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Thread: DFCO Question

  1. #1
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    Default DFCO Question

    So I had a thought about DFCO and had some questions.
    Until I got my wideband and program, I never knew much about DFCO and realize that in stock form it prob saved quite a bit of gas mileage when it was active. But as I modded the truck here and there I noticed that it seems to be not as precise in activating as it was before. Looking over settings and all I think I need to adjust some but not sure where to begin.
    I know one thing is I dont prefer it to be active before the eng op temp reaches a certain temp. Like when its too cold. With the exhaust being more open it pops more as I see DFCO engage in cold times of the year.
    Another thing is it seems on the highway to be less active when it should be. The stock rear gear ratio was 3.08 and I have 3.73 now. Since the RPMs in each gear cruising are directly affected by the gear swap, would the DFCO not be effected as well? Being a peramiter of maybe MAP entry or something need to be altered? And if so, would lowering it or raising it be the direction to go?
    I am learning but is it possible to log a MAP pid with a ?? pid to compare to?

    Thx for the continuing help!, Mike

  2. #2
    Lifetime Member EagleMark's Avatar
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    MAP and RPM are the only options I've seen in my OS. There's not much that can be done with the MPH setting it's enable, I'm stuck at DFCO off at about 40 MPH as that is when is disables but no Parameter for that...

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    Oh are you running a differnt OS than stock?

    The level it 'hits' when it engages seems kinda harsh. Prob gets best mileage that way but I find its too aggressive. Im sure playing with the Entry Ramp rate is where I need to adjust. Just gotta get time to play with it. I have quite a few peramiters I can play with.
    One other thing is, if I am in 4th gear cruising into town downhill, I am doing about 40-50mph, DFCO kicks in. But in 5th, same speed, DFCO does not. I am guessing the MAP changes due to the engine RPM and if I want it on in 5th (lower rpm) I need to adjust there.

    Kinda fun to learn and play with. Just nice to have other ppls input, experiences and expertise

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    Quote Originally Posted by Mikz86ta View Post
    Oh are you running a differnt OS than stock?

    The level it 'hits' when it engages seems kinda harsh. Prob gets best mileage that way but I find its too aggressive. Im sure playing with the Entry Ramp rate is where I need to adjust. Just gotta get time to play with it. I have quite a few peramiters I can play with.
    One other thing is, if I am in 4th gear cruising into town downhill, I am doing about 40-50mph, DFCO kicks in. But in 5th, same speed, DFCO does not. I am guessing the MAP changes due to the engine RPM and if I want it on in 5th (lower rpm) I need to adjust there.

    Kinda fun to learn and play with. Just nice to have other ppls input, experiences and expertise
    I switched from 01 Silverado LM7 auto to 02 f-body LS1 manual DFCO spark settings and it gave a much smoother transition into DFCO, so smooth I could barely tell it was in DFCO. But I went back because I like it more before. The aggressiveness doesn't both me. It appears that only DFCO spark can be adjusted and not fuel.
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

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    Yep, same on mine. Its spark ramp in and out rate adjustments and not fuel

  6. #6
    Lifetime Member EagleMark's Avatar
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    Good tips!

    The aggressive entry is noticeable but? What I'd like to tweak and not sure it's possible is the braking effect. If exiting a freeway it's fine, but if coasting down a mountain grade it can decelerate/engine braking so much my cruise would kick in and out. Maybe a TCC lockup change so TCC was unlocked? But this seems to let RPM down to close to idle and DFCO RPM settings... I'm still stuck with it only working to about 40MPH no mater what MAP and RPM settings I use.

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    My trips are short so very interesting about the cruise control issue. I would have to get out on the highway and see with mine.
    My entry rate seems aggresive (ie: engine braking effect harsh-ish) My issue is prob easy solved with some lightening on the entry ramp rate. I am guessing..
    I have a manual also..so no TCC Lockup with me.
    IIRC in DFCO coasting to a stop, it will turn off at maybe 30MPH...have to doublecheck

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    The engine braking effect might be adjusted by the Low TPS DFCO spark curve. Just guessing, but I'd think more spark in DFCO would help reduce engine braking. The braking can only be adjusted so much because the injectors are essentially shut off so the engine isn't making power anyways.
    2001 Silverado 5.3L ECSB 2WD T56:
    T76 turbo, Meth injection, 72# injectors, 799 heads, 212/212 114LSA cam, Built 4L80E, 3.42's
    EFILive V1 Commercial, COS5 2-bar SOLSD, AEM wideband

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    Mike, KIF from S10planet here. I don't have DFCO enabled on my truck any more. I'm pretty sure it is because of the marine throttle body which doesn't have that diffuser installed on it, but when I'm driving down the freeway, I'm barely touching the throttle, this was causing the DFCO to kick in/out under normal driving conditions. I started using lean cruise, but I found it easier just to adjust the AFR table instead of LC/DFCO.
    E85 is NOT flex fuel.

    2003 Chevy S10 4.3L LU3 LS1B Auto
    48 LB injectors
    Race Proven Motors 2114 intake
    T70 turbo.

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    Interesting. I have a CFM-tech blade without the difuser as well. I never realized a difference in DFCO with or without it. Then again I did the blade swap in 2004 or 2005...one of my first mods way back when.
    Maybe that is a TPS adjustment issue. Mine seems to work well with the exception of the harshness and maybe I can fiddle with the settings so DFCO comes in in 5th at lower road speeds. Then again, the road speed I may like as is giving me the option to be in 5th (lower rpm) but no DFCO at that particular road speed OR I can pull it back into 4th (rpms jump up a bit) and then DFCO will kick in at my command....basically.
    Explain what u did in the afr table

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