How does DFCO work in your car? - Fuel Economy, Hypermiling, EcoModding News and Forum

drewb · 07-16-2011, 12:48 AM

I have an AT (Ford AX4n in a Mercury Sable) and it only does DFCO when decelerating from 60 mph or higher. It shuts fuel off around 53 mph and then resumes fuel injection at 40 mph.

I wish it would remain off longer, but the little bit helps. How does DFCO work in your car?

SentraSE-R · 07-16-2011, 03:27 AM

My 2002 Nissan Sentra SE-R entered DFCO when deceleration started in gear with the engine >2500 rpm. That was effectively >65 mph in 6th gear, making DFCO pretty useless on that car.

My 2006 Scion xB enters DFCO if the engine is running >1500 rpm when deceleration starts. That's ~35 mph, making DFCO much more available and usable with the Scion.

My wife's 2006 Hyundai Elantra lacks DFCO.

camopaint0707 · 07-16-2011, 04:04 AM

I only have it on my cobalt which I don't exactly use for hypermiling. But it seems to work fine. Usually around speeds over 40mph in 5th. Actually I might have it on my acura or f150 but I have never checked.

jedi_sol · 07-16-2011, 06:01 AM

In my 1994 Acura Integra, pretty much anything higher than 1300rpm and faster than 25mph while in gear (verfied via mpguino)

alvaro84 · 07-16-2011, 06:58 AM

Teresa is not a car, but I can tell you that DFCO doesn't kick in at the low revs where I would normally use it to stop acceleration on steep downhills. Good that motorcycles have kill switches so I can force DFCO.

JethroBodine · 07-16-2011, 08:47 AM

On my '90 Jetta( Digifant Injection), the DFCO seems to be more dependant on the speed of the deceleration than actual RPM or vehicle speed. MPGuino has shown that even in a cold engine, DFCO can kick in when shifting and at low revs if going down a steep enough hill.

Drewb- a manual cut off switch would let you FCO for as long as you want(love mine).

drewb · 07-16-2011, 08:54 AM

I have been doing some casual research on an injector cutoff switch. I really like the idea and want to do that. I can't find a lot of information about doing that with an automatic transmission. Would it be any different than adding an injector cutoff in a manual? My concern is with the restart.

It seems like the ECU just turns the injectors back on and that resumes the engine. If you have any resources on this, I would really appreciate it. Thanks!

Joenavy85 · 07-16-2011, 09:14 AM

I finally got my Jeep to cut the injectors off yesterday, driving home I engine braked by first taking it out of OD, and then down to 2nd gear. This popped the RPM up to about 2800, and the injectors cut off until RPM was down to around 2300-2400, at which point I popped it into first which sent the RPM up to 3400, once the injectors cut off this time the RPM instantly dropped to around 2800-2900 (since the TC wasn't locked any more) and the injectors cut on around 2300-2400 as before. This is the first time I've gotten the Injectors to cut off, and while it's good to know that they do, the High RPM needed makes it basically useless for everyday driving. Luckily, I have a kill switch rigged up to the injectors to allow me to kill them as needed for engine braking.

Joenavy85 · 07-16-2011, 09:16 AM

Quote:

Originally Posted by drewb

I have been doing some casual research on an injector cutoff switch. I really like the idea and want to do that. I can't find a lot of information about doing that with an automatic transmission. Would it be any different than adding an injector cutoff in a manual? My concern is with the restart.

It seems like the ECU just turns the injectors back on and that resumes the engine. If you have any resources on this, I would really appreciate it. Thanks!

I have an Automatic and all I did was install a relay to interrupt power to the injectors, with a safety switch and momentary push-button to activate the relay.

Arragonis · 07-18-2011, 02:10 PM

This answers a question I was about to post. I have swapped from a 1.9 TDI 4cyl to a 1.0 Petrol 3 cyl and wondered about DFCO not working in some scenarios - instead of 9999 on the SG2 I can still get 150-300 MPG ratings on the overrun. The TDI would go to 9999 at any engine speed over idle.

However from reading this I think I may be driving the petrol too much like my old TDI at low revs, and expecting it to be the same. And there also seem to be min and max DFCO rpms to consider.

This is more complex than I thought