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Thread: Driver Demand

  1. #21
    Tuner in Training
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    Hello, I am in the process of tuning my stock C7 Z51 7sp for a few more horses. I have read the info on the E92 and how it uses tq. I have also read this thread and others on Gen V tuning.
    Can you elaborate on what you are doing to allow the car to accept/use the changes I have made to timing and AFR. I understand you have to modify the driver demand tables.
    However I do not understand exactly what you have done in this area and what my goal should be. If you increase Tq it wont help so what is our goal here and how do we achieve it?
    Any help clearing this up is greatly appreciated.

    Thanks

  2. #22
    Advanced Tuner Boost's Avatar
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    I will say this in an attempt to contribute: I was trying to make sure absolutely nothing limits me at WOT. So I raised Driver Demand to stupid high numbers in the last rows, the result was no additional power but a huge pedal lag and then sudden violent transition - almost as if the computer was creating it's own curve or adjustment for what I did. I did produce and verrry torque feeling tune by manipulating this table, but drivability has suffered and I've gotten used to driving around the snappy / laggy behavior.
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  3. #23
    Quote Originally Posted by Higgs Boson View Post
    If you raise Peak Torque too much it won't go into PE (if you use torque as a criteria). Since it uses Peak Torque to look at PE, I feel it must look at Peak Torque for other calculations as well so I basically smooth Peak Torque out and leave it alone....more 550 values smoothed to lower values at lower RPMs. Being stock and NA, it doesn't seem to be limiting anything.
    Yup i lowered the pe delay down to 5% and everything works well.. and it def seems the ecu is referecing this peak torque table for alot of stuff including trans tables.. shift pressures etc. The shifts were notably harder and felt better when raising these values

  4. #24
    lol at Higgs Bonson "don't rape your DD tables".. that's gonna be some truth for sure. I've been raping my DD tables all weekend just trying to fix 1 stupid problem. On friday I was convinced the driver demand tables were the answer, but now monday morning, I'm back to scratching my head.

    I might as well say this now, my name's not "Eddy"... So if I list my mods, Higgs and others will probably know who this is..... We just finished a monster cam install on my car. Already had full bolt ons w/ Kooks 2" headers, 3" orx, 3" PRT exhaust, Halltech CAI... so now the cam. Prior to the cam install I only had simply bumped my 100% line of Driver Demands up a bit to keep the throttle open. But now w/ the addition of the cam I've found myself playing w/ the part/low throttle numbers significantly trying to get rid of TqMgmt retard at part throttle that is making the car pop and bang for the first few seconds of normal acceleration from a dead stop. After the cars rolling it really doesn't seem to have a huge problem (still very active TqMgmt retard, but doesn't have significant effect on the way the car drives). So I've been focusing my time on the under 20 MPH numbers. With good results, but band aid type results IMO.

    It helped a LOT, but it also made the throttle response so damn touchy I could barely drive the car in traffic without losing my mind. So yesterday I went back to a much less aggressive approach on the DD tables, and it's back to driving like normal, but the damn TqMgmt retard is back to being intolerable.

    I'm not convinced DD is the end all be all fix to this problem. But it definitely helped when I "raped" the numbers. But you can't drive a car if the throttle is so sensitive between 0 and 4%. So now I'm on here seeing what others have found.. Which seems to be same as me. a whole bunch of not much...

    Also, side note... tuning idle on these things w/ no airflow tables is a learning curve. Apparently we don't even have separate idle spark tables anymore. The ECM just uses Tq/Mgmt spark to keep idle torque at the desired level.

  5. #25
    Advanced Tuner yonson's Avatar
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    I 100% agree the DD doesn't seem like the correct way, but until we have access to the parameters we need such as the actual or virtual torque tables, (from the looks of the coefficients we have access to, they will be virtual) "raping" the DD seems to be the only way currently... Is the cam you installed still a VVT cam? If it is still VVT you are going to have to tweak the VVT parameters, hopefully you got some baseline logs with the factory cam that you can compare to your current cam.

  6. #26
    Quote Originally Posted by yonson View Post
    I 100% agree the DD doesn't seem like the correct way, but until we have access to the parameters we need such as the actual or virtual torque tables, (from the looks of the coefficients we have access to, they will be virtual) "raping" the DD seems to be the only way currently... Is the cam you installed still a VVT cam? If it is still VVT you are going to have to tweak the VVT parameters, hopefully you got some baseline logs with the factory cam that you can compare to your current cam.
    It's VVT w/ a cam phaser limter. I've made best power with the tables all zero'd out though.

    I've actually got my car running pretty damn good with raped DD tables. On stock cars or even cars w/ superchargers, WOT DD raping should be the only thing people need to mess with. But changing the actual volumetric efficiency of the motor certainly throws everything out of wack. I'm still getting a little TqMgmt retard at part throttle, but I think by the end of the day after only messing with DD tables it will be pretty clean.

    Sure sounds good. Here's a couple vids of the car.

    http://www.youtube.com/watch?v=OQW0G...lkGz5A&index=1

    http://www.youtube.com/watch?v=pxLT-...&feature=share

  7. #27
    Senior Tuner Higgs Boson's Avatar
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    I actually ended up going back to stock DD tables except for raising the 100% row to like 500 or something. i started getting random surges in power at part throttle.

    I decided to change my logging procedure for ETC and found that if I use Average and measure ETC Avg Pedal / ETC Position it almost always averages out to 1.0 which means that I am getting my requested blade opening "in the long run." If I only use "+" to log the values then most of the upper part of the table will show I need higher values. So I am going to leave the DD table stock for now with the exception of the 100% row and that is only if the log shows less than 100% throttle blade opening.

  8. #28
    Yeah, on a stock or bolt on car the 100% row is the only thing you need to be messing with. W/ internal engine mods, better bring a big box of band aids for your tune.

  9. #29
    Advanced Tuner yonson's Avatar
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    Quote Originally Posted by FastEddy View Post
    It's VVT w/ a cam phaser limter. I've made best power with the tables all zero'd out though.

    I've actually got my car running pretty damn good with raped DD tables. On stock cars or even cars w/ superchargers, WOT DD raping should be the only thing people need to mess with. But changing the actual volumetric efficiency of the motor certainly throws everything out of wack. I'm still getting a little TqMgmt retard at part throttle, but I think by the end of the day after only messing with DD tables it will be pretty clean.

    Sure sounds good. Here's a couple vids of the car.
    Yeah, for WOT close to 0 will almost always make the best power, I was meaning down low during cruise loads tweaking the VVT parameters can help on your surging etc... For DD below 28% throttle and 62 MPH the most I've changed it is -6 to +2 from stock to get the best feel (which is quite subjective).

  10. #30
    Senior Tuner Higgs Boson's Avatar
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    Isn't "0" 7 degrees advanced? I thought WOT makes more power with cam retard....? Can you elaborate?

  11. #31
    Quote Originally Posted by Higgs Boson View Post
    Isn't "0" 7 degrees advanced? I thought WOT makes more power with cam retard....? Can you elaborate?
    Actually that does raise an interesting question I had. The stock numbers seem a little strange. I don't have a tune in front of me, but obviously low load areas have a considerable amount of advance built into the phaser. Then WOT it starts out around like 2 or 3 then works it's way up to like 10 at peak rpm. Assuming these are positive numbers, I thought 10 at peak seemed pretty a$$ backwards. So I was curious if these numbers in the tune actually represent cam timing "advance" or if positive numbers possibly are negative in reality? It's kind of like TqMgmt advance in the scanner is showing positive numbers, but in reality are negative numbers.

    And in my very limited experience tuning the VVT on gen 5's it has always yielded considerable losses on the dyno. It's almost like you want the cam phaser to be stationary under WOT, even though GM obviously doesn't have it stationary at WOT in the stock program... for whatever reason, if you try doing things that "make sense" in cam timing theory, it just makes the power curve look like crap and a loss across the board. But again, very limited effort on my end has been put into messing with the VVT. We degree'd my cam in where we wanted it. Played with it a little on the dyno, but didn't gain anything, just made the power curve look like crap. So left it at "0".

    The car pulls to 7200 clean as a whistle. http://youtu.be/Dpqq2ndq_iA

  12. #32
    Quote Originally Posted by yonson View Post
    Yeah, for WOT close to 0 will almost always make the best power, I was meaning down low during cruise loads tweaking the VVT parameters can help on your surging etc... For DD below 28% throttle and 62 MPH the most I've changed it is -6 to +2 from stock to get the best feel (which is quite subjective).
    I'm definitely going to give that a try. I'm still not super satisfied with the touchy throttle I have. I'm just running p-v so tight that I don't have much room to work with.

  13. #33
    Advanced Tuner yonson's Avatar
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    Quote Originally Posted by Higgs Boson View Post
    Isn't "0" 7 degrees advanced? I thought WOT makes more power with cam retard....? Can you elaborate?
    Sorry, I was meaning 0 in HP Tuners, I'm not sure what the actual cam specs are, so it very well could have that much advance ground in. I haven't tried any negative values yet, our car seemed to be most happy around 2 at WOT.

  14. #34
    Quote Originally Posted by yonson View Post
    Sorry, I was meaning 0 in HP Tuners, I'm not sure what the actual cam specs are, so it very well could have that much advance ground in. I haven't tried any negative values yet, our car seemed to be most happy around 2 at WOT.
    With the stock cam? Mine has 4 degree's advance so at 0 on the phaser I was fairly surprised it pulled so flat all the way to 7200.

    Still think it's a bit bit strange the stock tune has more cam advance up top (under WOT) than it does down low. cam timing.jpg

  15. #35
    Senior Tuner Higgs Boson's Avatar
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    It doesn't those are retard numbers. You subtract those from the park position which is at or around 7, depending on the engine (LY/LS/LT/etc).

    So 0 = 7 (advance) and 10 = -3 (retard)

    cruise areas have a lot of retard for emissions and economy (egr effect).

    what I have not seen is what people change these to to make more power.....like changing the 8-10 values up top to like 20 or something. all i have seen is zeroing out the cruise areas for power but that doesn't make sense to me anyways because hitting the throttle will raise airmass out of that area anyways....

    you can't advance the cam past 0 (like using -5 to acheive 12 degrees of advance), 7 is it....

    talking about stock cam here
    Last edited by Higgs Boson; 05-20-2014 at 11:34 AM.

  16. #36
    Advanced Tuner yonson's Avatar
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    Damn, that's totally backwards from how you would think it would work...

  17. #37
    Quote Originally Posted by Higgs Boson View Post
    It doesn't those are retard numbers. You subtract those from the park position which is at or around 7, depending on the engine (LY/LS/LT/etc).

    So 0 = 7 (advance) and 10 = -3 (retard)

    cruise areas have a lot of retard for emissions and economy (egr effect).

    what I have not seen is what people change these to to make more power.....like changing the 8-10 values up top to like 20 or something. all i have seen is zeroing out the cruise areas for power but that doesn't make sense to me anyways because hitting the throttle will raise airmass out of that area anyways....

    you can't advance the cam past 0 (like using -5 to acheive 12 degrees of advance), 7 is it....

    talking about stock cam here
    Damn, so it really depends on where you're installed at. Just because it's 7 degree's advanced in the park position on the stock cam won't mean that w/ aftermarket. Now I really wish i degree'd my stock cam to see where it was at. We're 112 LSA at 108 ICL w/ my current cam.. so technically wouldn't park position be exactly that? Or does it move when it's powered on?

  18. #38
    Tuner DWC's Avatar
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    Ben,
    Give me a call or email when you get a chance.
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  19. #39
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    Delivered Engine Torque.hstPredicted Engine Torque Cmd.hstActual EngineTorque.hstDriver Pedal Requested Axle Torque.hst


    seems like HB and a minority want to actually do the work to figure out the torque model.

    now, ive created a few 'demand' and 'delivered' histos that may be of use in all of this to figure out what is going on.

    i havent made up anything for peak torque yet but heres the stuff i came up with. add, comment, ask, etc..

    im thinking some sort of comparison between peak torque and demand, requested, and delivered is called for.

  20. #40
    Quote Originally Posted by Higgs Boson View Post
    so I have taken to the driver demand table corrections by pasting the error between "ETC average pedal" vs "ETC position" much like one would do with afr error.

    I multiply only the positive error to open the throttle more where it is less than pedal. i multiply by the full percentage rather than half as it corrects more slowly than afr does.

    it works, the discrepancy is very small to nonexistent now and the feel is great. I have found that all of the areas that need improvement are above the 45% pedal areas so it won't affect low throttle feel like highway cruising or idling or parking lot use.
    Thanks for the info. I have been trying to set up a histogram for the driver demand table as you describe. I have the axis set up to match my dd table and I'm logging the channels that you mention above. Im struggling on how to track the error in the chart. Do I have to set up a math or function to calculate the error between average pedal and etc position? Any guidance would be greatly appreciated!