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Thread: Help me tune my timing

  1. #21

    Default Help me tune my timing

    Well, if it liked 18, it might like 20 even more. Just watch out for preignition. I would at least try the mild cam setting, it costs nothing but a little time.

    Gerry

  2. #22

    Default Help me tune my timing

    Ok raising initial to 18 only affected off idle manners. It didn't affect the issue at hard acceleration at all.

    Can you explain what the concept behind changing the cam setting to street/stock will do for the engine so I'll have an understanding? Thanks for the help as always Gerry.

  3. #23

    Default Help me tune my timing

    JWZ28 wrote:

    Ok raising initial to 18 only affected off idle manners. It didn't affect the issue at hard acceleration at all.



    Can you explain what the concept behind changing the cam setting to street/stock will do for the engine so I'll have an understanding? Thanks for the help as always Gerry.

    Actually, I can't. All I know is that mine ran like crap on the performance setting, so I was on the mild setting for a long time. My cam specs put me in the mild setting. I have a 489 ci engine and I know that bigger engines tame down a cam a bit, so I tried the street stock setting just to try it. It seems to work for me. Another thing is that in the instructions I believe it says to open the throttle plates a half turn for a stock, one turn for mild, and one and a half turns for a race cam. My throttle plates are open less than a half turn to get my IAC below 10.

    My cam also idles with 13" of vacuum, like yours, except my idle speed is set for 825.

    I have no idea what the different cam selection actually changes, but I would like to find out. I've read that it adds fuel, but that makes no sense to me because I think the atomic would learn and change it back.

    Gerry

  4. #24

    Default Help me tune my timing

    Each of the "cam profiles" define the fuel / air map across the band. Street/Stock is close to a stock engine, Mild is a bit more aggressive and strip, well it is much more.

    You offset the pre-defined settings in the profile by adding or removing the PV percentage which will add fuel throughout the band to move you closer or further from the next profile.

    Fuel maps are a fluid thing with the learning feature on the Atomic. You tell it what you want and give it a baseline, Profile, and then you tweak it with the PS and PV and timing etc to make the engine happy.

    Does this help?

  5. #25

    Default Help me tune my timing

    Thanks a ton fcsallan. That's exactly what I needed.





    So hypothetically if I were lowering the pv and raising the ps, I'd be richening up my profile closer to the street stock setting. Likewise, needing a leaner condition would call for performance profile for a more efficient engine? (I was told that street/stock was the richest setting, performance the leanest).

  6. #26

    Default Help me tune my timing

    No, actually the performance is the highest concentration of fuel to satisfy hungry engines so it would be the richest. Street/ Stock is the sipper.

    I also think the PV setting is opposite what it appears, the higher the number the more vacuum it would need to provide additional fuel, just like a power valve in a carb. I could be wrong on this part though, I'm really just relating to the function of the PV in a carb and assuming.

  7. #27

    Default Help me tune my timing

    Well fellas, we've figured it out. Based on the explanation about the fuel maps and the pv/ps relation to the fuel maps you gave me fcsallan, I was able to make some educated guesses and adjust accordingly.



    Gerry, you gave me a theory on another thread of mine about the power valve feature, and with it I determined based on that theory that I had the PV adjusted too low. At key on engine off my MAP is 29.4. Engine running its between 15-15.5. 29.4 minus 15.5 is 13.9, and half of that vacuum reading would call for a power valve in a carb of around 6.95. 6.95 is about 23% of 29.4. SO, I adjusted my PV to 23% for starters.



    I also noticed last night how rich the exhaust smelled after blipping the throttle. So I backed the PS down to 30 as a starting point.



    I warmed the car up with the new adjustments, took it for a spin, and WOW! No more stutters or surging and the decel popping is nearly gone as well. This thing runs GREAT!! Not to mention the timing control cured the stalling issue I had when coming to a stop.



    Thanks for all the help once again, fellas. I'd send you both a 6 pack if it would stay cold. Hopefully this thread will serve to cure some issues for others in the future.




  8. #28

    Default Help me tune my timing

    JWZ28 wrote:

    Well fellas, we've figured it out. I'd send you both a 6 pack if it would stay cold. Hopefully this thread will serve to cure some issues for others in the future.





    Excuses, excuses... We both own refrigerators!





    Glad it's running good! Do us all a favor and post up all the settings that you ended up with. That would be the best help to anyone finding this thread in the future.




    Gerry

  9. #29

    Default Help me tune my timing

    GSchafer wrote:

    JWZ28 wrote:

    Well fellas, we've figured it out. I'd send you both a 6 pack if it would stay cold. Hopefully this thread will serve to cure some issues for others in the future.





    Excuses, excuses... We both own refrigerators!





    Glad it's running good! Do us all a favor and post up all the settings that you ended up with. That would be the best help to anyone finding this thread in the future.




    Gerry

    HAHA I'll gladly buy you a beer anytime!



    1978 Camaro Z28 (3500 lbs)



    Engine: Chevy 355 (350 .30 over)

    10:1 compression

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

    3.73 posi rear

    4 speed manual

    Atomic is controlling timing



    Here are my final settings:

    Cam setting: Mild

    Idle Target: 900

    AFR: 14 idle, 14 cruise, 12.8 WOT

    Pump Squirt: 30 (this may change a bit)

    Power Valve: 23



    Timing:

    Idle RPM: 1000

    Total RPM: 2500

    Idle Advance: 18 degrees

    Total Advance: 34 degrees (I may try 36 just for laughs)

    Vacuum Advance: 10 degrees unported





  10. #30

    Default Help me tune my timing

    Thanks for the assist guys.

    Thank you JW for the feedback.

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