Using DFCO to increase your MPG - Page 7 - Toyota Yaris Forums

GMKing · 08-31-2009, 04:54 PM

I just bought my toyota yaris this last friday and I love it, but one thing has been bothering me and I think it may be this DFCO

when I coast my vehicle (automatic, btw) without going into neutral it seems to "drag" kind of like engine braking, but when I coast it in nuetral there's no drag. I was wondering is this "drag" the DFCO? and if it saves on fuel then why does it cause the vehicle to slow down at a faster rate than in neutral?

Yaris Hilton · 09-01-2009, 12:22 AM

Yes, it's the DFCO. Yes, it slows down the car faster than coasting in neutral, because the car's momentum is spinning the engine with no power being generated, just drag. It's not meant for increasing gas mileage, but for eliminating exhaust emissions while the car is coasting. If it's coasting down a steep enough hill to overcome the drag, you're saving gas over having the engine still running at idle power. If you're on level ground, you'll save gas whenever you're coasting toward a stop and would be using the brakes sooner without it. But it won't always save gas. Under conditions where it makes you slow more than you want to and you have to give it more gas to make it up, you may lose a bit.

GMKing · 09-01-2009, 03:34 PM

exactly the issue i've been having. the fact that it slows down quicker as I'm trying to coast really aggravates me, screw emissions, I'm trying to get somewhere, guess I'm just gonna have to get into the habbit of putting in neutral

Yaris Hilton · 09-01-2009, 05:21 PM

I've gotten used to the DFCO and pay little attention to it. But at the moment I'm travelling with the family in my old minivan that doesn't have DFCO, and it's startling how slowly it decelerates on flat ground with the engine idling! I have to use the brakes a lot more.

09Yarisguy · 09-02-2009, 02:49 AM

I appreciate this thread and forum...I had no idea my new car had this system so I've been throwing it in idle on long downhills or rolling to a stop and being proud of the 38.5 MPG average I've gotten so far. I will try this with my next tank for comparison and let you know exactly what this does for me.

Just FYI though, there are a few places I'll still be coasting since there's a couple of half mile lengths on the highway where I can roll without losing any momentum. I figure I save a bit on gas for idling instead of gassing and I get a nearly free mile out of each trip to work.

BailOut · 09-02-2009, 09:42 AM

It sounds like you're off to a great start, 09Yarisguy.

127.0.0.1 · 10-20-2009, 09:56 AM

2010 yaris 5dr HB,

I find that scangauge cutoff set to 16 most accurately represents DFCO and 21 did not.

21 reported 9999 when I was not DFCO, merely foot off gas at 60mph which is not DFCO...there is still some fuel running to keep my decel rate from dropping too much. 16 now it never misreports.

I watched TPS. TPS lowest number is 15, but DFCO still will not always occur at TPS 15. But DFCO cannot occur anywhere
16 or above, so cutoff at 16 is perfect. when i drop to 15, scangauge reports some high mileage 180 or so, but won't
flash me the 9999 until I feel (with me arse dyno) the actual DFCO condition. so...I think...at least for my piglet, cutoff 16 is accurate.

Yaris Hilton · 10-20-2009, 10:00 AM

Foot off gas at any speed with the torque converter locked up and engine spinning over about 1000 RPM puts mine into DFCO. I can feel the sudden small increase in drag after about 1/2 second.

jtcoop · 10-22-2009, 08:59 PM

OK everybody I bought a Kiwi MPG and now I am having difficulty seeing or believing the DFCO theory. Traveling at say 40 mph going down hill, I let off the gas and the IMPG reads 165 MPG. If I push the clutch in the reading jumps to 180 or higher. The more speed I gain going down a hill with the clutch in the higher the IMPG reads. I have even tried tapping the brakes. Am I missing something? I will try and see what the LOD reading are tonight. I know at idle the LOD reads 16. I am not sure what it reads when I take my foot off the accelerator at 40 mph versus foot just touching the accelerator.
Regardless I am looking forward to my further education on the subject.

Yaris Hilton · 10-22-2009, 11:50 PM

DFCO's not a theory. If your Scangauge isn't showing it, it's improperly set.

jtcoop · 10-23-2009, 02:34 AM

For those who have a Scanguage, ( I do not ), when it is displaying Instant Gas Mileage, you take your foot off the accelerator, you get a large increase in the MPG being displayed. If you depress the clutch, do the numbers go up or down. With my experience it is going up. I, like most am trying to get the most bang for the buck. It makes sense to me that if the numbers go up with the clutch depressed, then I am getting more bang.
Yaris H, could something be wrong with the car? I am trying to find someone in my area that has a Scanguage to compare the IMPG.

Yaris Hilton · 10-23-2009, 07:17 AM

I doubt anything's wrong with the car. DFCO's supposed to kick in after about 500-700 milliseconds. Are you waiting for it? You don't need a Scangauge to feel the sudden drag, it slows the car down.

127.0.0.1 · 10-23-2009, 08:55 AM

DFCO kicks in when

there is something in the transmisson keeping the engine spinning so the engine
doesn't actually stop turning

and when

the decel rate DFCO will make won't spill your coffee. it is programmed to kick in
but not make it buck. hence...in an automatic, it won't always kick in when foot
is off gas.

Yaris Hilton · 10-23-2009, 10:25 AM

Quote:

Originally Posted by 127.0.0.1

the decel rate DFCO will make won't spill your coffee. it is programmed to kick in
but not make it buck. hence...in an automatic, it won't always kick in when foot
is off gas.

It never makes it buck. But you can feel a small jerk when the fuel cuts out. It's definitely slowing down. The automatic usually has the torque converter locked when you're cruising around at light throttle, even poking around town at 25 MPH. Watch the tach. When the torque converter's unlocked, the engine speed will swing up and down with more or less pressure on the throttle. With it locked, the RPMs stay in strict lockstep with the speed on the speedometer.

Older automatic Yarises before mid-2007 model year may not have DFCO in Drive.

jtcoop · 10-24-2009, 01:25 AM

When the RPMs reach 1100 and I actually feel the fuel cut back on, if I just let the car continue to coast. So I am pretty confident DFCO is working. I did notice today that the Load was reading 18 at one point on a long down hill run on the expressway. When I depress the clutch it went to 16. I thought I read somewhere in this post that Load had to be at 15 or 16 before DFCO would start. Right or wrong?
Everybody I again just want to say "Thank you" for your patience!

My bad....just reread very first post! Bail Out answered the Load question

Yaris Hilton · 10-24-2009, 08:19 AM

Mine doesn't seem to kick in DFCO below about 1100 RPM, but also doesn't kick it back to idle power till it drops below about 800 RPM on the tach once DFCO's on. (I think at the same time it unlocks the torque converter.)

jjonrofl · 12-16-2009, 03:12 PM

I've read most of these and think I finally know what it is- is it when I go down a steep hill going about 40-45, and when I touch the brakes, it buzzes and begins to brake steadily down the hill? If so, should I try to make this happen?

BailOut · 12-16-2009, 03:19 PM

Quote:

Originally Posted by jjonrofl

I've read most of these and think I finally know what it is- is it when I go down a steep hill going about 40-45, and when I touch the brakes, it buzzes and begins to brake steadily down the hill? If so, should I try to make this happen?

You don't have to touch the brakes to make it kick in. It will happen by itself shortly after you take your foot off of the gas pedal.

09-02-2009, 09:42 AM	#114
BailOut Steals terrorist's lunch View User's Garage Drives: 2007 Yaris Liftback Join Date: Mar 2007 Location: Reno, Nevada, USA Posts: 1,299	It sounds like you're off to a great start, 09Yarisguy. __________________ - Brian Share the Road I often carry 2 carpool passengers and mountain bikes or snowboards/skis over a 4,500 foot elevation difference. Click the graphic above to see my detailed mileage logs.

10-24-2009, 01:25 AM	#123
jtcoop Drives: 07 Yaris, LB, MT, Bayou Blue Join Date: Sep 2009 Location: Clemmons, NC Posts: 14	When the RPMs reach 1100 and I actually feel the fuel cut back on, if I just let the car continue to coast. So I am pretty confident DFCO is working. I did notice today that the Load was reading 18 at one point on a long down hill run on the expressway. When I depress the clutch it went to 16. I thought I read somewhere in this post that Load had to be at 15 or 16 before DFCO would start. Right or wrong? Everybody I again just want to say "Thank you" for your patience! My bad....just reread very first post! Bail Out answered the Load question Last edited by jtcoop; 10-24-2009 at 01:29 AM. Reason: Old timers kickin in

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08-31-2009, 04:54 PM	#109
GMKing Drives: 2007 toyota Yaris sedan Join Date: Aug 2009 Location: Portsmouth VA Posts: 10	I just bought my toyota yaris this last friday and I love it, but one thing has been bothering me and I think it may be this DFCO when I coast my vehicle (automatic, btw) without going into neutral it seems to "drag" kind of like engine braking, but when I coast it in nuetral there's no drag. I was wondering is this "drag" the DFCO? and if it saves on fuel then why does it cause the vehicle to slow down at a faster rate than in neutral?

09-01-2009, 12:22 AM	#110
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	Yes, it's the DFCO. Yes, it slows down the car faster than coasting in neutral, because the car's momentum is spinning the engine with no power being generated, just drag. It's not meant for increasing gas mileage, but for eliminating exhaust emissions while the car is coasting. If it's coasting down a steep enough hill to overcome the drag, you're saving gas over having the engine still running at idle power. If you're on level ground, you'll save gas whenever you're coasting toward a stop and would be using the brakes sooner without it. But it won't always save gas. Under conditions where it makes you slow more than you want to and you have to give it more gas to make it up, you may lose a bit.

09-01-2009, 03:34 PM	#111
GMKing Drives: 2007 toyota Yaris sedan Join Date: Aug 2009 Location: Portsmouth VA Posts: 10	exactly the issue i've been having. the fact that it slows down quicker as I'm trying to coast really aggravates me, screw emissions, I'm trying to get somewhere, guess I'm just gonna have to get into the habbit of putting in neutral

09-01-2009, 05:21 PM	#112
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	I've gotten used to the DFCO and pay little attention to it. But at the moment I'm travelling with the family in my old minivan that doesn't have DFCO, and it's startling how slowly it decelerates on flat ground with the engine idling! I have to use the brakes a lot more.

09-02-2009, 02:49 AM	#113
09Yarisguy I've made a post! Drives: Base 4 door sedan Join Date: Sep 2009 Location: Austin, TX Posts: 1	I appreciate this thread and forum...I had no idea my new car had this system so I've been throwing it in idle on long downhills or rolling to a stop and being proud of the 38.5 MPG average I've gotten so far. I will try this with my next tank for comparison and let you know exactly what this does for me. Just FYI though, there are a few places I'll still be coasting since there's a couple of half mile lengths on the highway where I can roll without losing any momentum. I figure I save a bit on gas for idling instead of gassing and I get a nearly free mile out of each trip to work.

10-20-2009, 09:56 AM	#115
127.0.0.1 Banned Drives: '10 Yaris5drHB+99 4runner LTD Join Date: Sep 2009 Location: NE Posts: 672	2010 yaris 5dr HB, I find that scangauge cutoff set to 16 most accurately represents DFCO and 21 did not. 21 reported 9999 when I was not DFCO, merely foot off gas at 60mph which is not DFCO...there is still some fuel running to keep my decel rate from dropping too much. 16 now it never misreports. I watched TPS. TPS lowest number is 15, but DFCO still will not always occur at TPS 15. But DFCO cannot occur anywhere 16 or above, so cutoff at 16 is perfect. when i drop to 15, scangauge reports some high mileage 180 or so, but won't flash me the 9999 until I feel (with me arse dyno) the actual DFCO condition. so...I think...at least for my piglet, cutoff 16 is accurate.

10-20-2009, 10:00 AM	#116
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	Foot off gas at any speed with the torque converter locked up and engine spinning over about 1000 RPM puts mine into DFCO. I can feel the sudden small increase in drag after about 1/2 second.

10-22-2009, 08:59 PM	#117
jtcoop Drives: 07 Yaris, LB, MT, Bayou Blue Join Date: Sep 2009 Location: Clemmons, NC Posts: 14	OK everybody I bought a Kiwi MPG and now I am having difficulty seeing or believing the DFCO theory. Traveling at say 40 mph going down hill, I let off the gas and the IMPG reads 165 MPG. If I push the clutch in the reading jumps to 180 or higher. The more speed I gain going down a hill with the clutch in the higher the IMPG reads. I have even tried tapping the brakes. Am I missing something? I will try and see what the LOD reading are tonight. I know at idle the LOD reads 16. I am not sure what it reads when I take my foot off the accelerator at 40 mph versus foot just touching the accelerator. Regardless I am looking forward to my further education on the subject.

10-22-2009, 11:50 PM	#118
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	DFCO's not a theory. If your Scangauge isn't showing it, it's improperly set.

10-23-2009, 02:34 AM	#119
jtcoop Drives: 07 Yaris, LB, MT, Bayou Blue Join Date: Sep 2009 Location: Clemmons, NC Posts: 14	For those who have a Scanguage, ( I do not ), when it is displaying Instant Gas Mileage, you take your foot off the accelerator, you get a large increase in the MPG being displayed. If you depress the clutch, do the numbers go up or down. With my experience it is going up. I, like most am trying to get the most bang for the buck. It makes sense to me that if the numbers go up with the clutch depressed, then I am getting more bang. Yaris H, could something be wrong with the car? I am trying to find someone in my area that has a Scanguage to compare the IMPG.

10-23-2009, 07:17 AM	#120
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	I doubt anything's wrong with the car. DFCO's supposed to kick in after about 500-700 milliseconds. Are you waiting for it? You don't need a Scangauge to feel the sudden drag, it slows the car down.

10-23-2009, 08:55 AM	#121
127.0.0.1 Banned Drives: '10 Yaris5drHB+99 4runner LTD Join Date: Sep 2009 Location: NE Posts: 672	DFCO kicks in when there is something in the transmisson keeping the engine spinning so the engine doesn't actually stop turning and when the decel rate DFCO will make won't spill your coffee. it is programmed to kick in but not make it buck. hence...in an automatic, it won't always kick in when foot is off gas.

10-24-2009, 08:19 AM	#124
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	Mine doesn't seem to kick in DFCO below about 1100 RPM, but also doesn't kick it back to idle power till it drops below about 800 RPM on the tach once DFCO's on. (I think at the same time it unlocks the torque converter.)

12-16-2009, 03:12 PM	#125
jjonrofl Drives: 2009 Yaris LB Join Date: Dec 2009 Location: Maryland, USA Posts: 37	I've read most of these and think I finally know what it is- is it when I go down a steep hill going about 40-45, and when I touch the brakes, it buzzes and begins to brake steadily down the hill? If so, should I try to make this happen?