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

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...

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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Originally Posted by Mikz86ta

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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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.

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

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.

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

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.

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.

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

I don't have my laptop here with me in afghanaland, but there is a table in COS3 that you can use to change the AFR for load/rpm. I set up the freeway cruising areas and high vacuum areas leaner than the rest of the table.

Ahh ok, yea I dont have the experience yet for the COS's

For the record.....if in DFCO (I was in 4th gear and allowed it to engage coasting downhill) and I cruised to slowing down, it turned itself off at 25mph. I need to check my settings on that. I am guessing thats the 'MPH to allow dfco to occur' setting. I wanna see if 25 is exact my setting or if hysteris has to do with it. I dont really understand hysteris settings.

BTW, most conservative driving with some spirited heavy right foot a few times a week.....I am getting a solid 16mpg on the trucks trip/data display. Got it up to 16.5mpg a week ago super conservative driving. Again, I work 10 miles from home, and colder mornings with my 180* stat, my eng operating temps get there just shy of my work. So relatively on a daily basis (Mon-Sat my work days) I have short trips. Id prob avg better mpg if I had longer trips per drive.

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Originally Posted by Mikz86ta

I dont really understand hysteris settings.

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I wish someone could explain the hysteresis settings, they are confusing me as well, so I left them stock.

Thaks for your continued service KIF. Hope you make it back safe and soon from the big sandbox :) !

Its kinda like 'history but thats about all I understand really

I remember now why I changed 3314 to 25mph......cause when I would be cruising thru the neighborhood (esp in the cold mornings) or thru a parking lot, DFCO at lower speed enable as it used to be would kick on. Causes alot of exhaust pop-pop-pop with my very free flowing exhaust. Was annoying. Figured 25mph was typically the highest speed I would ever go in those situations.

I dont know the difference in 3309 and 3318 since they both say RPM Enable
As well as 3310 and 3320 which are both MAP Enable settings. Tho 3320 has both enable and disable graph and settings.

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Originally Posted by ferocity02

I wish someone could explain the hysteresis settings, they are confusing me as well, so I left them stock.

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I will have to think about this more in terms of DFCO....but, for the time being, here is a definition in terms of tuning in general that explains it. RPM and Rev Limiter is easier to understand since most of us have hit the limiter before in RPM



its basically the time/units needed to activate or deactivate something...the actual definition of it is

The lagging of an effect behind its cause,

but i doubt thats what your looking for, but as an example lets say your talking about the rev limiter. Lets say the hysteresis is 300 rpms well If the rev limiter is set to 6300, once you hit that even with your foot to the floor the engine will not attempt to rev again until 6000 rpms. 6300-300(lag time)=6000 hope that explains it for you.

Ok, that's kinda what I thought too. It's like a buffer.

The description in EFILive is...

DFCO RPM Hysteresis: Engine speed must remain above {B3318} "DFCO RPM"(Enable)-this value to enable DFCO.
DFCO MAP Hysteresis: Manifold pressure must remain below {B3320} "DFCO MAP"-this value to enable DFCO.

I understand your example, but for DFCO you can specify the enable and disable MAP and RPM, so it appears the hysteresis's are not needed??

The description gives me a headache...

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Engine RPM must be above the "Enable" value to enable DFCO.
If DFCO is active and engine RPM falls below the "Activate/Deactivate" value, then DFCO is deactivated.

When all of the DFCO enablers are met, hitting any DFCO activate level will turn on DFCO. After DFCO has been enabled hitting any DFCO disabler or hitting every DFCO deactivate will turn off DFCO.

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If you look at Enable/Disable and Activate/Deactivate which is very confusing! Change the way you look at them to Enable and Disable it works well.

What are some of the DFCO Paremeters referring to? M6? Manual Trans? Looks like all mine are off...

Although my {B3314} is all set to 15KMH I never get any DFCO till after 40 MPH and if in DFCO it disables at 40 MPH? Maybe I have a VSS setting off? Although all stock and auto trans maybe something in M6 is preventing any DFCO below 40 MPH?

I'm running basically stock 01 Silverado 5.3L 12208322 settings with some adjustments to the RPM and MAP curves. You can find the stock tune on tunefiledepot.

I agree the description is a bit confusing, but here is my take... Enable means DFCO is "armed" but not running, as in not cutting fuel or reducing spark. Activate means it's armed and cutting fuel and spark.

In order for DFCO to arm, you must satisfy ALL the enablers for ECT, VSS, RPM, TP, and MAP. Then for DFCO to activate you must satisfy EITHER the RPM or MAP activate/deactivate level.

According to the description you have to satisfy both the RPM and MAP deactivate in order to deactivate DFCO. However, I have found that you only have to hit one or the other to deactivate DFCO. In my setup I usually hit MAP deactivate first.