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Thread: 7730 tuning help with A1 file

  1. #1
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    7730 tuning help with A1 file

    Hello, needing help on tuning. I have an 88 Fiero GT. 3.4 swap, truleo intake, Sprint headers 17# injectors, mild cam,1.6 roller rockers, fidanza aluminum flywheel, 7730 with DIS. EGR delete,underdrive pulley, heads were ported. It starts and runs. Lots of power. It idles fine when warming up but once it's warm and idle drops the idle surges. Give some throttle and it will die under deceleration. I talked to someone from a local tuning shop and one of the things he said was my light flywheel is probably causing the surging due to the lack of inertia. He suggested turning up the idle. Wandering what you all think about that and if so how do I do that in tuner pro using A1 mask? The guy at the shop said turn the adjustment screw on throttle body, but I was hoping to tell IAC to allow more air if that's possible. Thanks in advance for any and all input.

  2. #2
    Fuel Injected! steveo's Avatar
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    yes you need a bit more idle speed with a light flywheel, what you really want to do is set the target idle speed in the bin a bit higher, but you might find it still surges.

    a datalog will show you if IAC feedback is contributing to it (you'd see the iac counts up and down quite a bit) in which case altering some iac parameters might be necessary, to bring it back to its rpm target more slowly.

    the timing advance at idle is also critical with a light flywheel, you could play with that a bit.

    another trick for engines that persistently stall when you get off the throttle really quickly is to add quite a bit of timing and a bit more fuel in 'stall' range (say under 400 rpm and under 40 map). that way when it's falling off that cliff, the extra fuel and spark will act like a trampoline. it should fall back more gently after that initial boost, by which time the IAC might be able to keep it going. i've used this on engines with static idle (no IAC valve at all)

  3. #3
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    That's good info thank you. I'm really ignorant when it comes to tuning though. The way things are labeled in the program I cant seem to figure what to change . They say something vs something. Do you know what scaler to make these adjustments under the A1 mask. For example if my IAC is up and down a lot do I decrease the step size to slow it down? Not in front of a computer right now but I will look at it later and try to figure it out.

  4. #4
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    Looking at the data log I do see that the IAC is trying to keep up with idle. down as idle increases and up as idle goes down. Im not seeing any parameter option to slow it down. most options have to do with A/C, TPS and start up temps.

    as for adding timing and fuel, is that going to be done in the idle VE table. also what would be a bit? I wouldn't want to change to much and mess up something.

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  6. #6
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    A1_tpv5.xdf

    that should be it. Hope that works

  7. #7
    Fuel Injected! steveo's Avatar
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    start by increasing your idle speed:

    Commanded Idle Speed in Drive (F17)
    Commanded Idle Speed in Park/Neutral (F19)


    this is per temperature, so you can actually datalog what the temperature is when it starts running like crap and only change those cells. i would increase your idle RPM by 200 and see how that goes.

    your ecm mask actually has the timing advance trick built in, it's in these tables.

    Idle Spark Retard vs Idle Error (F1SPRTD)
    Idle Spark Advance vs Idle Error (F1SPADV)


    the way it works is, for example, if your idle speed is 50rpm low, it will add spark advance from the advance table's 50rpm column, trying to make up for that error. if it's high, it will reduce spark advance using the retard table.

    one thing to understand when trying to stabilize a modulation (a surge) is trying to tune out the modulation completely often results in the control system itself creating a new modulation instead.

    in my experience with an aluminum flywheel, increasing the values in the advance table and reducing the values in the retard table will help (it'll allow it to surge 'high' but fight harder to prevent it from surging 'low'). i would keep the values under 50rpm very low, though.

    try that stuff first.

    you have an IAC throttle follower going on too. if the stuff above doesn't quite do it, playing with this table should allow you to affect how quickly your IAC falls.

    Throttle Follower Decay Rate vs MPH (F129)

  8. #8
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    Thank you for all the help. I really appreciate it. It will work on this this weekend. One question though, does it matter that I have a 5 speed? It's worded like it for automatics(drive,park,neutral). I forgot to mention before it's a manual, not sure if it matters.

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    There should be a Flag for Manual Transmission. Often when this flag is set tables for park are used at all times.

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    Fuel Injected! woody80z28's Avatar
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    I run a 3400 in Beretta on $A1 7730. The surging idle is hard to fix. The biggest improvement I found was actually replacing my Bosch o2 sensor with a Denso. Had a few friends that had the same problem and they all improved with a Denso o2.

    Once I cammed it, I cut both the idle spark vs idle error tables in half and it helped.
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

  11. #11
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    Not sure what O2 I have and don't remember when or if I replaced it. I was thinking that I replaced it at some point but not sure. My engine is the 3.4 pushrod, since you said 3400 I'm assuming its the roller cam with aluminum heads. not sure if that makes much of a difference.

  12. #12
    Fuel Injected! woody80z28's Avatar
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    Mine is the pushrod gen3, but that shouldn't really matter to the o2 sensor.
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

  13. #13
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    Sorry it took a bit to get back on here, it started raining last week and trying to finish up too many projects before winter. I increased idle in the F17 and F19 tables to 1100 so at no temp it goes below that. It idles smoother for sure but still dies after the tiniest bit of throttle. I gave it gas enough to increase the rpms a few hundred but as soon as I let off the gas it dies every time. So I'm thinking its something other than low rpm and the surge causing it to die. Any idea? One thing I noticed is it is running rich at start up. doesn't hit target AFR till closer to 100deg.

  14. #14
    Fuel Injected! woody80z28's Avatar
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    Hmmm. That's something I've never heard of. What does the injector pulse width go to when it dies? Watch the log history and see if it falls off a cliff.
    80 Camaro Z28 - 550hp AFR 383 / T56 6spd (Holley HP EFI)
    91 Beretta "SS" - 260hp 3400 MPFI / HM282 5spd (7730/$A1)
    94 Silverado Z71 - 300hp Vortec 357 TBI / NV4500 5spd (7427/$0D)

  15. #15
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    I see Injector duration in my logs, assuming that's the same. This drops way down right before it dies. Curious about tps too, it's way up, down, up than dies.

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