DFCO

[ace996]

I'm sitting on the fence with HPT, debating on taking the plunge or just going for a mail-order tune.

One such feature of the mail-tune is "lightened flywheel". The car is a CTS-V, and they suffer from slow rev-down on shifting/decel...either due to the massive duel-mass flywheel or due to GM's emissions programming...I think.
As discussed with many owners, the engine hangs between manual shifts and the only way to shift smooth is to shift "with patience". It's very evident when at rest and one revs the engine, the engine revs don't settle down without pause...as if fuel is still being added on throttle-lift.

My question...

Using HPT, what's needed to properly dial-in a crisp throttle-response/crisp decel? Is there a point at which DFCO can be dialed out too much, as in the car engine-braking too much and unsettles the rear-end on decel entering a turn at a track?

I hope I explained this clearly, I appologize if I have not.
Thanks,
ace

[jimmyblue]

DFCO -cuts- fuel, this sounds more like the throttle
cracker / follower or whatever the electric throttle
equivalent is. There are several features in HPTuners
like how much airflow to add, above & below MPH,
decay rate and so on. Lot of funny stuff about drive
by wire that I mostly have nothing to do with, except
the occasional truck session.

[03Quadrado]

Hey ace. Ive changed the throttle cracker and throttle follower on my 03 Silverado. My trucks throttle used to "hang", but after changing some of the settings, I was able to get my throttle to act just like a cable driven throttle. I love it now. Ps: saves a little fuel too. Lo. Pss: Jump down off the fence and come on over!

[WS6FirebirdTA00]

i disable dfco

[ace996]

I appreciate your replies, thank you. There's soo much to learn, and I'm really overwhelmed with it all. There are a few issues I know I can modify with HPT, like fans,o2sensors,TM...but the DFCO I don't really understand, yet. Ws6, you say you disable it...why? What does a disable do?

Again, I appreciate your help and look forward to joining the journey.
-ace

[WS6FirebirdTA00]

i disable it becuase when it was kicking in it was making the car act kinda strange. i had to chnage some settings in there but didnt feel like it lol. only thing it does is cuts off fuel on decel if you are in a certain rpm range and map range. i honestly dont see it saving much of any gas, might but i dont see a big impact on it.

[ace996]

Oh, saving gas isn't the goal...it's getting the car to react to throttle changes more directly and having the flywheel feel "electronically" lightened. Not a whole lot of info/guidance relating to this issue, I guess its just gonna come down to trial and error, huh? I just hope the error doesn't make a "BOOM"!!!
-ace

[WS6FirebirdTA00]

if you turn off dfco it wont hurt a thing, most of the time you dont even go into this anyway

[S2H]

if you turn off dfco it wont hurt a thing, most of the time you dont even go into this anyway

you go into DFCO quite easily....
pretty much every time you let off the gas at anything above 2K RPM and Above 25KPA it enters DFCO

turning off DFCO doesnt really hurt anything...but you wont get any decent engien braking with it off
people turn it off cause they get popping when the push in the clutch and are decelerating....but its usually just a bad DFCO Clutch transition going on that they need to tune out..

[WS6FirebirdTA00]

well with the stock settings in there my car never hit the limits to enter dfco with the cam. i adjusted it to come into play but it was causing more trouble than anything IMO so i just shut it off lol

[ace996]

Good answers, and certainly something I'm going to need to learn. I just placed my order with HPT so I should be clueless in about a week!!!!
I look forward to this journey, and certainly will need some help.
Thanks,
ace

[oztrack]

I want to maximize the use of DFCO - it saves fuel and makes a big difference in this area. Has anyone enabled it so that it works for longer when we are off the throttle.

[brh26]

Oztrack, Yes I have increased the DFCO entry rpm. Not a big change but I am taking things slowly. I have seen an improvement in fuel economy in my A4 with 3.91 gears of approx 1l/100km on the highway and 80kph zones. I only drive on the highway, so can't tell you what benefit there is in a city cycle.

[sikhabib]

I have set my car to go into dfco as everytime tps = 0

rpm entry 610 and exit 611 rpm (stall rpm 680) car idles at 600rpm stock cam
Map anything under 80 kpa
speed 1 kph

I do alot of city driving and i am for ever stopping at traffic lights or caught up in heavy but moving traffic. it does save alot of petrol and also brakes as the engine does alot of the braking so if i im coming to a stop or slowly cruising down a hill behind a car i dont have to keep tapping the brakes.

I used to get poping out the exhaust when coming out of dfco but that was cause timing is advanced to 10deg atdc (stock value) and that was igniting the fuel when exhaust valve was open. i changed this to 5 deg btdc and i never get poping at all now.

i also sped up the rate that it enters dfco by increasing the spark decay value so its pretty much instanaious once you take foot off accelerator

I have no driveabilty issues and no problems returning or staying at idle
Its feels alot like driving a carby car

[oztrack]

Thats awesome. I hadnt considered being that extreme - i bet it would save alot of fuel !

Can anyone confirm that there are no engine damage issues having it use DFCO more. I guess hardlu any fuel or timing means a cool engine - so it should be OK.

[EC_Tune]

Ace,

Back to your original q. I usually drop the throttle Cracker at RPM's above 1600 to 0 as this closes the throttle more on an ETC vehicle during deceleration (Electronic Throttle Control). BTW: the DFCO suggestions do help fuel economy. Reducing your o2 sensor switch points at cruise will help fuel economy as well. Kind of like "lean cruise".

Sounds like you are more interested in road racing your CTS-V. MPG is definitely not that important although unsettling the rear of the car is.

DFCO shouldn't unsettle the car as you will be in deep decel during braking and then you will be back on the gas as you enter the apex to power out. DFCO is more of an emissions / fuel economy improver.

EC