Page 1 of 2 12 LastLast
Results 1 to 20 of 38

Thread: DFCO question

  1. #1
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47

    DFCO question

    M6 car. In gears 1-3, DFCO works fine. In 4-6, it doesn't seem to want to enable. The map readings are similar in decel in each gear (~19-21 kPa). The RPM/speed/TPS/MAP entry values are all met.

    In 4th gear, ~2800 RPM, I let off the throttle and IPW flatlines to ~2 ms, spark is pretty stable and drops slowly as the RPMs fall, but it never enters DFCO. AFR goes rich.

    Is there something else I should be looking at here?

    base_rtt_ol_new.hpt

  2. #2
    Advanced Tuner
    Join Date
    Nov 2015
    Location
    In a sandpit
    Posts
    444
    Possibly Transient > Min Fuel (mg). Usually that has to be lowered if you want the injectors to go under around 2mS, at least in older cars/ECUs like mine. Mine is .028, and the AFR will goto way over 22:1 in DFCO (thats my chosen way..).
    99 TA, Texas Speed LS376, PRC heads, 233/239 cam, Fast 92mm, 95mm TB, card style MAF, Tick TR6060, Strange 4.11 12 bolt axle & clutchpack diff, Strano springs/dampers, Vette 18" wheels, Vette disks, CTS-V calipers, 16lb flywheel, long tube headers, no cats.

  3. #3
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    I upped transient fuel a bit to try to smooth out lean spikes in between shifts, which worked.

    To be clear though, when DFCO engages, IPW goes to ~0.5 and my wideband pegs lean. In the example I gave in the OP, I was explaining what was happening in higher gears when DFCO wasn't kicking in.

  4. #4
    Advanced Tuner
    Join Date
    Nov 2015
    Location
    In a sandpit
    Posts
    444
    Well, I don't recall there's any other setting lurking anywhere, mine will kick in in any gear, so long as I meet the 'rules', lol.

    EDIT: I see my TPS values are a bit higher than yours at the higher RPM, of course it also depends if the TPS is setup & reporting ok, mine does not always goto 0% when I shut off but to e.g. 0.7 or similar. I have a cable throttle of course...
    Last edited by dermotw; 09-18-2016 at 09:44 AM.
    99 TA, Texas Speed LS376, PRC heads, 233/239 cam, Fast 92mm, 95mm TB, card style MAF, Tick TR6060, Strange 4.11 12 bolt axle & clutchpack diff, Strano springs/dampers, Vette 18" wheels, Vette disks, CTS-V calipers, 16lb flywheel, long tube headers, no cats.

  5. #5
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    I grabbed a log I can post later, but TPS looks fine at 0.0% and .53v, which are the same values as when I can get it to enter DFCO in lower gears.

  6. #6
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    dfco_cut.hpl

    This is just a quick snip from the log, but it starts in 4th gear, then I toss it into 3rd, where it seems to go into DFCO. Wideband is ~12.5:1 in 4th, ~2.0ms IPW, then ~15.87:1 and 0.5ms in 3rd.

  7. #7
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    Any thoughts on what else might be causing this?

  8. #8
    Advanced Tuner
    Join Date
    Nov 2015
    Location
    In a sandpit
    Posts
    444
    Well... I'm a bit confused by the log! Everywhere that you are deaccellerating you are at around 15:1, and your advance is low, so thats DFCO. Of course, there's no DFCO at the points where you aren't perceptibly slowing down?
    99 TA, Texas Speed LS376, PRC heads, 233/239 cam, Fast 92mm, 95mm TB, card style MAF, Tick TR6060, Strange 4.11 12 bolt axle & clutchpack diff, Strano springs/dampers, Vette 18" wheels, Vette disks, CTS-V calipers, 16lb flywheel, long tube headers, no cats.

  9. #9
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    Not sure what you mean? From 06.832-14.151, I'm in 4th gear and off the throttle. That was down a slight grade, which is why speed is increasing a little bit, but TPS/speed/MAP/RPM thresholds have all been met and instead of going into DFCO, it's rich at ~12.50:1. When I tap the throttle and downshift into 3rd at 14.161, you can see from 15.511+ timing starts to drop, the AFR starts to peg lean, and it's in DFCO.

    I found a similar problem here. After PM'ing the OP asking if it was ever resolved, I received this response -

    "Something in the ECU, that is not able to be accessed by either EFI live, or HP tuners is preventing the '04 GTO ECU from using DFCO in gears 4-6. No idea why."

    Could someone from HPT possibly chime in here to confirm or deny this?

  10. #10
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    To update this -

    I tried flashing the original, non-RTT/enhanced OS (just to attempt to rule out some sort of OS corruption) with no luck. I can't think of anything else that would cause my issue? Anyone see anything similar before?

  11. #11
    Tuner in Training luke's Avatar
    Join Date
    May 2014
    Location
    PERTH WA
    Posts
    49
    I have the same issue but im assuming mine is due to the T56 conversion im still using the auto harness with only the P/N switch by-passed

  12. #12
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    Quote Originally Posted by luke View Post
    I have the same issue but im assuming mine is due to the T56 conversion im still using the auto harness with only the P/N switch by-passed
    Does yours work in any gear?
    Last edited by FD3S; 11-18-2016 at 05:53 PM.

  13. #13
    Advanced Tuner
    Join Date
    Feb 2016
    Location
    Texas
    Posts
    534
    Post #1 gears 1-3 DFCO works fine

  14. #14
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    Sorry, should've quoted. I'm the OP. I was curious if Luke had functional DFCO in any gear.

  15. #15
    Advanced Tuner
    Join Date
    Feb 2016
    Location
    Texas
    Posts
    534
    Damn I really need to start paying attention. Lol it must be Friday or something.

  16. #16
    Tuner in Training luke's Avatar
    Join Date
    May 2014
    Location
    PERTH WA
    Posts
    49
    Sorry for late reply it seems to only work in 1st and 2nd? weird I know because the only sensor the pcm has to go on is the VSS.. It goes way rich in every other gear 11:1afr on decell

  17. #17
    Tuner in Training luke's Avatar
    Join Date
    May 2014
    Location
    PERTH WA
    Posts
    49
    Ill earth the P/N wire today sometime and let you know how the DFCO reacts

  18. #18
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    Awesome, thanks.

  19. #19
    Tuner in Training
    Join Date
    Aug 2015
    Posts
    11
    has this been updated? working on this for my 04 V
    would be nice to get it fine tuned like the gen 5s see. 22:1 when you let off gas

  20. #20
    Tuner in Training
    Join Date
    Apr 2016
    Posts
    47
    No updates from me, the car is parked for the winter. Not sure if Luke did any other testing.