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Thread: DFCO Not Working

  1. #1

    DFCO Not Working

    I believed the previous owner had it set to not go into decel cut so that it burbled on decel. While I'm OK with that in first gear, I would like decel cut to do it's thing and I cannot figure out why it's not working.
    My parameters for DFCO all appear to be good when I compare my map to other stock LS1 maps. My AFRs stay around 12-13 on decel.

    2001 Corvette_with_Procharger_MAF_changes.hpt
    • 2001 C5 Corvette (625rwhp - Procharger, LS6 heads, Torquer V2 cam)
    • 1991 Volvo 940 - 2JZGTE (600rwhp - PT6466, HKS 272 cams)

  2. #2
    Tuner awest623's Avatar
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    Can you post a log file along with the timestamps of when you want DFCO to trigger?

    I need to see these values:

    Throttle position
    Engine rpm
    Vehicle Speed
    Equivalence Ratio Commanded
    Wideband Lambda/AFR (if you have it)
    Engine Coolant Temp
    Barometric Pressure
    Manifold Absolute Pressure
    Cylinder Airmass
    Timing Advance
    Fuel system #1 status
    Fuel system #2 status
    Throttle Cracker Airflow
    Throttle Follower Airflow
    Idle Air Control Valve Position
    1998 GMC K1500 Z71
    * L31 350 Vortec
    * AUS 43lb injectors
    * Comp 08-410-8 with 1.6 rockers
    * P59 swap
    * Whipple supercharger
    * JBA headers
    * AFR 190cc heads
    * NV4500 swapped
    * Cal-Trac traction bars
    * 1" blocks, 265/70r17 BF Goodrich KO2s, 17X8.5 ALPHAEQUIPT COMMAND LT

  3. #3
    Sure thing, I just so happen to have a great example from the other day.
    Look around the 4:14 mark. You can see I disabled cruise control and began to decel, and just to get some TPS triggers, you can see I blip the throttle a few times, once for a downshift.
    FWIW, the same conditions exist whether cruise was enabled or disabled.

    29-mar-2023-2.hpl

    EDIT: I just realized that even though the Accel Pedal is 0%, the Throttle is still ~10%. Perhaps Throttle Cracker is preventing DFCO? Although that doesn't fully make sense, because the Throttle Cracker is calling for about 1.5 g/s in that part of the table, and the MAF is showing well above that.

    EDIT2: I glanced over this one parameter a few times and now realize that I don't think I'm ever hitting the Entry limit, and that's the MAP. I'll have to raise the Entry/Exit parameters and give it a shot today.
    Last edited by phuz; 03-31-2023 at 07:40 AM.
    • 2001 C5 Corvette (625rwhp - Procharger, LS6 heads, Torquer V2 cam)
    • 1991 Volvo 940 - 2JZGTE (600rwhp - PT6466, HKS 272 cams)

  4. #4
    Tuner awest623's Avatar
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    Got a chance to take a peak at it.

    I noticed a couple things:

    o Your DFCO entry vehicle speed it pretty high, not a factor in this log but I would personally drop the speed down to something like 15mph

    o On the ETC engines I don't know if the Enable TPS table is referencing the Accelerator Pedal or the Throttle body itself. Perhaps try disabling the throttle cracker to drop the MAP and Throttle Body Position in decel. As a warning, disabling the throttle cracker may cause your engine to stumble/die when coming out of gear after decel, your results will vary.

    o For your first edit: Your throttle follower output seems correct. The MAF will not align with the throttle follower value ever, air is still gonna make its way into the engine. The throttle follower is just adding to that.

    o Your enable RPM is too high. Just from the log you provided you'll never hit the RPM DFCO trigger because it has to be above 2100 RPM. I'd suggest lowering the RPM entry/exit to 1200/1000.

    I'll attach 3 tune files for you to try out.
    o The first with throttle follower disabled
    o The second with throttle follower enabled and the MAP trigger raised
    o The third with throttle follower enabled, MAP trigger raised, and throttle trigger raised

    EDIT: you need to raise your DFCO stall too, right now it won't execute stall recovery until it's below your idle RPM
    Last edited by awest623; 03-31-2023 at 08:08 PM.
    1998 GMC K1500 Z71
    * L31 350 Vortec
    * AUS 43lb injectors
    * Comp 08-410-8 with 1.6 rockers
    * P59 swap
    * Whipple supercharger
    * JBA headers
    * AFR 190cc heads
    * NV4500 swapped
    * Cal-Trac traction bars
    * 1" blocks, 265/70r17 BF Goodrich KO2s, 17X8.5 ALPHAEQUIPT COMMAND LT

  5. #5
    Tuner awest623's Avatar
    Join Date
    Oct 2019
    Location
    Pyeongtaek, South Korea
    Posts
    70
    Well it won't let me save changes to the tune file, so here's exactly what I'd change:

    1st tune file:
    o Throttle cracker enable speed: 255 mph
    o Throttle cracker disable speed: 254 mph
    o Throttle cracker airflow: zero out the table
    o DFCO Stall: 900 RPM
    o Vehicle Speed vs Baro: 15 mph across the board
    o Enable RPM vs Gear - Entry: 1200 rpm across the board
    o Enable RPM vs Gear - Exit: 1000 rpm across the board

    2nd tune file:
    o Throttle cracker: all stock values
    o DFCO Stall: 900 RPM
    o Vehicle Speed vs Baro: 15 mph across the board
    o Enable RPM vs Gear - Entry: 1200 rpm across the board
    o Enable RPM vs Gear - Exit: 1000 rpm across the board
    o Enable MAP vs Baro - Entry: 43 kPa across the board
    o Enable MAP vs Baro - Exit: 48 kPa across the board

    3rd tune file:
    o Throttle cracker: all stock values
    o DFCO Stall: 900 RPM
    o Vehicle Speed vs Baro: 15 mph across the board
    o Enable RPM vs Gear - Entry: 1200 rpm across the board
    o Enable RPM vs Gear - Exit: 1000 rpm across the board
    o Enable MAP vs Baro - Entry: 43 kPa across the board
    o Enable MAP vs Baro - Exit: 48 kPa across the board
    o Throttle Enable TPS: Add 9 percent across the board

    Let me know how it works out or if you have any questions about why I'm recommending these changes.
    1998 GMC K1500 Z71
    * L31 350 Vortec
    * AUS 43lb injectors
    * Comp 08-410-8 with 1.6 rockers
    * P59 swap
    * Whipple supercharger
    * JBA headers
    * AFR 190cc heads
    * NV4500 swapped
    * Cal-Trac traction bars
    * 1" blocks, 265/70r17 BF Goodrich KO2s, 17X8.5 ALPHAEQUIPT COMMAND LT

  6. #6
    Ah, I didn't get a chance to incorporate these changes yet, but I did fix my Entry/Exit MAP yesterday and voila...it works!
    I'll take some of your other recommendations into account as well. Thanks for taking a look at this. Now I can go back to my thread of fighting my idle issues.
    • 2001 C5 Corvette (625rwhp - Procharger, LS6 heads, Torquer V2 cam)
    • 1991 Volvo 940 - 2JZGTE (600rwhp - PT6466, HKS 272 cams)