No fuel cut with engine braking?

[IndyIan]

My Focus doesn't seem to cut fuel with engine braking, my scangauge will show a total cut on the Tracker but the Focus somehow manages to burn nearly 2L/100km rolling down a hill?
Sad thing is that it uses less gas idling while coasting out of gear...
Anyone else with a scangauge notice their car doesn't do a proper fuel cut? Or is my Focus playing tricks on my scangauge?

 

[RobertISaar]

no.... seems like a ford thing. 92 ranger 2.3/5 speed RARELY drops into DFCO and when it does, it's only for a couple seconds at a time.

meanwhile in a 95 monte carlo with an automatic(with a tweaked tune, of course, i can't leave anything stock), i'm able to bump into DFCO at least as much as the ranger.

 

[SwampSurvivor]

Did Ford have DFCO fully implemented by then? It's hard to get the exact conditions that it requires. I can feel mine "kicking" in and out.

 

[RobertISaar]

i don't see why they couldn't have... GM had it figured out by 1987 in every application.

it takes quite a hill and some decent speed to get it active for more than a second or two in 5th gear. in 4th, it's a little better, in 3rd, it's overactive.

 

[HerrStig]

Originally Posted By: RobertISaar
i don't see why they couldn't have... GM had it figured out by 1987 in every application.

it takes quite a hill and some decent speed to get it active for more than a second or two in 5th gear. in 4th, it's a little better, in 3rd, it's overactive.

 

[HerrStig]

Originally Posted By: RobertISaar
i don't see why they couldn't have... GM had it figured out by 1987 in every application.

it takes quite a hill and some decent speed to get it active for more than a second or two in 5th gear. in 4th, it's a little better, in 3rd, it's overactive.
Volvo was doing it in the early 70's with Bosch EFI. Just a couple of extra contacts on the throttle position sensor.

 

[OVERKILL]

Originally Posted By: HerrStig
Originally Posted By: RobertISaar
i don't see why they couldn't have... GM had it figured out by 1987 in every application.

it takes quite a hill and some decent speed to get it active for more than a second or two in 5th gear. in 4th, it's a little better, in 3rd, it's overactive.
Volvo was doing it in the early 70's with Bosch EFI. Just a couple of extra contacts on the throttle position sensor.


And Ford's EEC-IV system (mid 80's) was developed in conjunction with Intel and Bosch.

 

[dparm]

It's not that Ford doesn't know how -- their engineers have decided not to do it for whatever reason. They didn't just arbitrarily say, "Meh, let's not cut the fuel." It's intentional.

 

[440Magnum]

Its probably an individual car design issue. DFCO will rapidly drop the temperature of the catalyst, so I suspect that as emissions regs continue to tighten, relatively few vehicles from the last couple of years will really do the prolonged fuel cuts on extended downgrades that we saw in previous vehicles. One of my previous cars would actually show a drop in coolant temp below the normal range on really long downgrades, and I always suspected that emissions would be abnormally high for a few seconds after getting back on the gas. It may be that the Focus, for some reason, needs a little fire all the time to keep the emissions systems churning so there's not a big surge of HC, CO, or NOx when the demand comes back after deceleration.

Side-note- you can HEAR the DFCO on my Challenger. It rumbles and pops out the tailpipes like an true old muscle car on deceleration for a second or so until the DFCO cuts fuel, then it gets quieter... so naturally I try to keep it from cutting by gently massaging the grumble pedal. ;-)

 

[IndyIan]

I assume it's to keep the cat hot, and it does seem to stop engine braking. It doesn't have drive by wire, but does maintain speed perfectly when the AC kicks in and out by adding a bunch of fuel without me moving the throttle. I'm getting 33-34mpg but expected a bit better and these fuel wasting strategies are a bit annoying.
Eager little motor though, just a little thirsty.

 

[brandini]

Originally Posted By: 440Magnum
Side-note- you can HEAR the DFCO on my Challenger. It rumbles and pops out the tailpipes like an true old muscle car on deceleration for a second or so until the DFCO cuts fuel, then it gets quieter... so naturally I try to keep it from cutting by gently massaging the grumble pedal. ;-)

I had a Magnaflow Cat-back on an 06 Mazda6 auto and when I engine braked to slow down it did the same thing. I LOVED it.

As for how to get it to kick in more? Check for vacuum leaks and make sure your pcv is properly working. My Mazda6 wouldn't do it ALL the time but it seemed to be load related so coasting from 50mph yes, coasting from 25 in too high of a gear- no.

 

[Rand]

my subaru will do it but only when decelerating over 3k(IIRC) in gear.

its for emissions that it doesnt totally cut it when coasting.

 

[KrisZ]

This would explain why my gas mileage stays the same despite me doing some heavy engine braking. I guess I'll just coast to stop lights from now on.

 

[Hokiefyd]

Both of our cars cut the fuel pretty aggressively. The instant mileage bars peg at the top and there's a lot of engine braking. Like driving an MT car. I do like it; cars with automatics that don't cut fuel seem to want to roll forever and you have to use more brake.

 

[dparm]

Originally Posted By: KrisZ
This would explain why my gas mileage stays the same despite me doing some heavy engine braking. I guess I'll just coast to stop lights from now on.



Engine braking supposedly helps rings seat (and maintain that seat). I would still recommend doing it occasionally.

 

[sciphi]

Both our cars do it. The Cruze needs to have specific conditions for on-command DFCO, though. Fortunately my driving can take advantage of forcing DFCO on command. It'll stay in DFCO for a long time. Longest I've seen is 90 seconds when going down a particularly long hill.

 

[IndyIan]

Originally Posted By: sciphi
Both our cars do it. The Cruze needs to have specific conditions for on-command DFCO, though. Fortunately my driving can take advantage of forcing DFCO on command. It'll stay in DFCO for a long time. Longest I've seen is 90 seconds when going down a particularly long hill.

How does the on command DFCO work? Part of your tune?'

 

[BearZDefect]

Originally Posted By: Hokiefyd
Both of our cars cut the fuel pretty aggressively. The instant mileage bars peg at the top and there's a lot of engine braking. Like driving an MT car. I do like it; cars with automatics that don't cut fuel seem to want to roll forever and you have to use more brake.

I agree, and I like fuel cut. The vehicles I've owned since EFI became standard all did it after the engine had warmed up and the vehicle's momentum would turn the engine at least 1,200rpm. But a recent dealer software update in the Sonata removed the fuel cut from 3rd gear. There is no TCC lock in 3rd in this car, but it would still slow down before. Now it will continue with engine pushing it at the same speed without me touching the go pedal. It's very annoying to have to brake so much more in slow traffic. On level ground, the vehicle should gently slow down when I release the go pedal.
While I understand what 440Magnum wrote about keeping the cat hot, as IndyIan wrote:
Originally Posted By: IndyIan
...these fuel wasting strategies are a bit annoying.

 

[Palut]

I've got a 2013 Focus ST and it's the same way. It uses about .45 gal/hr while coasting in gear, which is about the same as is used idling.

 

[SteveSRT8]

BearZDefect's post shows how wildly the programming affects this. Obviously varies hugely by platform.

Wait till cars update themselves wirelessly.