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Thread: Pulling Timing under Boost

  1. #21
    Senior Tuner Ben Charles's Avatar
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    I won't be back at my computer for a few days...but with that pulley and no restrictive plate that car has to be in the 800rwhp mark then. I think the rear in tank pump is good for around 800rwhp on gas so on e55 I can see it running out of fuel. I think with the in tank pump resolved and since you have a lash caped lt4 fuel system it may do 800rwhp on e55 at 20mpa, just have to see where your at.

    From what I know the zo6 and stingray have the same rear pump and I've seen another tuner push 72x or so rwhp out of a stock z06 fuel system on e5x!!!

  2. #22
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    I'm having a similar problem with massive KR on a procharged C7. Spraying a ton of meth but have the AFR tuned in the 12's @ 15* timing. Plugs look very good. I even dropped the timing to -5 and still got the KR. Cannot find any causes of false knock. I feel your pain, I'm interested to see if you figure it out.
    2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.

  3. #23
    Senior Tuner Higgs Boson's Avatar
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    I figured it shows Knock Retard of 10 because that is what was in the Max Retard vs RPM table.

    I also figured out my Peak Torque table was set too low (even though I thought it was high enough). I raised it up and now the car has some power, but I haven't had time to get it back out to see if my fuel pump works now (side effect of bad torque model?)....

    I also went back to the stock VE table and set it to MAF only for the time being to see if the large GMVE numbers were throwing things off.

  4. #24
    Advanced Tuner Redline MS's Avatar
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    You ever notice that even though you are showing a KR value that the timing is not effected by the value of KR indicated.......this meaning you have commanded 15 degrees and you are indicated 4.9 degrees of KR yet the timing is still at 14.8-15. I think there is a hole in this knock control logic. When we first got our C7 in late 2013 we ran a tank of race gas to see if we could rid this reported knock.....surprisingly it didn't effect it. At that point you have to start wondering if it works as we think. This is turning into the same chase of throttle not going full open when at times it doesn't need to be open to effect output.
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  5. #25
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    Quote Originally Posted by Redline MS View Post
    You ever notice that even though you are showing a KR value that the timing is not effected by the value of KR indicated.......this meaning you have commanded 15 degrees and you are indicated 4.9 degrees of KR yet the timing is still at 14.8-15. I think there is a hole in this knock control logic. When we first got our C7 in late 2013 we ran a tank of race gas to see if we could rid this reported knock.....surprisingly it didn't effect it. At that point you have to start wondering if it works as we think. This is turning into the same chase of throttle not going full open when at times it doesn't need to be open to effect output.
    Sounds like there's another table adding timing , perhaps variable cam , ect , or iat. I'm curious what kind of knock sensing is being used on these motors. Is it the standard frequency/vibration type knock sensor from the LS , or is it something weird like a cylinder pressure sensor?
    2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.

  6. #26
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Redline MS View Post
    You ever notice that even though you are showing a KR value that the timing is not effected by the value of KR indicated.......this meaning you have commanded 15 degrees and you are indicated 4.9 degrees of KR yet the timing is still at 14.8-15. I think there is a hole in this knock control logic. When we first got our C7 in late 2013 we ran a tank of race gas to see if we could rid this reported knock.....surprisingly it didn't effect it. At that point you have to start wondering if it works as we think. This is turning into the same chase of throttle not going full open when at times it doesn't need to be open to effect output.
    Yes, it does hold commanded timing (for the most part) even though it shows retard, however, my Hi and Lo tables are the same right now, not sure if that is why. One issue I noticed while under the car, a header primary is literally resting against my "oil cooler." I guess it isn't affecting anything regarding knock since there is none at regular VE values.

    I only am getting this phantom retard over 1.0 Pressure Ratio......the more I obsess over it, the more I think it is a fail safe of sorts against failing fuel pressures. It will be a week or so and I will have a second fuel pump to mount on the tank and we will find out for sure. Until then, I am done with it.....rev limiter set to 3500.

    BTW, i have a 37% ethanol mix in there now and it carries slightly higher before nosediving. I am considering running it out of fuel and filling up with MS103 or the like and seeing if that will allow me to get to 7K, although I don't want to use race gas (or meth), the whole point of this build is E85.

    Quote Originally Posted by nkautz View Post
    Sounds like there's another table adding timing , perhaps variable cam , ect , or iat. I'm curious what kind of knock sensing is being used on these motors. Is it the standard frequency/vibration type knock sensor from the LS , or is it something weird like a cylinder pressure sensor?
    regular knock sensor, I haven't missed any spark tables.
    Last edited by Higgs Boson; 09-12-2015 at 09:10 PM.

  7. #27
    Advanced Tuner Redline MS's Avatar
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    Quote Originally Posted by Higgs Boson View Post
    Yes, it does hold commanded timing (for the most part) even though it shows retard, however, my Hi and Lo tables are the same right now, not sure if that is why. One issue I noticed while under the car, a header primary is literally resting against my "oil cooler." I guess it isn't affecting anything regarding knock since there is none at regular VE values.

    I only am getting this phantom retard over 1.0 Pressure Ratio......the more I obsess over it, the more I think it is a fail safe of sorts against failing fuel pressures. It will be a week or so and I will have a second fuel pump to mount on the tank and we will find out for sure. Until then, I am done with it.....rev limiter set to 3500.

    BTW, i have a 37% ethanol mix in there now and it carries slightly higher before nosediving. I am considering running it out of fuel and filling up with MS103 or the like and seeing if that will allow me to get to 7K, although I don't want to use race gas (or meth), the whole point of this build is E85.



    regular knock sensor, I haven't missed any spark tables.
    Are you chasing this KR with E85? At some point common sense and experience has to prevail over real or false knock. Once we use a knock limited fuel (if known to be good) and we run a spark advance that is in the sanity range...one can only conclude the KR is false and possibly induced from noise. At the end of the day the knock sensors are just microphones. The blower bolted to the block is most certainly something that can transmit noise to the knock sensors.

    It also would reason to make sense that GM would not use knock retard as a way to control spark except for detonation control. I mean there are a crap load of other tables in the controller to control spark every which way but Sunday.

    I'd be curious if you put some controlled fuel in the tank just to confirm all this.
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  8. #28
    Senior Tuner Higgs Boson's Avatar
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    I'm not chasing it at all, I am chasing the cause of the phantom retard, not necessarily knock.

    I have run E10, E55, E37 and it has been the same each time, again, only over 1.0 pressure ratio. the retard isn't doing anything to actual timing, it is just showing up in the knock regard pid.

    either way, under full throttle my fuel pressure nosedives at 3400-3500 rpms so that's the priority now.

  9. #29
    Advanced Tuner Road's Avatar
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    Sounds to me that your pressure ratio has exceeded the maf to pressure ratio calibration. That will cause limiting like you are experiencing.

  10. #30
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by Road View Post
    Sounds to me that your pressure ratio has exceeded the maf to pressure ratio calibration. That will cause limiting like you are experiencing.
    so what's the solution? I have 1.0 in the two fields under airflow. is there another place?

  11. #31
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    Did you disable / max out : Engine Diag -> P0068 ? Airflow Correlation
    2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.

  12. #32
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by nkautz View Post
    Did you disable / max out : Engine Diag -> P0068 ? Airflow Correlation
    Now we may be onto something! Thank you!

    I haven't changed anything in the Diag Airflow section and there are 3 or 4 places I need to. Derrrr......

    Going to see what's going on with that today! Thanks again.

  13. #33
    Senior Tuner Higgs Boson's Avatar
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    Well, the car runs great but I still have an unknown source of Retard (5 degrees due to Max Retard table) and still get commanded spark timing.
    It is at 2900 RPM and 1.04 g/cyl and 109 kpa (or thereabouts) and up. I have "perfect" throttle response, spark, fueling, etc below that.
    I am considering disabling the knock sensors (or at least measuring the voltage) to verify they aren't picking something up just for a short pull to 4500 (but I would think on E37 or E55 I would not have knock at such low boost (1 psi).

    Also, what fuel pressure should I expect just past and above the 3500-4500 range? I get 70 psi going into that max cylinder pressure range and it drops back to 50 (it was nosediving before) but I am still getting 19-20 MPa at the HPFP. I am not sure if disabling P0068 fixed the fuel pressure issue but I don't want to run it all the way up again just yet..... If 50 is normal for upper RPMs then I will give it another go....

    Here are a couple logs:
    c2.hpl

    c4.hpl

    Also, I still haven't gotten Max Engine Torque up yet, maybe that's the cause of the Retard issue.
    Last edited by Higgs Boson; 09-13-2015 at 12:45 PM.

  14. #34
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    I'm not logging fuel pressure so can't help you there but why not try another pull 1000rpm higher and keep one eye on the wideband.

    Edit: Didn't you say there was something touching the exhaust (false knock)? I've been tip-toeing through KR the whole time I've been tuning this car, it's scary not knowing for sure if it's real but I've been checking 2 spark plugs after every pull and they always looks great.
    Last edited by nkautz; 09-13-2015 at 03:33 PM.
    2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.

  15. #35
    Senior Tuner Higgs Boson's Avatar
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    One primary is touching the oil cooler which is a little metal box on the driver side rear of the engine. Since there is no sensor activity anywhere but under boosted load I am sure it is not causing an issue, not to mention it was an NA motor for almost a year with no knock.

    I need to jack the car up and remove a narrowband and put the wideband back in and run the harness, etc. About 30 minutes of work but it's hot and I am feeling lazy. ;-)


    Anyone else seeing (or even worrying about) Max Engine Torque? Mine shows 380 to 460 or so when Predicted is 8xx and Actual is high 6xx. Spark and throttle (and butt dyno) do not appear to be limiting.

  16. #36
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    Hmm , if you see an obvious source of vibration I would remedy that , at least temporarily put some header wrap right there in that spot. Might also try to to secure the narrowband when you remove it so its not dangling and rubbing against the exhaust, can also wrap that sucker in exhaust wrap. But yeah , I'm pretty sure my KR is also not vibration related, but dunno what else it could be. It's gotta be something about the n/a OS seeing boost.
    2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.

  17. #37
    Senior Tuner Higgs Boson's Avatar
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    I agree.

    I just remove the narrowband completely so its not banging anything. I have considered exhaust wrap, but again....would have to go to the store. played golf instead. :-)

    Time to go crawl around under the car and retest fuel pressure/finish tuning wot.

  18. #38
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    All my torque management and TCS settings are stock. Hasn't seemed to affect power, only reported TPS %. The driver demand tables just seem to be like a LS "Pedal position vs TPS" table, just changes the throttle curve. I played with them and then put them back to stock. When I mess with the TQ mngmt settings , shifting (A8) seems to get a lil bit sloppy.

    Edit: It's a 3bar SD tune
    Last edited by nkautz; 09-13-2015 at 06:15 PM.
    2001 Z06 : 856/830 : Built LQ9 403ci : D1SC 17psi : Self-built , self-tuned.

  19. #39
    Senior Tuner Higgs Boson's Avatar
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    Here are two more logs. Any ideas from anyone? I am definitely running out of fuel, not sure if the timing is related....it sure doesn't feel that fast. I guess it wouldn't with no timing in it.

    C1.hpl

    C5.hpl

  20. #40
    Advanced Tuner Road's Avatar
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    Quote Originally Posted by Higgs Boson View Post
    so what's the solution? I have 1.0 in the two fields under airflow. is there another place?
    Here is the table I was referring too. HP apparently hasn't mapped it yet.
    Attached Images Attached Images