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Thread: Weird minimum spark issue

  1. #1
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    Weird minimum spark issue

    Twin turbo / cammed LS2 - I can't seem to figure out a weird minimum spark issue at WOT. Seems to occur at the same point during each run. I've looked everywhere I know to look, and can't figure out why it's doing it. Scan and tune attached.scan-7-5-1.hpltune-7-5.hpt

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    I had this issue a few years ago on an E67. It ended up being something that user defined parameters was able to solve. HPT doesn't have everything defined, so you won't be able to totally shut down torque management. You'll notice the torque management min spark is the table the spark is riding on during those events. If you have user defined parameters you can flush out those unseen calibrations.

  3. #3
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    What do you mean user defined parameters?

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    Yeah, I am also curious about this. I did another pull and there is no Fuel/Spark/ETC TM occurring according to the scanner, but that timing is still dropping down to 5 degrees. And its not even max boost or RPM, fueling looks good, no knock, etc. No reason for it...?

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    My thoughts are that you have traction control on.... I see that the Minimum "base" torque management timing chart is being applied right when your about get into boost.... I found it spark -> advance -> bottom right(scroll down)

    My suggestion turn off traction control, or maybe Match the (base)chart to your timing map for those cells

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    You need to record spark torque management type and/or spark control source. Spark arbitration will always choose the lowest commanded spark request unless that value is below any of the defined minimums. Your nominal spark request doesn't ever go as low as 5 degrees, so I wouldn't be looking at that table. But your torque management min spark table is also set to 5 degrees and you have an event at 57.3 seconds in where a mild tip-in is driving spark down to 5 degrees at 0.26g and 700rpm. Trans, traction control, even ABS spark reduction requests will abide by that torque management min spark value. Gotta record which type it is.

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    Lakegoat: Looking at Spark / Advance / Fuel / Gas, I see the values there, but they look to be adding spark, not taking it away. Unless I'm misunderstanding something. FYI this is E85 only.

    smokeshow: I've included a scan where I log the TM type (all 3) and none of them show as active during the event. Is there another type I should be logging? You also mentioned ABS...the ABS and traction fuses are pulled so that shouldn't be active.

    scan-7-6-1.hpl

    Also of note, this scan also has a pull in it where this event doesn't occur until the shift (look at the end of the scan).
    Last edited by eclipse5302; 1 Week Ago at 11:52 AM.

  8. #8
    Advanced Tuner jsllc's Avatar
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    The tune says this is an E67. I do not remember any 6L engines using this so it must be from another? If so what was it. There a few things wrong. If it is not an E67 then what is it?
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm

  9. #9
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    Need more information. I had to look at another thread to see what model and year this is. Log desired torque, everything torque management related. Don't care about response rate, just looking for something to jump out. Also, is your AC on?

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    Yes, it's a 2007 TBSS 6.0, twin turbo/E85 with a 4L80E. A/C is never on during these events, and transmission is usually in 3rd (D).

    I added any and all torque / TCS / TM scanner PIDs I could find and went for a drive. Resulting scan is attached.

    scan-7-6-2.hpl

    First event is 3:07, light throttle take off from stop, and I see "Spark Torque Management type: Trans". No shift occurring. I don't recall seeing that before.

    Second event is 3:52, tip-in from coasting. No TM "type" being displayed, although "Torque Mgt Advance" is showing as 16.8 degrees. This occurs a number of times throughout the scan, sometimes pulling as much timing to hit the minimum 5 degrees. Now, considering I have all of the master enable/disable settings for any tip-in limiting, TCS, etc disabled, where is this coming from? Is this a matter of these settings needing to remain "enabled", but reduced with the numbers instead?

    There is another event at 4:54 (WOT) where it goes to 5 degrees timing right as it's getting into boost, but Torque Mgt Advance is still 0.0.
    Last edited by eclipse5302; 1 Week Ago at 08:51 AM.

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    Actual TPS would be sweet lol. But I'm looking at it

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    Ok, I think I might know what is going on here. I think the stall torque mgt is what is causing this issue. I couldn't find much else as to why it would be doing any TM on a light throttle tip-in. I increased it to max, and the issue seems to be gone. Light throttle, WOT, etc...no weird dips now unless it's shifting. Which leads me to my next question regarding the minimum spark table.

    Consider a WOT 1-2 shift. At the shift point the torque is about 600 ft/lbs, and the trans torque reduction table is setup to remove 35%, which should reduce torque to about 414 ft/lbs. In my scan, it only drops to 520 ft/lbs, which is about 12%. If I'm at 17.5 degrees at the shift, and can only go down to 5 degrees, it'll never be able to hit the target reduction if the floor is set to 5. This is a built 4L80E, so maybe 35% is too much reduction during a shift...but I don't necessarily want to completely remove all TM. I do want it to shift nice at low load, and any attempts at reducing line pressure haven't reduced the harsh 1-2 at part throttle (probably due to valve body changes).

    Should I consider lowering the minimum spark table so the controller can actually do what I am asking it to do?
    Last edited by eclipse5302; 1 Week Ago at 11:02 AM.

  13. #13
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    I would disable what is still enabled and drive it around easy observing the effects. I was looking for proof of it being stall torque management or brake torque management or drag control, but don't have enough info.

  14. #14
    Advanced Tuner jsllc's Avatar
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    Quote Originally Posted by eclipse5302 View Post
    Yes, it's a 2007 TBSS 6.0, twin turbo/E85 with a 4L80E. A/C is never on during these events, and transmission is usually in 3rd (D).

    I added any and all torque / TCS / TM scanner PIDs I could find and went for a drive. Resulting scan is attached.

    scan-7-6-2.hpl

    I am attaching a video of the issue and the root cause. It is a large change in air over 20% without any known cause. ECM is just reacting.


    First event is 3:07, light throttle take off from stop, and I see "Spark Torque Management type: Trans". No shift occurring. I don't recall seeing that before.

    Second event is 3:52, tip-in from coasting. No TM "type" being displayed, although "Torque Mgt Advance" is showing as 16.8 degrees. This occurs a number of times throughout the scan, sometimes pulling as much timing to hit the minimum 5 degrees. Now, considering I have all of the master enable/disable settings for any tip-in limiting, TCS, etc disabled, where is this coming from? Is this a matter of these settings needing to remain "enabled", but reduced with the numbers instead?

    There is another event at 4:54 (WOT) where it goes to 5 degrees timing right as it's getting into boost, but Torque Mgt Advance is still 0.0.
    Issue is a large change in airflow (over 20%) for no good reason. ECM is just reacting to that. Easily seen before and after timing changes. This then changes cyl/airmass.

    Are you 100% certain the instructions for converting (patching) this OS to VE from VVE were followed to the letter?
    Last edited by jsllc; 1 Week Ago at 11:40 PM.
    2012 ZL1 - Maggie Heartbeat, Port & Polish Heads, Custom Cam, Custom rotating assembly, steel sleeved LS9, No NOS and No water meth. 16psi
    810rwhp and 820rwtq 91 Octane 6400 rpm
    948rwhp and 951rwtq 105 Octane 6400 rpm
    999rwhp and 997rwtq on 60% Ethanol 6400 rpm

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    I guess I'm not entirely certain they were followed exactly. The truck was tuned by a local tuner, but he left a lot to be desired. It went in with the VVE-based OS on it and came back with this, which I had to re-license. I spent a lot of time VE tuning the part throttle areas and just getting it running well for everyday driving. I'm just trying to get the bugs worked out.

    I've done a number of scans since raising only the stall torque mgmt, and I haven't seen that minimum spark issue return. I've also been working to understand the various TM settings and how they affect everything.

    I'm not sure if it matters or not, but this truck has low/remote mount twin turbos (in place of the existing muffler), with an A2W intercooler. They are BW S256SX turbos with AGP .63 turbine housings.
    2007 Trailblazer SS - LS2 | S256sx + S256sx | E85 | Built 4L80-E
    1991 Olds Cutlass Supreme International Sedan - L67 | GT35R | E85 | Built 4T65-E HD | NO2

  16. #16
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    The torque arbitration is pretty complex. There are about a dozen kinds of torque management that can come in and affect things which makes it critical to get as much scanner feedback as possible. I knew it was TM, but wasn't sure which.