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Thread: Why is idle timing so much lower than 4 tables?

  1. #1
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    Why is idle timing so much lower than 4 tables?

    2024_0524_SD Test 17_LQ9timing curve.hpt2022_0527_SD with tune17.hpl

    Trying to get my idle better. I noticed the timing is much lower than commanded in any of my 4 spark tables, and any corrections are either zero'd out or add to the spark, other than overspeed.
    I know the VE needs a little update based on the data, but i really want to get the idle lined up... it's the only thing scaring me from going for a longer ride

    Any help would be greatly appreciated

  2. #2
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    Your VE table is spikey, id highlight the area and click the smooth selection 2 times.
    idle is something you focus more on the end of VE/timeing/MAF tuning
    once warmed up to op tempt everything looks like its working, go for a drive, get that VE dailed in

  3. #3
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    Thanks BK. I'll smooth out the VE, but what in the tune is even causing the pulling of 6-10 degrees? I cannot find it

  4. #4
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    Idle timing is lower than commanded because the Overspeed spark adaptive is removing spark to maintain idle.

    Why are you trying for 26*? Should be 18*.

  5. #5
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    Why 18?2024_0526_SD Test 20.hpt2022_0527_SD with tune20.hpl

    I have an LS1 base tune (my car is an 02 trans am) and a stock LQ9 tune. Both have idle spark >20 (LQ9 is 20, LS1 is 24-ish).
    Everything I read said to bring it up a couple degrees to get it to fire.

    Here's my last run at 24 degrees.

  6. #6
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    So it is the overspeed that's taking out the timing?

    I feel like it's getting a ton closer but I have 2 issues.
    1 is that when i left off the clutch in 1st, it bucks pretty good.. i have to ride the clutch to keep it moving.
    The other is driving between 1000 and 1400rpm.... I know the Idle cracker and follower are killing me here but don't know how to fix.
    Any help would be greatly appreciated.

  7. #7
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    Don't even waste your time with idle stuff until VE is correct.

  8. #8
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    VE is getting close, outside of the 2800-4000 range which requires a little more spirited longer driving.

    And I'm trying to make sure the idle at least stabilizes a bit; when it drops to 400rpm i get pretty worried about stalling. That's part of the reason I'm not taking a longer drive.

    Sirius, why do you say Idle needs to be at 18 degrees?
    I can't find any ground truth on idle spark values, so would love to hear the explanation. I'm happy to change to that if I need to

  9. #9
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    Can someone check if my cracker and follower are fighting with each other?

    The 1000-1500 stumble seems like the cracker and follower are both active, which makes zero sense to me

    The 1:30-2:00 min range and the 8:00 range.
    I've done my best not to mess with this, but I feel like it's something that I need to learn more about


    Also, at the very end of the log, i backed out of my driveway, and pulled back in... in both cases, RPMs dropped down in the 400 range, which I cannot understand..... would REALLY like some help in this area




    2024_0526_SD Test 22_post RAF setting.hpt2022_0527_SD with tune22.hpl

  10. #10
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    Lower your idle spark. When RPM dips and your underspeed becomes active it is clamped at 24 degrees from your HO table. In other words you have pretty much 0 torque reserve lol. What was done to the engine?

    Your VE is rich on coast down which isnt helping anything either.

  11. #11
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    LQ9, elgin SS2 cam, 243 heads.

    Lower to what?
    And I thought in SD mode, the Low octane table is used?

  12. #12
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    Yeah it is used, Your timing is copied over to the LO so it is still 24 degrees. Try between 15 and 19 degrees. Id also raise your HO, in this case LO, a little more, maybe high 20's in the idle regions. You are going to need to adjust Throttle Cracker/Follower for that cam. Main thing is get your fueling tighter for now. Log TPS too not just voltage.

  13. #13
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    So are you saying to lower the LO table to 18, and up the HO table above 24? I have 93 in the tank but know in SD it's using the LO table. I'm kinda confused.

    Also, how do i adjust the cracker/follower?

  14. #14
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    No. Lower the idle regions of the Idle Spark tables. Raise a few degrees in the idle regions of the HO/LO spark tables. I wouldnt adjust the throttle cracker/follower tables until your fueling is dialed in and it is pretty far off yet especially the coastdown/idle areas which is important for return to idle situations. One thing at a time.

  15. #15
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    Alright so i took down the idle tables to 18 and upped the low and high octane a little.
    Overall feels similar to prior, but a couple times the rpm dropped in the 400 range and i got pretty worried it'd stumble out (power steering also got pretty difficult).

    How do I keep the idle when the clutch gets depressed to stay?

    (I updated the VE table based on those errors, but didn't get a chance to re-log yet.)




    2024_0526_SD Test 23.hpt2022_0527_SD with tune23.hpl

  16. #16
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    You don't have STIT logging. Maybe I missed it.

    This your fast idle airflow trim. Work on getting it to zero or slightly negative. like -0.5g.

    I'll bet it is very negative right now and the adaptive over/under tables are putting the idle timing where you wouldn't expect it.

    Also looks like your follower and cracker are more active than they would be stock. I'm not a fan of using these too much because adaptive airflow is disabled while either is active or still decaying to zero.

    BTW. Your IAC counts are fairly high and the throttle body could use an adjustment. I have a how to on my website. If you'd like me to find it for you I will.
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  17. #17
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    It's under Idle Adapt, but always zero in this run.
    My Run 22 has it at -0.33 at times but it rarely registers any value.

    My follower and cracker values are from a stock LS1. Should I change it to the stock LQ9?
    I agree that they seem to be playing with my idle and I have NO idea why they're getting involved when i'm driving at lower RPM, but have no clue what to change to

    I've read that IAC counts should be 30-50 or 40-60 then others who say it doesn't matter as long as it's not zero or pegged >200. Seems to change with spark; 30 deg produced different values from 24 from 18.
    Is there any real reason to be in the 50 range and not 100?

  18. #18
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    Somewhere between 30-50 fully warmed up is pretty good. I don't like them to be 100's fully warmed up. You need reserve for when it is cold.

    I would put all the follow and cracker stuff back to YOUR stock tune. There are modifiers and multipliers that we can't see. So if one has a follower of 1, doesn't mean the next car with 1 will have the same result...

    But anyway.. as long as either of those are active STIT is not and the idle is basically not being controlled at all by the IAC
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  19. #19
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    I don't plan on every driving this car below 50 degrees outside... this is gonna be my toy car and only driven when the top is down.

    So back to my "stock tune." What does that mean? My stock tune is an LS1 for the Firebird that the engine is in... But the engine is a modified LQ9. I don't enough about the cracker/follower to know which to use. That's good to hear that while those are working, the STIT won't... explains the situation, but i'm not sure how to get the cracker/follower to be inactive.
    I clearly am not smart enough on this yet.

  20. #20
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    Here man. Play around with this. You know to use VCM Scanner to clear LTFT's after each tune update?
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