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Thread: Need help figuring out why it's pulling timing.

  1. #1
    Advanced Tuner abc's Avatar
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    Need help figuring out why it's pulling timing.

    Went to the dyno today to test ignition advance settings with E85.
    I noticed it was pulling 2.5 to 4 degrees above 6300 rpm. Don't pay too much attention to the timing map as I was adding to it just as a test. I looked at all the modifiers and I haven't found the reason why it would be pulling timing. On the attached log and .hpt file I removed the the torque management for the 3-4 shift and added to the 1.2g row, copied the low table to the high table as my last test. This was the the least timing it pulled out of the 4 test hits we made. Is there something in the Gen 3 PO1 PCM working in the back round that HPT doesn't give us access to that may be causing this or did I just over look a modifier somewhere?
    Is there a torque management issue that may be causing it?

    I gave up for the day when the blower belt started slipping in excess and realized I couldn't find the answer to why it was pulling timing. Any and all help is appreciated.

    dyno pull 3.hpl
    red rocket 66 added VE for corn.hpt

  2. #2
    Advanced Tuner abc's Avatar
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    We did a pull in 2nd gear to run a different test early on and I just noticed the timing appears to be locked in on the High Octane table. Are we sure when in SD the PCM only uses the low Octane spark table? I attached that log and .hpt file used for the second gear pull.
    2nd dyno pull.hpl
    red rocket 64 added VE for corn.hpt

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    Quote Originally Posted by abc View Post
    We did a pull in 2nd gear to run a different test early on and I just noticed the timing appears to be locked in on the High Octane table. Are we sure when in SD the PCM only uses the low Octane spark table? I attached that log and .hpt file used for the second gear pull.
    2nd dyno pull.hpl
    red rocket 64 added VE for corn.hpt
    Are you playing a joke? It has the 2bar SDOS applied. Both tables are used. Spark in the log matches the High Octane table...

  4. #4
    I assume there isn't a work around for the 1.2? The boost PE makes up for it? I assume you go pass it with boost.
    Quote Originally Posted by blindsquirrel
    Hey bud, click this link, it will not make me even a little upset: https://forum.hptuners.com/profile.p...ignore&u=44277

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    Senior Tuner edcmat-l1's Avatar
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    Quote Originally Posted by DodgeZ View Post
    I assume there isn't a work around for the 1.2? The boost PE makes up for it? I assume you go pass it with boost.
    165f57fe0caa48c8b9ca91771927a55b.jpg

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  6. #6
    Quote Originally Posted by edcmat-l1 View Post
    " added to the 1.2g row" airmass
    Quote Originally Posted by blindsquirrel
    Hey bud, click this link, it will not make me even a little upset: https://forum.hptuners.com/profile.p...ignore&u=44277

  7. #7
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    For modifying past the 1.2g max on the spark axis, use the Fuel spark table. As PE increases do something with spark. Think about what's going on and adjust accordingly.

    For big boost and big injectors scale the injector data. This'll trick reported airmass.
    Last edited by SiriusC1024; 10-05-2024 at 10:25 PM.

  8. #8
    Advanced Tuner abc's Avatar
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    Quote Originally Posted by SiriusC1024 View Post
    Are you playing a joke? It has the 2bar SDOS applied. Both tables are used. Spark in the log matches the High Octane table...
    I have been working with the understanding when switching to a SDOS only the low octane table was active. With your statement I assume you are telling me I am wrong? At some point the two tables were not a copy of each other. The point of mentioning the pull in 2nd gear was to make note that the timing was proper and in 3rd gear it is not proper and does not reflect the high or low octane table. If you look at the 6400 rpm point in the 3rd gear pull, the spark tables are commanding 19.01 advance and the log is reporting 17.5.

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    For the 6400 part look what the IAT modifiers are doing.

    High and Low are used in SD with the custom OS's.
    https://www.hptuners.com/help/VCM-Sc...tt_os_mods.htm

  10. #10
    Advanced Tuner abc's Avatar
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    Quote Originally Posted by SiriusC1024 View Post
    For modifying past the 1.2g max on the spark axis, use the Fuel spark table. As PE increases do something with spark. Think about what's going on and adjust accordingly.

    For big boost and big injectors scale the injector data. This'll trick reported airmass.
    Are you talking about the ECM 12626 table?

    I also have been operating with the understanding that as the cyl. air mass surpasses the 1.2g row it continues to use the last commanded value of the 1.2g row, is this understanding also wrong?

    I haven't studied much about scaling the injector data as I didn't think we were in the neighborhood of needing to trick the reported air mass at this point. When do you know you need to scale the injector data to trick the reported consumed cyl. air mass?

  11. #11
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    That and the two multipliers. IAT is subtracting 1-2 degrees.

    It's on the 1.2 row. Reported cylair got to 1.45. Since there's not going to be much in-between (part throttle WOT?) you can put the timing you want for 1.45 into the 1.2 row. If you'd like to control it then use the Fuel Base table to command spark modification based on PE and RPM. PE is based on MAP for boost enrichment. So think of it as modifying cylinder airmass spark in a roundabout way.
    Last edited by SiriusC1024; 10-06-2024 at 12:55 AM.

  12. #12
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    Quote Originally Posted by SiriusC1024 View Post
    For the 6400 part look what the IAT modifiers are doing.

    High and Low are used in SD with the custom OS's.
    https://www.hptuners.com/help/VCM-Sc...tt_os_mods.htm
    Thank you for the link, that clears it up for me.

    I was looking at the IAT mod. table and suspected maybe the the log is just not updating as fast as the IAT is rising and this is the table that is actually pulling the timing. I wanted to remove the -1 degree at the 113 degree point for a test but stopped short due to the belt slippage. Is this where you are trying to lead me?

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    No. Where I'm trying to lead you is that logged spark is following what's commanded, and nothing is wrong. At 6400rpm, 1.20g cylair the High Octane base spark table is 19.01. IAT modifer for 117F is about -1.5. IAT multi is 1. IAT Mult2 is 1. IAT*Mult*Mult2. ECT modifier is 0 degrees at 184F, so no effect. The other modifiers have been zeroed - no effect.

    19.01 - 1.5 = 17.51.

    Log shows 17.5 degrees at 6400rpm.

  14. #14
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    Quote Originally Posted by SiriusC1024 View Post
    Since there's not going to be much in-between (part throttle WOT?)
    I'm not following you on this statement, can you elaborate?

    As far as the rest of that post, I believe I understand now, thank you.

    Assuming that the IAT table was the table that was pulling the timing, I would like to verify it but, I will certainly leave it active in real world daily driving.

    In your guys experience, what does your IAT base correction timing table look like? Do you have a rule of thumb for when you start pulling timing?

  15. #15
    Advanced Tuner abc's Avatar
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    Quote Originally Posted by SiriusC1024 View Post
    IAT modifer for 117F is about -1.5.
    I guess this is where my confusion is coming in and why you thought I was joking with you. When I scroll through the log on my end the reported IAT does not go above 93 degrees until after the pull is aborted. How are you seeing 117F and what should I do on my end to see it the way you are seeing it?

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    I thought you were joking about the High Octane table. Most people know that the custom OS allows for it.

    Here's your log. WOT pull. 6400rpm and climbing, 117F IAT, 1.20g cylair row.
    log iat.png

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    Quote Originally Posted by abc View Post
    I'm not following you on this statement, can you elaborate?

    As far as the rest of that post, I believe I understand now, thank you.

    Assuming that the IAT table was the table that was pulling the timing, I would like to verify it but, I will certainly leave it active in real world daily driving.

    In your guys experience, what does your IAT base correction timing table look like? Do you have a rule of thumb for when you start pulling timing?
    Try making it report 1.20g cylair with the pedal. You'll spend a lot of time. When driving it's idle, cruising, or WOT, so it doesn't really matter if you use 1.45 timing for the 1.2 row. 1.2 row is WOT.

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    Couple more tips.

    That dip in the VE, specifically that VE is decreasing with boost, tells me that IAT isn't reporting accurately.
    iat sensor location bias.png

    If the IAT has been relocated to the manifold, as it should be with boost and SD, then start by zeroing out Airflow>Complex Charge Temperature>Bias. Wideband is showing PE is way leaner than commanded. Make the hardware adjustments then the software adjustments then VE should come in a lot more accurately.

    E85 likes to run fat. Try adding 0.05-0.1 to your PE tables to richen up commanded even more.
    Last edited by SiriusC1024; 10-06-2024 at 01:54 AM.

  19. #19
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    Quote Originally Posted by SiriusC1024 View Post
    Try making it report 1.20g cylair with the pedal. You'll spend a lot of time. When driving it's idle, cruising, or WOT, so it doesn't really matter if you use 1.45 timing for the 1.2 row. 1.2 row is WOT.
    Understood, thank you.

  20. #20
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    Quote Originally Posted by SiriusC1024 View Post
    Here's your log. WOT pull. 6400rpm and climbing, 117F IAT, 1.20g cylair row.log iat.png
    I don't view the gage chart for the IAT. I only use the data reported in the PID list for something like this. Why do the two not match? Now that I know they do not match, I assume I should add it to the chart vs time?
    Do they not match because I logging too many PID's?