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Thread: Need help with tuning 2016 Camaro 2SS Manual with LT4 Engine

  1. #21
    So I got the wideband hooked up and I am in the process of trying to validate the stock LT4 VE settings.

    I created a speed density tune with the following modifications:
    - Disabled the MAF.
    - Disabled COT Protection.
    - Disabled LTFT by setting Min ECT to 491.
    - Forced open loop by setting the o2 readiness voltage to -2000 mV.
    - Set the Open Loop Gas EQ Ratio's to 1.0 across the board.
    - Disabled DFCO by setting the enable temps to 284 degress F.

    I let the car warm up using the regular tune and then switched to the speed density tune. I started the car and it doesn't idle great. The stoich AFR is 14.1, the commanded AFR is 14.1, and the wideband reads the AFR at 14.8 to 15.0. With slight throttle (850 RPM or so), the commanded stays at 14.1 but the wideband jumps to 16.0+.

    Out of the 3 stock LT4 tunes I have, the virtual VE tables are identical for 2 and the other is very close. I'm having a hard time believing my VE config is that far off considering I have a motor, airbox, etc. that's identical to the CTS-V.

    I've read that a vacuum leak may be the cause, but I'm not aware of anything that would be leaking.
    A previous post mentions camshaft angle, for now I still have stock settings. I wasn't sure if this could be skewing the AFR that much at idle or not?

    What other factors am I not considering?

  2. #22
    Senior Tuner Ben Charles's Avatar
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    14.1 will most likely show up at mid 14's (14.68 normal stoich ratio of pure gas) on your WB, so 14.8-15.0 would only be around 3% off which is acceptable...

    Start dialing in the Fuel, don't worry what FACTORY tables say...

    For what its worth I did the LT4 swap on an LT1 a little while back (probably the first?) I made a post about it on the corvetteforum.

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  3. #23
    Quote Originally Posted by Ben Charles View Post
    14.1 will most likely show up at mid 14's (14.68 normal stoich ratio of pure gas) on your WB, so 14.8-15.0 would only be around 3% off which is acceptable...

    Start dialing in the Fuel, don't worry what FACTORY tables say...

    For what its worth I did the LT4 swap on an LT1 a little while back (probably the first?) I made a post about it on the corvetteforum.
    Help me understand why the wideband would be off that much. I could see a small amount of open air throwing the sensors off when mounted at the tailpipe, but I had bungs installed for the widebands before the cats.

  4. #24
    Senior Tuner Ben Charles's Avatar
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    The WB reads stoich to whatever it is set too.... It has no clue to what it's set in the ECU

    If you had pure e85 in that engine and the stoich was 9.8, wideband still going to read 14.68

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  5. #25
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by travislambert View Post
    Help me understand why the wideband would be off that much. I could see a small amount of open air throwing the sensors off when mounted at the tailpipe, but I had bungs installed for the widebands before the cats.
    The wide bands aren't off, the formula your wb controller uses to convert lambda to afr is just different than other conversions.

    That's why you should be tuning in lambda and throw afr out the window.

  6. #26
    That makes perfect sense. The wideband was just showing AFR out of the box so I went with it not thinking about the fact that my stoich is not the same as what the wideband is configured for. I'll just use lambda.

    Thanks guys.

  7. #27
    Testing at idle/low RPM with the wideband I observed something interesting.

    With the Z06 VE Coefficients and the speed density tune described in a previous post, the idle isn't perfect but the wideband reads close to 1.0 lambda until I ease into the throttle. When the throttle is touched, it goes lean quick (1.15 lambda or so @ 850 RPM). Since it was going lean with slight throttle I shut it down and didn't attempt to drive it.

    With the CTS-V VE Coefficients and the speed density tune, it idles better. At idle it sits at about .94 lamda. On a short low RPM drive, the values stayed mostly steady except during throttle transitions.

    I plan to go for another drive tomorrow to confirm by pulling some higher RPMs, but it seems that the CTS-V VE Coefficients match up reasonably well other than the constant rich offset. Maybe the numbers are in tolerance, but I'm thinking there could be a coefficient somewhere skewing the airflow metrics. Does anyone know what this might be?

    I'm still a little unclear on how the following are applied and what the impact might be while SD tuning:
    Engine->Airflow->Electronic Throttle->Throttle Area Limits->Max Area
    Engine->Airflow->Electronic Throttle->Throttle Area Limits->Pressure Ratio Limits

    I know you guys are eager for me to start plugging new values, but I'm not comfortable with that yet and I can't help but to keep trying to figure out these stock tunes. The moment I start trying to modify VE coefficients, etc. the stock niceties like DoD go out the window. There has to be a way to get a mostly stock LT4 tune to work reasonably well and I am determined to find it. My current approach is an attempt to validate stock settings using the same approaches used to tune from scratch. Hopefully I can find the discrepancy. I am willing to pay any professional tuner that can help me make this happen. Just send me a private message and we can work out the details.

  8. #28
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    Engine->Airflow->Electronic Throttle->Throttle Area Limits->Max Area set to either your tune defaults or 100% across the board
    Engine->Airflow->Electronic Throttle->Throttle Area Limits->Pressure Ratio Limits defaults could be .9, set to 1 or higher....read the caption at bottom of screen while hovering over item

    1 or higher when maf is disabled, so it continues with business as usual

    as stated by some in the know, these gen 5's don't like to have sensors not hooked up or disabled.....my son's truck won't enable cruise while in maf disabled mode

    not the greatest idea, but as I said earlier, open loop with maf = once the maf is close (set maf to take over at 1000 rpm ), at least the car should run well everywhere

    remember that you are using a tb and maf sensor, NOT from the lt4, so at least the maf hertz values could be way different

    edit: set max pressure ratio to your max boost expected...probably 1.5 or higher...return to .9 after tune is good
    Last edited by rjw; 09-10-2016 at 09:25 PM.
    2003 MY Z06 3.3 liter whipple ...sold at around 1000 rwhp
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  9. #29
    Thanks rjw.

    The range on the "Pressure Ratio Limits" is showing a max of 1.0 so I'll try setting it to 1.0 from 0.9 tomorrow. That may be just what I need to get the AFR a little closer using the CTS-V VE coefficients.

    The "Max Area" is still a little fuzzy. I'm using the throttle body that came with the LT4 crate engine, but I believe it's identical to the LT1's throttle body on the Gen 5's. The part that's confusing is the Camaro SS, CTS-V, and Z06 all use different values for this setting. While testing I've mostly been using the value corresponding to the VE coefficients(i.e. if I'm using the Z06 VE values, I use the Z06 max area.) It seems as if the factory is using this for tuning rather than a fixed configuration value for a particular throttle body. The value certainly has a significant impact on the air/fuel calculations which is mainly why I'm trying to get to the bottom of how it works and how it's tuned.

    As for the MAF, the sensor itself is the same among the 2016 Camaro SS, CTS-V, Corvette Stingray, and Corvette Z06 (GM #22895480 (and the newer revision #23144941)). Of course the diameter of the tube it's placed in effects the configuration, but I believe this diameter is common at least among the Camaro SS and CTS-V (I'm actually using the CTS-V inlet duct). Unfortunately I'm not lucky enough for the stock camaro ss and cts-v MAF configurations to be alike. Even after interpolating to the same hertz values, the config is a little different in spite of the common sensor and duct diameter. Hopefully this will be easy to dial in once I get a reliable VE worked out.

    Thanks again for your post. Every bit of knowledge gets me that much closer.

  10. #30
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    you can just type 1.5 or 2 and say yes to warning message

    max area is lower than 100% IF you want to limit tb opening, for example is you have no traction when you punch it down low...try 100% until you get it tuned

    go to engine-airflow-dynamic-dynamic airflow and you'll see high rpm enable and disable if they are at say 4000 and 3800. set them to 1000 and 800 and...you'll be in maf only mode from 1000 rpm and up. use the cts maf airflow table or the Camaro one and tune the maf in open loop. hope you know how to set up open loop, no stft's either and set up a graph using maf hertz vs rpm. also make sure your rpm values match in the tune to the scanner.

    if not search and you should find.

    if you feel that things are lean, increase maf table in tune by say 1.2..always better to go from rich and lean out, except the o2 and wb sensors won't like SUPER RICH for very long. wb o2 sensor can go south quickly when way to rich

    remember that my input is just a bandaid to try to get you at least running....

    listen to Higgs and Ben....I was asking similar questions a month or 2 ago....lol
    Last edited by rjw; 09-10-2016 at 10:56 PM.
    2003 MY Z06 3.3 liter whipple ...sold at around 1000 rwhp
    wip 2015 Silverado w/2.9 Whipple (phase 1 completed) phase 2 in the works

  11. #31
    Senior Tuner Ben Charles's Avatar
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    The prediction coefficients need some adjusting sometimes when VVE tuning (or I always do), otherwise you may see "transit" fueling issues.

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  12. #32
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    Hey Ben...

    If I am feeding this guy misinformation, please let US know

    thx
    2003 MY Z06 3.3 liter whipple ...sold at around 1000 rwhp
    wip 2015 Silverado w/2.9 Whipple (phase 1 completed) phase 2 in the works

  13. #33
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    Quote Originally Posted by Ben Charles View Post
    The prediction coefficients need some adjusting sometimes when VVE tuning (or I always do), otherwise you may see "transit" fueling issues.
    any links to how to do this...I might be having some issues...thx
    2003 MY Z06 3.3 liter whipple ...sold at around 1000 rwhp
    wip 2015 Silverado w/2.9 Whipple (phase 1 completed) phase 2 in the works

  14. #34
    There is some information here, but not a clear method for tuning.

    http://www.hptuners.com/forum/showth...n-Coefficients

    The biggest problem I have with my tune is an attempted hard acceleration from lower RPM using a higher gear so I'm thinking the prediction coefficients might be a major source of the issue.

    In this log, 127 Sensor Config NA-MAP.hpl, there are two instances back-to-back starting at about 09:34:46

    I'm in 3rd (or maybe 4th) gear going about 40MPH, running in closed loop, with about 40 degrees of timing advance. When I quick transition to WOT, there's a sudden spike in the delta between Mass Airflow and Dynamic Airflow, Knock Retard shoots up, and my timing drops negative all while boost is quickly climbing.

  15. #35
    The stock 2016 LT1 and LT4 tunes have what appear to be purposely engineered values for VE modes "Manifold Switch Closed" and "Manifold Switch Open". To my knowledge there is no manifold switch on theses engines. Is there an alternate condition that may cause the ECM to switch from one mode to another? Which is the primary table?
    Last edited by travislambert; 09-11-2016 at 05:32 PM.

  16. #36
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    Open is primary - others there only if GM uses them from the factory... Just make open and closed the same if you don't have manifold runner controllers...
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  17. #37
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    are you using the vette tune knock sensor parameters? Might want to try the parameters from YOUR car oem tune. I find that the lt4 vette high octane spark table is a bit high for OTHER vehicles....might want to try the cts one if that car is heavier...also, stick with the lt4 SOI base table....I gained 20 rear wheel torq across the board ( 5.3L, but with lt4 cam)

    not advisable, but some change the minimum spark table to avoid the minus 10 timing, but it is a sign that something isn't right
    2003 MY Z06 3.3 liter whipple ...sold at around 1000 rwhp
    wip 2015 Silverado w/2.9 Whipple (phase 1 completed) phase 2 in the works

  18. #38
    Quote Originally Posted by rjw View Post
    are you using the vette tune knock sensor parameters? Might want to try the parameters from YOUR car oem tune. I find that the lt4 vette high octane spark table is a bit high for OTHER vehicles....might want to try the cts one if that car is heavier...also, stick with the lt4 SOI base table....I gained 20 rear wheel torq across the board ( 5.3L, but with lt4 cam)

    not advisable, but some change the minimum spark table to avoid the minus 10 timing, but it is a sign that something isn't right
    On my current tune, nearly everything including the knock sensor configs, spark timing, etc. is based on the CTS-V. I'm thinking those knock sensor configs should work out once everything else gets dialed in. I'll hold off on using any less sensitive settings until I rule out everything else.

    I got a chance yesterday using my speed density tune (MAF disabled, etc.) to check the CTS-V VE configs a little more thoroughly. Low RPMs stay pretty close to 1.0 Lambda, but RPMs above 2-3k they trend to 0.80 (steady state with 0.999 lambda commanded).

    I've requested access from HP tuners support to these parameters (http://www.hptuners.com/forum/showth...ficients/page3)

    [ECM] 34971 - MAP Estimated Max: Estimated maximum MAP value.
    [ECM] 34972 - MAP Estimated Min: Estimated minimum MAP value.
    [ECM] 12003 - Intake Manifold Volume: The volume of the intake manifold.

    Given that my Camaro OS was intended for a naturally aspirated engine, I would imagine my stock values for these are too low and potentially throwing off everything. Hopefully there aren't too many more hidden parameters skewing the tune.

    At the end of the day I realize I'll probably end up doing a custom tune. I just want to understand the stock tunes the best I can and dial in anything that's obviously wrong before tweaking too much. I would love it if I could get the stock VE coefficients to work with only minor tweaks. I went ahead and ordered the HP Tuners MVPI professional interface to make it easier to log the wideband and make corrections to the VVE tables. This way I won't have to hack my A/C pressure sensor or anything.

  19. #39
    So I have the VE coefficients fairly close where the car runs and drives okay using only the speed density tune. Most cells are within a percent or two of the commanded. However, it doesn't idle great and stalls if you don't give it a touch of gas while warming up.

    To check up on progress I decided to plug my VE coefficients back into my regular tune. Using those VE coefficients the car starts and then immediately stalls. There is no chance to give it a little gas to keep it running. Placing the old VE coefficients back in, it starts and runs just fine.

    I bumped up the virtual ve table values up around the low RPM / low manifold pressure thinking maybe it was too lean, but that didn't seem to help. Am I missing something or is it normal to need to fabricate the vve tables around the edges?

    151 2016 Camaro SS LT4 - Will Run.hpt
    151 2016 Camaro SS LT4 - Wont Run.hpt

  20. #40
    Nevermind. I got it going.