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Thread: L83 turbo MAX tq way off

  1. #1
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    L83 turbo MAX tq way off

    I am stuck, had this engine running great in a swap vehicle, excellent drivability and quite fast at 7.90 1/8 mile with 3.08 gears.

    After adding turbo and tuning MAF and VVE tables I end up with a max tq at about half engine tq at WOT and it is probaly getting worse when I increase boost. It opens throttle fully but during or after shifts it always closes to about 50%. Had the same issue without the turbo as soon as the max tq was lower than engine tq. I corrected it by changing the max torque timing table which actually increased max tq without a big increase in engine tq but now since the difference is huge that will not be enough.

    I read a lot about the virtual tq tables, question is what to log and base changes on? Engine tq vs predicted, airflow vs predicted or base changes on changes I made to VVE and MAF?

    Any other ways to deal with this without cheating and raising the VVE?

    Specs: -72 firebird with 2016 L83 and 6L80E. Running FPCM, Ethanol sensor but currently on gasoline, LT4 injectors and HP pump, 76mm BW S400E turbo, A2A intercooler, changed sensor config and running 3 bar TIAP sensor and TCIAP sensor, no cats, 2900rpm stall tq converter.

    Attaching tune, stock tune and log from today. Hoping for some good ideas on what to try next!
    Attached Files Attached Files

  2. #2
    Senior Tuner SultanHassanMasTuning's Avatar
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    did you do a breakout for the built in baro for MAF
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  3. #3
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    Quote Originally Posted by SultanHassanMasTuning View Post
    did you do a breakout for the built in baro for MAF
    Yes, TIAP is now a 3 bar LS9 type MAP sensor. For TCIAP sensor I used the stock 1 bar, added cables to the ECM. Actually the TCIAP should be the new source for baro, but I am not 100% sure since I have 2 different BARO values (in the log). VVE corrections responed well with this setup.
    Last edited by grandam75; 05-26-2020 at 01:34 PM.

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    Quote Originally Posted by grandam75 View Post
    Yes, TIAP is now a 3 bar LS9 type MAP sensor. For TCIAP sensor I used the stock 1 bar, added cables to the ECM. Actually the TCIAP should be the new source for baro, but I am not 100% sure since I have 2 different BARO values (in the log). VVE corrections responed well with this setup.
    I think the SAE one is correct, and the other is based on an estaimte from the MAP or something. Try disabling the BARO sensor tests. Under Engine Diag > Airflow max out the P2227 correlation pressures and the P0101 ECT values to stop those tests. It seems that with the new setup the ECU would still estimate BARO and then average the two values, which messes up the pressure ratio calc.

    As for Max Torque.. my actual torque is way above predicted also, but it seems to be fine..
    Last edited by MORLOK; 05-26-2020 at 02:53 PM.
    2014 Silverado L83 - Knockoff S366 Turbo - LT1 Fuel Pump and Injectors

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    I think you are both on the right track. I checked some logs and the pressure ratio is off compared to the sensor BARO reading. Strange thing is I cant find the baro PID hp tuners use for their PR calculation but is is somewhere between the 2 logged values.

    I guess there is no way to turn off baro updates? I would line to keep the TIAP sensing pressure.

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    Quote Originally Posted by grandam75 View Post
    I guess there is no way to turn off baro updates? I would line to keep the TIAP sensing pressure.
    Yes there is, i just told you how in the previous post. Disable the BARO sensor tests.. Then both BARO measurements should match.
    2014 Silverado L83 - Knockoff S366 Turbo - LT1 Fuel Pump and Injectors

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    Quote Originally Posted by MORLOK View Post
    Yes there is, i just told you how in the previous post. Disable the BARO sensor tests.. Then both BARO measurements should match.
    Damn, it works! Thank you!! Tried earlier today and it did not work at first, I did not fully max the values out, every value needed to be maxed out for this to work. I better read carefully next time =)
    Thanks again, will redo the VVE and get back with results.

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    That's great! Honestly, I didn't know that completely maxing the values was that important, I just got lucky when I tried it I guess. Good luck!
    2014 Silverado L83 - Knockoff S366 Turbo - LT1 Fuel Pump and Injectors

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    Quote Originally Posted by grandam75 View Post
    Yes, TIAP is now a 3 bar LS9 type MAP sensor. For TCIAP sensor I used the stock 1 bar, added cables to the ECM. Actually the TCIAP should be the new source for baro, but I am not 100% sure since I have 2 different BARO values (in the log). VVE corrections responed well with this setup.
    Which pins did you use on the ECM? Hoping to get this done on my truck this weekend, but the only pinout I could get ahold of has 2 TCIAPs (bank 1 and bank 2 for twin turbo). Wondering if I need to use the pins for bank 1, or if it doesn't matter. Thanks.

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    Quote Originally Posted by TytusTheGreat View Post
    Which pins did you use on the ECM? Hoping to get this done on my truck this weekend, but the only pinout I could get ahold of has 2 TCIAPs (bank 1 and bank 2 for twin turbo). Wondering if I need to use the pins for bank 1, or if it doesn't matter. Thanks.
    I used these pins:
    ECM X2 #45 Signal
    ECM X2 #64 5V
    ECM X1 #20 Low ref

    Small update. VVE tuned again and even though max tq does not reach engine tq there seems to be no limiting at shifts since the timing drop is enough for engine tq to go below max tq. Runs a lot better overall.

    One more thing I noticed. The max torque timing table does affect the torque values a lot and is really worth dealing with, especially if not running stock timing tables which I guess few people do. Does anybody know exactly what function it has on gen V engines? I read on earlier platforms it acts as an "urgency" table in some way, but in this case it seems very related to the VTT.

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    When I did it, I pinned it to a BARO sensor location I found from a ATS-V wire diagram. I don't have the pin numbers so I don't know if it the same pins that grandam75 used or not.

    Here is a link to my post, i was able to use pins and low ref all from the same harness.
    https://forum.hptuners.com/showthrea...l=1#post585966
    2014 Silverado L83 - Knockoff S366 Turbo - LT1 Fuel Pump and Injectors

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    From what I can tell you guys are using the same pins, so that's a good sign. Those are the ones showing up as Bank 2 on the CTS pinout I have, but doesn't seem to be an issue (maybe selecting single turbo (TC-TIAP-TCIAP) instead of TC-TwinGas in Sensor Config makes these the only pins active?). The pinout I have shows X2 #65 as the low reference, which will be nice because all three wires will be right next to each other. Hopefully I can get this done in the morning after I get off work. And thank you both for digging in and figuring this out. Maybe more of us can start implementing this now and have an easier time tuning these things.