin and thats made a big differance in pulling power...But I rekon I should be looking for 32 full advance in wot at 3000 rpm on but my spark map just wont allow it....
    the spark table I have is shown below.....
    Attachment 2881

    should I be going for somthing like this in the 100 kpa range.....?????

    IMG_1857.jpg
    Last edited by myredprky; 08-19-2012 at 11:59 AM.

  7. #7
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    part of the reason you see a lot less advance is due to better head/combustion chamber design. better heads need less advance to make their peak power, going beyond that point will actually cause a drop in power, followed by detonation.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  8. #8
    Fuel Injected! PJG1173's Avatar
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    remember total advance for a carb setup is base timing + vacuum adv + mechanical adv (10+10+16=36). At WOT you should be at 0 vac so your timing would be just base + mechanical (10+16=26). It took me a while to wrap my head around how the timing table mimicks how I used to set carbed motors up for.
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  9. #9
    EFI GearHead ! EagleMark's Avatar
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    Quote Originally Posted by PJG1173 View Post
    remember total advance for a carb setup is base timing + vacuum adv + mechanical adv (10+10+16=36). At WOT you should be at 0 vac so your timing would be just base + mechanical (10+16=26). It took me a while to wrap my head around how the timing table mimicks how I used to set carbed motors up for.
    When timing a race motor no vacuum advance/retard. Timing tape on harmonic balencer and set timing to 33ish at distributor max advance.

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  10. #10
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    well, race engines generally spend all of their time at 0 vacuum or idle, and idle isn't much of a priority, so that makes sense.
    1995 Chevrolet Monte Carlo LS 3100 + 4T60E


  11. #11
    Fuel Injected! myredprky's Avatar
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    Thanks guys,,I have increased the timming a little and it realy has made a differance (its up to about 28 before now at 4800 rpm ----)Time to redatalog the ve tables again now...

    I will post some pics of this classic Range Rover up later today..

    Cheers IAN..

  12. #12
    EFI GearHead ! EagleMark's Avatar
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    And you have verified timing with a timing light right? Just because it says 28 in spark table does not mean it's 28 at timing marks!

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
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  13. #13
    Fuel Injected! myredprky's Avatar
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    The only timing I have done at the mo is is to the power enrichment mode as the timing here was all zeroed out so I copied this over from the AUJP bin....

  14. #14
    Fuel Injected! myredprky's Avatar
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    Just a quick one,,but does anyone have or know what injector offsets i should be using with Bosch 0280159785 orange top 30lb injectors with tunerpro rt.?????

    cheers IAN

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