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-   -   DFCO questions (http://www.fuelly.com/forums/f33/dfco-questions-9561.html)

GasSavers_BEEF 07-30-2008 07:47 AM

DFCO questions
 
I just found out (yesterday) that my wife's car has this feature. maybe more cars have it than I know about. her car is pretty far from being fuel efficient.

she drives a honda element with all wheel drive but it does have the 2.4L 4cyl though.

she is getting about 24.5 MPG. I am wondering about how the DFCO works. I have always disregarded any knowledge about the DFCO thing because it never applied to me.

how can she better utilize this function and is it possible for a vehicle like the one described above to achieve 30MPG?

any suggestions would be great. I just recently convinced her to hook up the scangauge in her ride. if nothing else, it is a start.

aalb1 07-30-2008 09:59 AM

Quote:

Originally Posted by BEEF (Post 113136)
I have always disregarded any knowledge about the DFCO thing because it never applied to me.

Your Cavalier doesn't have this function?

I think it was my post from yesterday that was the source of your "Eureka DFCO Moment." The way that I have been using it mainly on approaching red lights. For instance I know the exact spot on the off ramp towards my house to release the throttle at 50mph so I can cruise the rest of the way in third gear to the stop light. Since this off ramp has an uphill curve to it a lot of people end up slowing down at the curve, accelerating after the curve, then braking at the light. Compare that method and gas usage to my DFCO method with ZERO gas usage. Now attempt to do this with every off ramp, traffic light, traffic jam, stop sign, intersection etc. etc. and the MPG figure starts to increase.

No offense to your wife, and no offense to the female hypermilers on this site but what I explained above is way too much hassle for my wife. No matter how much I talk about FE I'd never expect my wife to put any of those techniques into practice. Most FE techniques are way too much hassle for the average male driver too.

theholycow 07-30-2008 10:00 AM

I doubt any car from this century is completely unable to DFCO (unless of course it's been modified). I also doubt any Honda after maybe 1995 entirely lacks DFCO.

It seemed like a really great thing when I first learned about it, but its real world usage is limited. Really all you can do is be aware of it and try to optimize for it while slowing/stopping (by knowing the exact conditions in which it works and trying to stay in those for as long as possible), and also try not to feather the throttle -- either apply some power or get completely off so it can DFCO.

GasSavers_BEEF 07-30-2008 10:35 AM

the diffucult thing (as stated above) is that it is on my wife's car. she is just now starting to understand that if we can lower our fuel costs then we will have money for other things. she isn't willing to do a lot of stuff but the sheer fact that she has started to care may mean that she is changing her mind about all of this.

also I assume that if I were to buy a new honda or toyota that it will have this feature as well? my car doesn't have it but it is a 97 chevy so I can't expect it to have all the cool stuff anyway.

theholycow 07-30-2008 10:58 AM

The wife factor...yeah, that's a tough one. I knew it was a lost cause right from the start and didn't bother. Instead, I mostly just kept it to myself. I occasionally gave her a brief description of a gas saving technique, or talked about it to someone else while she was around, and I drove with some hypermiling practices while she was a passenger but did not say anything unless she asked. She has decided to do a little, and tried P&G which provided a decent FE benefit but isn't compatible with her Isuzu (see my thread titled something like "I've finally found an automatic that doesn't like neutral coasting").

FWIW, my 2002 GMC and my 2008 VW both have it, though it's mostly useless on the GMC due to the delay before it activates (I suspect that a custom tune could change that).

If a 2002 GMC full size V8 pickup has it, and a 2008 VW with awfully short gears/close ratios for boy-racers has it, I would be hard pressed to believe that any new car, Honda, Toyota, GM, Ford, or even Kia would not have DFCO.

Jay2TheRescue 07-30-2008 11:12 AM

Quote:

Originally Posted by theholycow (Post 113179)
The wife factor...yeah, that's a tough one. I knew it was a lost cause right from the start and didn't bother. Instead, I mostly just kept it to myself. I occasionally gave her a brief description of a gas saving technique, or talked about it to someone else while she was around, and I drove with some hypermiling practices while she was a passenger but did not say anything unless she asked. She has decided to do a little, and tried P&G which provided a decent FE benefit but isn't compatible with her Isuzu (see my thread titled something like "I've finally found an automatic that doesn't like neutral coasting").

FWIW, my 2002 GMC and my 2008 VW both have it, though it's mostly useless on the GMC due to the delay before it activates (I suspect that a custom tune could change that).

If a 2002 GMC full size V8 pickup has it, and a 2008 VW with awfully short gears/close ratios for boy-racers has it, I would be hard pressed to believe that any new car, Honda, Toyota, GM, Ford, or even Kia would not have DFCO.

I wonder if the Beast has it? I don't think it does. Its the last year of that body and the 350 V-8. They probably started with model year 1999 trucks. Then again, it might and like you said its virtually useless because of the delay.

theholycow 07-30-2008 11:19 AM

Quote:

Originally Posted by Jay2TheRescue (Post 113181)
I wonder if the Beast has it? I don't think it does. Its the last year of that body and the 350 V-8. They probably started with model year 1999 trucks. Then again, it might and like you said its virtually useless because of the delay.

There's a sure way to find out for yourself. I think you know...you've read enough of my posts. Just click on the DIY fuel rate meter link. ;)

I'd guess that it's pretty unlikely, considering the way my newer generation 2002 model with a much newer engine and computer acts. Then again...
http://www.google.com/search?q=1999+gm+5.7+v8+dfco
http://service.gm.com/gmspo/mode6/pd...t57R_LD_tE.pdf
Considering that GM's own service PDF (hey, cool find!) for the 1999 C/K L31 5.7 says to test the O2 sensor while in DFCO, I guess you've got it.

Jay2TheRescue 07-30-2008 11:29 AM

Quote:

Originally Posted by theholycow (Post 113183)
There's a sure way to find out for yourself. I think you know...you've read enough of my posts. Just click on the DIY fuel rate meter link. ;)

I'd guess that it's pretty unlikely, considering the way my newer generation 2002 model with a much newer engine and computer acts. Then again...
http://www.google.com/search?q=1999+gm+5.7+v8+dfco
http://service.gm.com/gmspo/mode6/pd...t57R_LD_tE.pdf
Considering that GM's own service PDF (hey, cool find!) for the 1999 C/K L31 5.7 says to test the O2 sensor while in DFCO, I guess you've got it.

But mine is a 98 with the 5.7. I've got the SG set to report fuel rate, and I've never seen it go to zero while engine braking, but then since I've gotten the SG I've been shifting into Neutral to gain the biggest instant MPG's possible. How long is the DFCO delay? What are the RPM ranges on your truck? I have a couple of hills I can try to force it into DFCO (if they are long/steep enough)

-Jay

EDIT: I changed the search parameter to 1998 and it appears to have it. I wonder what the conditions are required for it to activate? From your comments it sounds like its only useful for engine braking going down a mountain.

-Jay

theholycow 07-30-2008 11:47 AM

Oops, I don't know why I thought yours was a '99, that would be the new body style...

ScanGauge isn't good at detecting DFCO nor can it measure fuel rate. It reports fuel rate by guessing and calculating. Set one of its readings to show Open/Closed Loop; if you see Open Loop while off the gas pedal you're almost certainly in DFCO.

In my 2002 5.3, it takes 6 to 10 seconds of engine braking above 1500 rpm before it will DFCO. For demonstration purposes, take it up to 70mph and drop to 3rd; that should put you in the 2500-3000 rpm range and should last long enough to assure DFCO even if you're not going downhill.

R.I.D.E. 07-30-2008 11:49 AM

I use DFCO with additional braking by turning on the AC, for free cool air. Saves me having to run AC otherwise, when temps are close to 100 outside. Instead of sitting at the light melting, I use DFCO to delay my arrival and provide a little cool air, just in case I come to complete stop.

regards
gary


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