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Thread: Need Some Knowledge - DFCO seems rather aggressive

  1. #1
    Tuner in Training
    Join Date
    May 2009
    Posts
    27

    Need Some Knowledge - DFCO seems rather aggressive

    I just re-enabled the MAF and VE functions on my file, (was running SD for a while until I got done tuning it) and I'm having some newfound issues.

    1. I reenabled the DFCO, and it seems pretty freaking aggressive, as it cuts timing down to 0 deg, sometimes negative, and ~17-19:1 AFR on decel. It never did that before, so I'm thinking something I changed must have affected it. You can see it in the attached photo and in the attached log at about the 1:40 mark.

    2. Also my fuel mileage seems to be rather horrible, about 250 miles/tank (~12mpg if I calculated correctly) which is down from about the normal 22mpg I'd get. I haven't really done anything but change the IFR and respective values for the LS7 injectors (I tried Motron 63lb/hr, but when I found out that I'd have to rescale the VE due to lack of solid data, I chose something that has more reliable data in my eyes) refine the VE table a little, and rescale the MAF due to the switch. I also get this ridiculously strong gas smell from the exhaust, which is why in the file attached, I was messing with the proportional fueling.

    3. Once I start to lean on it, the engine goes lean, like 17:1 lean and the engine stumbles badly. When it started doing this, the only thing I changed once this problem reared its head, was the fuel pump, trans, and converter. All those checked out, so that leads me back to the tune file, as the problem was never there before.

    Any Help would be greatly appreciated
    Attached Images Attached Images
    Attached Files Attached Files
    Last edited by LQ495DCMSS; 03-02-2014 at 06:18 AM. Reason: Added CFG file
    1995 DCM SS -
    Running: 6.0L LQ4, L92 Heads, LS3 Intake, Headers, Vogtlands, Billets, SS Brake Lines, BAER Fronts, Stealth and Prop Mod
    Staging: 0411 PCM,
    In the pits: EPS Custom Cam, 3.73s & Eaton Posi coming soon

  2. #2
    Potential Tuner
    Join Date
    Jan 2014
    Location
    Sumas, WA
    Posts
    6
    Your DFCO is doing what it's designed to do (Decel Fuel Cutoff) it's suppose to go lean. Although it does appear to be closer to the stock settings which doesn't amount to much of anything for DFCO. I believe the negative (retarded) timing is a sort of engine braking. You can change this by making the timing table "DFCO Entry Spark Threshold"...I changed mine to 12 degrees across the board. Next, your "Entry/Exit RPM vs Gear Enable" is a little high (this is what I meant by stock settings). Also, your "Exit Enable Map vs Baro" table can be increased by, oh say, 6 kpa, because when you're in decal it doesn't take even a few seconds for your MAP value to increase above 34 kpa which is when your DFCO is currently set to disable. There are multiple things in that menu window that enable AND disable your DFCO status. And I don't believe the "DFCO Clutch Transistions" is only with manual transmissions. And the "Stall" at the top of the DFCO window is your lower RPM limit. You can also lower your "Enable Temp" right above "Stall"...mine is at 104*F.

  3. #3
    Potential Tuner
    Join Date
    Jan 2014
    Location
    Sumas, WA
    Posts
    6
    And changing your injectors without having the proper settings in your calibration will have a HUGE affect on your fuel economy.

  4. #4
    Tuner in Training
    Join Date
    May 2009
    Posts
    27
    Thanks for the info. I knew I wasn't too crazy. I got the proper IFR, etc. for the LS7 injectors of one of the threads on here if i remember correctly. I'll give that a shot and see how she likes it. I just realized I didnt add the cfg file, so I've added that to the first post. I'm still trying to figure out this lean spike I'm getting from a dead stop. I'll keep working on it.
    1995 DCM SS -
    Running: 6.0L LQ4, L92 Heads, LS3 Intake, Headers, Vogtlands, Billets, SS Brake Lines, BAER Fronts, Stealth and Prop Mod
    Staging: 0411 PCM,
    In the pits: EPS Custom Cam, 3.73s & Eaton Posi coming soon