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Thread: Reducing VT

  1. #1
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    Reducing VT

    Hi,

    2016 Chevy silverado with a L86 engine in it. Engine had a some head work and a cam installed. I don't know the specs unfortunately.

    I have the VVE tuned in closed loop to around 3-5%. Being on a chassis dyno, it helps to fill in the histogram with good data. I decided to tune the open loop region of it (zone 23 and 29) but I couldn't do anything good because the throttle was being pull back to around 50 %. I was kinda expecting it after all the posts in the gen V section. The maf curve isn't too far off so I decided to look into the issue more.

    With my virtual torque tables left stock and my DD tables stock, I decided to have a go at it. I bumped up the virtual torque tables by 10 % and it only made the throttle closure worse. I also bumped up the driver demand tables up by the same amount, same thing, throttle was being pull back worse than stock settings. I also tried a various combination of bumping those tables up to try and model the torque as best as I could, but anything else more than stock was just worse.

    Then, I went ahead and added 20% in the VVE table into zone 23 and 29. They way I understand it, is that the airflow model has to be as most precise as possible. Same thing, throttle was still being pulled back and even the fueling was not even changing. I bumped up the maf curve above 7350 Hz by the same 20% and same results. Engine goes lean above 5000rpm with the throttle at 50 %

    Then I did something, I decided to bring the virtual torque tables DOWN from the stock numbers by almost 35%. Same driver demand tables, same peak torque table, same VVE table that was calibrated with around 3-5% of error and the throttle does not close anymore. Strait at 90% the whole run. I understand I should have less torque at idle and cruise region but at WOT it should see more torque...I am sure I am not getting something because it doesn't make sense.

    Here are the logs and the tune files. The hpt tune "nomorethrottlepull" is the one with LESS virtual torque numbers.
    VVEtuningOK_MAFSCALING.hptpower_run3gear.hplnomorethrottlepull.hptno_throttle_pull.hpl
    Last edited by chuckk; 3 Weeks Ago at 03:40 PM. Reason: forgot to add logs

  2. #2
    Senior Tuner Higgs Boson's Avatar
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    I run completely stock DD and VT with 1000 rwhp on E85. You don't need to change them.

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    I appreciate your feedback Higgs, I know you're one of the experienced tuner with the gen v's. Would you have an idea why when I lower the VT the throttle doesn't close ?

    thanks again

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    how can you run stock VT tables on 1000whp? Your actual trq doesnt exceed max trq?

  5. #5
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by str8dum1 View Post
    how can you run stock VT tables on 1000whp? Your actual trq doesnt exceed max trq?
    So completely stock 100% row of DD, some of the part throttle section is lowered.

    I don't even measure the torque PIDs anymore because I don't think it matters.

    Honestly, my tune is MAF only with a stock VVE, VTT, DD (100 row), Peak Torque.

    Fueling is spot on at part throttle. Port injection handles fueling at WOT past what the DI can't handle (MAF curve is stock multiplied by 5%).

    Spark is commanded with no funny business. The only issue I have is what I thought was phantom knock retard above 4000 RPM but it's not there on E85 so the build just won't work on 93 octane.
    The next test is going back to full 93 to see just how much spark it will handle, probably 5-8 degrees, but it doesn't knock at all on E85 at 20, so I will just add it back in with the flex spark table.

    I have spent weeks upon weeks perfecting the VVE only to move it away from it's relationship with VTT. Sounds crazy but at this point I think they are too interrelated to change either of them until we fully understand how they work together with torque calculation, reporting, and control. The car is doing exactly what I want it to do with all of that stock. I suppose I am essentially letting the ECM think the car is still stock and letting the port injection pick up the difference.



    With that said, I am commanding stoich (EQ/Lambda 1.0) during PE fueling since I have port injection. The only other thing I haven't tried is changing the EQ Ratio Torque Model table to all 1.0 while commanding a richer PE, like 1.2 since that would correlate to the same thing I am doing commanding stoich for PE, the EQ Ratio Torque Model table never moves from the 1.0 column. Not sure there yet, a test for later to see what that will do.

  6. #6
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    Quote Originally Posted by Higgs Boson View Post
    So completely stock 100% row of DD, some of the part throttle section is lowered.

    I don't even measure the torque PIDs anymore because I don't think it matters.

    Honestly, my tune is MAF only with a stock VVE, VTT, DD (100 row), Peak Torque.

    Fueling is spot on at part throttle. Port injection handles fueling at WOT past what the DI can't handle (MAF curve is stock multiplied by 5%).

    Spark is commanded with no funny business. The only issue I have is what I thought was phantom knock retard above 4000 RPM but it's not there on E85 so the build just won't work on 93 octane.
    The next test is going back to full 93 to see just how much spark it will handle, probably 5-8 degrees, but it doesn't knock at all on E85 at 20, so I will just add it back in with the flex spark table.

    I have spent weeks upon weeks perfecting the VVE only to move it away from it's relationship with VTT. Sounds crazy but at this point I think they are too interrelated to change either of them until we fully understand how they work together with torque calculation, reporting, and control. The car is doing exactly what I want it to do with all of that stock. I suppose I am essentially letting the ECM think the car is still stock and letting the port injection pick up the difference.



    With that said, I am commanding stoich (EQ/Lambda 1.0) during PE fueling since I have port injection. The only other thing I haven't tried is changing the EQ Ratio Torque Model table to all 1.0 while commanding a richer PE, like 1.2 since that would correlate to the same thing I am doing commanding stoich for PE, the EQ Ratio Torque Model table never moves from the 1.0 column. Not sure there yet, a test for later to see what that will do.
    Have you tried maxing out your DI system so you don't flood your ports with fuel? Should make more power that way don't you think?
    How are the ZR1s blending it from the factory?
    2019 C7 ZO6 M7.

  7. #7
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by HeavyChevy305 View Post
    Have you tried maxing out your DI system so you don't flood your ports with fuel? Should make more power that way don't you think?
    How are the ZR1s blending it from the factory?
    Without playing with it on the dyno, I am not sure which would make more power. It makes more than it can put down at pretty much any speed as it is so I am not chasing any last 50 hp.

    I have maxed out the DI system, it basically maxes out on E85 as soon as I floor it, and tuning the MAF with a funky curve to try and balance it at the limit and feed in the port fuel just didn't work well. It works a lot better this way, like perfectly.

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    Quote Originally Posted by Higgs Boson View Post
    I run completely stock DD and VT with 1000 rwhp on E85. You don't need to change them.
    How could you then manage the idle timing with a cam?

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    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Eng.LSX View Post
    How could you then manage the idle timing with a cam?
    adjustments made in the Idle tabs

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    Quote Originally Posted by Higgs Boson View Post
    adjustments made in the Idle tabs
    What was the highest ignition timing you've reached at idle? I've only seen 2-4 degrees after adjusting the idle tables as the timing was in negative before that but could get more with VT.

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    Quote Originally Posted by Eng.LSX View Post
    What was the highest ignition timing you've reached at idle? I've only seen 2-4 degrees after adjusting the idle tables as the timing was in negative before that but could get more with VT.
    A work around is to lower the virtual torque in the idle area's and the ECU will then command more idle spark. But I too avoid any VVE or VT changes unless absolutely necessary. There is a thread on here somewhere where Higgs discussed the External Load and other idle tables. Find it and it may help point you in the right direction. If you idle spark is too low because you have a giant throttle body on then you might have to lower the Virtual Torque and VVE a little in that area since the air velocity slows down.
    Last edited by TriPinTaZ; 3 Weeks Ago at 12:19 PM.
    I've tuned a few things...

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    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Eng.LSX View Post
    What was the highest ignition timing you've reached at idle? I've only seen 2-4 degrees after adjusting the idle tables as the timing was in negative before that but could get more with VT.
    I had it idling at 25 at one point but now I keep it around 12.

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    Quote Originally Posted by TriPinTaZ View Post
    A work around is to lower the virtual torque in the idle area's and the ECU will then command more idle spark. But I too avoid any VVE or VT changes unless absolutely necessary. There is a thread on here somewhere where Higgs discussed the External Load and other idle tables. Find it and it may help point you in the right direction. If you idle spark is too low because you have a giant throttle body on then you might have to lower the Virtual Torque and VVE a little in that area since the air velocity slows down.
    Exactly that what I did to get the timing I wanted, yes it has 103mm TB. I'll look for the post thanks.

    Quote Originally Posted by Higgs Boson View Post
    I had it idling at 25 at one point but now I keep it around 12.
    That's great, well done.

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    Quote Originally Posted by Higgs Boson View Post
    I had it idling at 25 at one point but now I keep it around 12.
    It just sounds so much better that way lol
    2019 C7 ZO6 M7.

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    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by HeavyChevy305 View Post
    It just sounds so much better that way lol
    It will idle at 25 if I multiply the stock Torque Reserve table by .25

    It idles 12-15 if I multiply it by .35

    Pretty simple. But why does it do that?

    I guess I can only think the "Torque Reserve" is how much torque idle (torque management advance during idle conditions) will pull off your main spark table....? My main spark table is set to 30 degrees all around and at the idle cells.