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Thread: Help me tune my timing

  1. #11

    Default Help me tune my timing

    Things are completely different with the FI and the HEI. The characteristics of a carb vs FI is night and day. They each have their place, but in the end FI will win for drivability.

    An off idle stumble is more likely a need of a little more fuel at tip in. I would add a couple of clicks on the PS and see if it gets better. Fuel injection also likes a fast timing ramp. You might try lighter springs on the dizzy to get all in closer to 27 or 2800.

  2. #12

    Default Help me tune my timing

    fcsallan wrote:
    Things are completely different with the FI and the HEI. The characteristics of a carb vs FI is night and day. They each have their place, but in the end FI will win for drivability.

    An off idle stumble is more likely a need of a little more fuel at tip in. I would add a couple of clicks on the PS and see if it gets better. Fuel injection also likes a fast timing ramp. You might try lighter springs on the dizzy to get all in closer to 27 or 2800.

    What I meant is that when I was running the fuel injection with my HEI distributor (no timing control) there was no stumble or surging, so I'm sure it can be tuned out of the the system with controlled timing. There are no more springs or weights with my setup because now I AM running controlled timing with a pro billet distributor and phasable rotor. My curve right now is 12* initial, 32* total, 10* vac advance, and all in at 2500 rpm.

  3. #13

    Default Help me tune my timing

    Ok here are my latest adjustments and observations



    I fixed the connection that seemed loose



    Lowered the PV to 11



    Raised PS to 42



    Increased total advance to 34 at 2500



    IAC warm is around 10ish



    Observations:



    Tip in seemed greatly improved. It still surges and pops when I lay into it but didn't seem quite as bad (may just be a fluke but it seemed consistently better).



    I made sure to observe my A/F, fuel pressure, and timing on hard acceleration. A/F drops from 14 to down around 11/12ish just as it should. Fuel pressure stays consistently up between 50-60, no odd dropping out or cavitation. Vac advance drops out just as it should and timing reads 34 deg just as it should. It's almost not much of a surge right now, it's more like it pops and stutters.



    Could my timing curve be too quick? I'm wondering if what I'm experiencing is engine ping?



    When I pulled back into the garage I tried to give it a couple free revs and it wasn't smooth at all. It just pops and stutters and generally sounds awful, the same as my higher rpm runs.






  4. #14

    Default Help me tune my timing

    Which cam setting are you using? PV of 11 would suggest a low vacuum engine and would add a lot of fuel to the curve. The PS of 42 is real high. That dumps a lot of fuel in at tip in.

    These settings, if they perform fairly well, would suggest that you need a higher cam profile. If Street/Stock, then mild might work better. Just note, you have to reset and tweak the settings again if you make that move. All of the timing and fuel settings will be effected by this change.

  5. #15

    Default Help me tune my timing

    I'm using the mild cam setting. I tried performance a while back but it would barely even stay running on that setting. It has always run best on mild.



    My cam is a Lunati Voodoo 489/504 lift, 227/233 duration @50. I understand I'm on the edge between mild and performance setting, but it just doesn't run well on performance.



    You had mentioned increasing the pump squirt up around 35-40. 40-42 seemed to really help the tip in, so maybe it does need a lot of fuel. But then again, when I tried to free rev the engine, it popped and stuttered. I can't decipher whether this is a fuel issue or a timing issue.



    The MAP reads 15-15.5 at idle (29.5 engine off key on). If I'm reading that right, that means I have about 13" vacuum at idle, not low at all.



    The car does pull hard under heavy acceleration now, but I'm still getting the popping, stuttering.



    You had mentioned dropping the PV down around 12. Should I add some pv back in? If so, how much?



    Is my timing curve too quick? 12 initial, 34 total, all in by 2500? Maybe drop the total to 30 to see if I am experiencing ping?



    Any other suggestions?








  6. #16

    Default Help me tune my timing

    I still have the issue. Anything else I should try?



    Just to cut confusion, here are my current settings



    Cam: mild (I've tried performance but it ran so poorly it was dangerous)

    Idle Target: 900

    AFR: 14 idle, 14 cruise, 12.8 WOT

    Power Valve: 11

    Pump Squirt: 40

    IAC: 10 warm

    MAP: 29.3 key on engine off, 15-15.5 warm/running



    Timing

    Idle RPM: 1000

    Total RPM: 3000

    Idle Advance: 12 deg

    Target Advance: 34 deg

    Vac Advance: 10 deg unported



    I'm still getting a pop/stutter under heavy acceleration. I also get popping and stuttering when I'm sitting still and try to free rev the engine. Fuel pressure is nice and steady, no pump cavitation. Timing reads correct on handheld. AFR's read correct whether idling, cruising, or WOT.

  7. #17

    Default Help me tune my timing

    Try bringing your idle timing up from 12 to 18. Also, with the vacuum you are running with, you might want to try the street stock cam setting.

    Gerry

  8. #18

    Default Help me tune my timing

    Ok should I try 18 initial even with the 10* vac advance?



    I understand the street/stock setting will throw more fuel at it so that makes sense I guess. I'll do comprehensive reset and give it a shot. Thanks



    Any other pointers would be much appreciated. I'm not quite the guru some of you are yet.


  9. #19

    Default Help me tune my timing

    JWZ28 wrote:

    Ok should I try 18 initial even with the 10* vac advance?



    I understand the street/stock setting will throw more fuel at it so that makes sense I guess. I'll do comprehensive reset and give it a shot. Thanks



    Any other pointers would be much appreciated. I'm not quite the guru some of you are yet.





    Yes, try 18 initial with the 10* vac advance and your current cam setting. Let's see if it likes it. Then maybe try the street stock cam setting. Remember, one thing at a time!





    Gerry

  10. #20

    Default Help me tune my timing

    UPDATE: I increased the initial timing to 18*. The car really seemed to like it. The popping and stuttering while free revving is gone. Nice clean revs.



    Everything else stayed the same. It still surges and pops on hard acceleration, though it pulls really hard. Not sure if it makes a difference with hard accel, but my IAC was down at 0 after the timing change. I adjusted it back into the recommended range after the drive.



    What else can I try? It seems to run great on this cam setting besides the surging/stuttering. Should I go ahead and try street/stock?



    I did notice lots of popping in the exhaust when it surges and on decel. If I'm not mistaken, the popping is a symptom of unburned fuel igniting in the exhaust (at least on decel). Could it be that I need to go higher with my power valve enrichment to back some fuel out of the curve?



    Is it possible that it needs a little more timing up top, say 36*, seeing as how some extra timing at the bottom cured the issue while revving at idle? Or do my symptoms seem like pre-detonation and need a broader advance curve?




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