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Thread: Help me tune my timing

  1. #1

    Default Help me tune my timing

    I just added timing control and I need help tuning my curve. I drove it for the first time and it did ok. Kind of had a surge when I stabbed the throttle and didn't pull quite as hard is it did without timing control. Tip in was ok but not great, it did stumble a tad. WB02 also threw an H error code. Here's my setup:



    Chevy 355

    Vortec heads

    Lunati cam 489/504 lift, 227/233 duration @50

    10:1 compression

    3.73 posi rear end

    4 speed manual trans



    IAC - 29 at operating temp (should be lower 10-15ish or less)

    Power Valve - 17%

    Pump Squirt - 30%

    A/F ratios: idle 14, cruise 14, WOT 12

    Idle target: 900rpm



    Ignition Timing:

    Idle RPM - 1000

    Total RPM - 3000

    Idle ADVANCE - 12 degrees

    Total ADVANCE - 32 degrees

    Vacuum advance - unported 10 degrees



    Any help would be great. Thanks



  2. #2

    Default Help me tune my timing

    Looks pretty close to me. I might pull a bit of PV out, maybe closer to 12 and the PS might push to 35 or closer to 40 if it needs it.

    You didn't list the rest of your settings and they may have an impact on our suggestions.

    I might also bring timing in a bit faster and be all in at around 2500-2800

    Post up the rest and let's see what you're doing.

  3. #3

    Default Help me tune my timing

    Ok here you go, I think this is all of it..



    IAC 29ish warm (I think we have part of the mix here, should be lower)

    MAP 15

    TPS 0

    IAT 128

    Fuel Pressure 38





    Thanks as always fcsallan. I'll modify the timing as you recommended and any other suggestions you can make. Also, should my idle rpm (1000) be closer to my target idle (900)?

  4. #4

    Default Help me tune my timing

    Ok I made the recommended adjustments and adjusted the iac down. Major improvement. Tip in still has a very slight stumble but not bad (may be my clutch skills at this point). I'm still getting a surge at higher rpms (3-6K). Is it possible I have too much PS and need to go the other way?



    Total advance dropped to 2500rpm

    IAC 0

    PV 13

    PS 35



    On a side note, I noticed the connection between the mag pickup from the throttle body and the distributor is very finicky. I bumped it while adjusting things under the hood and the car shut off and wouldn't start. After jiggling the wire it fired right back up. The connection at the pigtail is tight, I wonder if the wires inside the connector are having problems?

  5. #5

    Default Help me tune my timing

    I would certainly chase a bad wiring issue, they tend to come back to you when you don't have time to fight it.

    As for the PS, I would say this is not your issue. Pump squirt adds fuel at tip in, PV adds throughout the band. If it is surging you may have to tweak that setting a bit. Try a bit lower and see if it gets better or worse, obviously go the other way if it gets worse.

    On a side note, the surge could also be related to not enough fuel. I personally would push the fuel pressure to 40-45.

  6. #6

    Default Help me tune my timing

    Ok I believe I've fixed the wiring connection. I had to replace that pigtail a while back and I believe it was loose. I took it apart and made a tighter fit with the wire.



    I'll make another adjustment to the PV and PS and see what happens.



    I'm running the fuel system returnless. How do I adjust fuel pressure??




  7. #7

    Default Help me tune my timing

    You set the pressure on the handheld.

  8. #8

    Default Help me tune my timing

    Pardon my ignorance. I don't see an option anywhere on the handheld to adjust fuel pressure. Which screen is it under and how is it labeled? I do have the latest firmware updates.




  9. #9

    Default Help me tune my timing

    You are correct, sorry, I don't know why I was thinking that it was adjustable. I suspect the PWM is adjusted by the computer. I have had return with regulator too long.

  10. #10

    Default Help me tune my timing

    Gotcha. Well first things first. It ran without a stumble with the HEI setup, I believe we'll figure it out with a little trial and error. It did get better with the adjustments made yesterday. Down the road I may try adding the return with a regulator, it's just not in the budget right now.



    I may make the total timing 34 degrees instead of 32 and see how it likes it. Should I back out a little vac advance or should it be ok at 10 deg? I'll chime back in when I get a chance

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