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Thread: Help with tune - seems to be down on power by ET/MPH

  1. #1
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    Help with tune - seems to be down on power by ET/MPH

    Vehicle specs - 2005 Silverado 1500 RCLB 4800 lbs race weight 6.0/4l80/4.56 rear 4000 ish stall converter 305/50/20 (32" tire)

    Engine has 317 CNC ported heads, LQ9 flat tops 228/232 .635/.635 cam, TBSS intake 90mm TB 1 7/8 headers

    All my bench racing experience says that this engine should make 500ish hp, but ET/mph says it's making 375-400 hp. Was thinking it would be a full half second faster than it is - this is the best out of three runs - no spinning off line - foot brake to 3200-3400 rpm other two runs were 13.3 nearly identical

    60 1.95
    330 5.489
    660 8.432
    660 mph 83.52
    1000 10.967
    1320 13.142
    1320 mph 103.28

    I got in a bind last year when I was putting truck together and paid a dude to help me with tune - so a lot of the engine setup was done by him, but I ended up getting set up to do it myself after he left the 4l60 stuff in the ECU and my transmission burnt up, so this is my first attempt at tuning a factory GM ECU.

    Question is, what am I missing? Tune and 13.1 run from Darlington attached. Of note I have the dual channel Zeitronix wb O2 sensors and A/F data from them should be in there.

    Thanks,
    Ryan
    Attached Files Attached Files

  2. #2
    Tuning Addict 5FDP's Avatar
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    Those really heavy wheels/tires will slow you down, it takes a lot of power just to get those moving.

    One bank is far leaner than the other and both are still off of the commanded AFR. One bank it running damn near 14.0 for a good part of the run.

    I'd personally run it a little richer and a little less timing. Like 12.5-12.7AFR and 25-27 degrees of timing. Very possible that a dyno would show that it's not gaining anymore power or maybe even losing power at 30 degrees of timing.

    I'd make sure that you are not dropping fuel pressure and tune your VE table too.

    You can also raise up the max torque vs rpm so that isn't holding anything back and you could max out the ETC TPS MAX so pcm doesn't limit the throttle opening.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  3. #3
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    Why MAF-only? How was WOT tuned, by the MAF or by PE? WBs are consistently leaner than commanded (and never dip down richer), and the commanded is already leaner than I'd run it.

    What injectors and what fuel system? 'Cause you have an IFR table set up for referenced/return, and then Offset vs Volts vs Vac set up for returnless.

    Spark is kinda high.

  4. #4
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    I didn't do any WOT tuning other than play with the AF ratio compared to the WB to try to dial it in. Not 100% on what I'm doing.

    Injectors are 42lb @43.5 psi but running with a corvette filter/regulator at 58 psi - I'm looking at redoing the fuel system ahead of some more upgrades in the future - Bigger lines - return regulator

  5. #5
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    What injectors? What part number? Where did the data come from? You need data that matches the physical injectors, and set up properly in the file, before anything else.

    It could stand to be a nearly a full point richer (actual, not commanded, since MAF/VE's not been tuned yet) with 5* less timing and I bet it'd pick up 80-100ft-lb.

  6. #6
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    https://fuelinjectorconnection.com/p...lb-ls2-l92-lq4

    FIC 42lb drop ins

    Will try less timing and more fuel and report back - not sure I will get same weather again until fall though.

    Thanks for the help so far

  7. #7
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    Your injector flow rate table is one value all the way across. You have a fixed 58psi rail pressure. You have constantly variable pressure in the intake runner from changes in throttle opening, load, engine speed etc. Suck harder on the outlet of the injector while the pressure at the inlet remains the same and flow through the injector will increase. Your injectors do not flow the same amount of fuel with 0kPa vacuum (WOT, atmospheric) as they do at 80kPa vacuum. The IFR table needs to let the computer know that this flow rate is not constant, so it can make the right calculations to deliver the right amount of fuel.

    Assuming the IFR at 58psi is accurate, it would look something like this when corrected:

    screenshot.22-05-2022 07.39.27.png

    (lowering the manifold pressure (increasing the vacuum) has the same affect on injector flow as raising rail pressure by the same amount)

    Without the data supplied with the injectors I can't tell you if the other data is correct or not, only that the Offset vs Volts vs Vac table is configured correctly for a fixed, non-referenced fuel supply.

    I have not looked at much else in the file, these basics need to be sorted out first.

  8. #8
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    Defintely need to change some things first before you do any tuning. You are logging too much data in the scanner, only log what you need. Your long term fuel trims are adding about 10% and its still very lean at that, target 12.5 afr or .85 lambda for now, i would recommend lambda. Make sure that you have all of the correct injector data input before you do anything. As mentioned already, the data is wrong for your fuel system and timing is too high. You need to take some timing out, 30 degrees is too much, start with 22-24 degrees and measure the gains on a dyno or at the track. You are also commanding 2 degrees more timing in the base timing adder, another 2 degrees of timing will be added their once you command a richer afr so zero that out for now. You need to recalibrate your maf and ve models. I would start out with a stock 6.0 maf calibration rather than adjusting the one you have, its very wavy and needs to be smooth and linear, start out by adding at the top of the maf curve so you dont run lean. Only real way to calibrate the maf and ve is on a dyno with an eddy brake at steady state so you can accurate data.
    2000 WS6 Trans Am LS3, Tick Performance Stage 2 cam, ARH 1 7/8" Headers, FLT Level 6 4L60e, Circle D 5c Launching on a 200K 10 Bolt

    2001 Camaro SS M6 Black on Black