Using DFCO to increase your MPG

[Sodium Duck]

*thinking - thinking - thinking* Oh snap, you're wrong!

On initial thought, you're scenarios make sense. But -- you have to look at the big picture. As I said before, it depends on the situation which driving technique/tool you should use. There is no one perfect, end all - be all, thing to do to save gas. It is a mix of things that you do and when you do them. Now, you tell me which one of my scenarios is more efficient.

Going down a small hill, that levels out at the bottom for 400 yards, until you get to a stop sign.

You COULD use DFCO, use no gas at all on the small hill portion, then be forced to use gas at the bottom because you would have no momentum left.

OR

You COULD shift into neutral and simply coast to the stop sign - not touching the gas once.

OR

You COULD build up some speed on the other side of the hill, and turn your car completely off at the crest (granted you have a manual).

OR

You COULD do whatever to get down the hill, then use hang time to get to the stop sign.

OR

You COULD go crazy, remove your spare tire, rear seat, stereo, interior plastic, go on a diet and lose soem weight, etc. Drop a couple hundred pounds of weight from the vehicle and just drive over the hill normally.

I don't feel like digging out the numbers, because, as I said before, this has been discussed many, many times here before. DFCO is the most fuel efficient thing to do when you use it in conjunction with ALL driving techniques/tools. There are many things you can do to get better MPG, but DFCO is not always the best. You have to consider the bigger picture!

[Sodium Duck]

Originally Posted by voodoo22

Like Sodium Duck says, it's a combination of techniques based on your situation. In situations where you don't want to slow down, but the decline is not steep enough to allow you to use DFCO without losing speed. That's when you want to use N.

You are also wrong about coasting in N in an auto. Most newer autos have no problems and incur no damage from doing this. You don't need to rev match or anything.

It really doesn't matter how efficient a maneuver is with a MT when you're driving an AT. Most AT's cannot ICE off coast without incurring damage, but some can. For the masses who can't N-ICE on coasting is their best choice when DFCO isn't suitable.

*clapping* Thank you!

And umm, what's ICE stand for? All I can think of is "in car entertainment."

[BailOut]

ICE = Internal Combustion Engine

[songa]

Originally Posted by Sodium Duck

*thinking - thinking - thinking* Oh snap, you're wrong!

On initial thought, you're scenarios make sense. But -- you have to look at the big picture. As I said before, it depends on the situation which driving technique/tool you should use. There is no one perfect, end all - be all, thing to do to save gas. It is a mix of things that you do and when you do them. Now, you tell me which one of my scenarios is more efficient.

Going down a small hill, that levels out at the bottom for 400 yards, until you get to a stop sign.

You COULD use DFCO, use no gas at all on the small hill portion, then be forced to use gas at the bottom because you would have no momentum left.

OR

You COULD shift into neutral and simply coast to the stop sign - not touching the gas once.

OR

You COULD build up some speed on the other side of the hill, and turn your car completely off at the crest (granted you have a manual).

OR

You COULD do whatever to get down the hill, then use hang time to get to the stop sign.

OR

You COULD go crazy, remove your spare tire, rear seat, stereo, interior plastic, go on a diet and lose soem weight, etc. Drop a couple hundred pounds of weight from the vehicle and just drive over the hill normally.

I don't feel like digging out the numbers, because, as I said before, this has been discussed many, many times here before. DFCO is the most fuel efficient thing to do when you use it in conjunction with ALL driving techniques/tools. There are many things you can do to get better MPG, but DFCO is not always the best. You have to consider the bigger picture!

thanks duck, thats the clarification i needed. i was just under the impression that DFCO WAS in fact the way to go whenever possible....however i was in a similar scenario as the 2nd one you mentioned and started thinking that N coasting might actually be more beneficial as i didnt feel comfortable with the engine braking limiting my momentum on a hill. and YES, like bullet120 said, DFCO uses no gas at all so is technically more efficient, but in certain situations, you may encounter a trade off where you can benefit form the extra speed you can obtain from N coasting, even for a lil gas consumption. arite thanks guys!

[silver_echo]

found out last night that my 01 echo does have DFCO! sweetness!

[Slick]

Alright, I read all six pages and noone stated the answer to my soon to be question. It has been stated that the A/T will not enter DFCO in D. Then it was stated that it might inter DFCO in D, or at least enter "grade logic". It was discussed that shifting between N and D or 3 and D may or may not be harmful to an A/T.

Soooo, in order to get best results on a non-grade road, should I downshift 3,2,1 (in order to keep the RPMs up) in order to stay in DFCO while coming to a stop? If so, this isn't bad for the transmission? Or is it that as long as i'm not winding the tranny up to 4 or 5k on a downshift it will be fine?

Would ya'll recomend just shifting from D to 3 and just riding that for as long as possible?

Thanks in advance for any help or advice.

[MadMax]

Slick

I've been led to believe that the AT will cause the DFCO to kick it but not as quickly as a manual would. However, I downshift to '3' and even down to '2' to maximize the DFCO savings. It seems to help...and it should not cause any problems with the transmission as long as you aren't downshifting to '2' at 70 MPH...

Cheers! M2

[Maxh91]

Originally Posted by MadMax

Slick

I've been led to believe that the AT will cause the DFCO to kick it but not as quickly as a manual would. However, I downshift to '3' and even down to '2' to maximize the DFCO savings. It seems to help...and it should not cause any problems with the transmission as long as you aren't downshifting to '2' at 70 MPH...

Cheers! M2

I'm not an Transmission pro (AT) but how much high the RPM can be in 3th when downshift to 2? I only downshift at 1300 to be sure. I don't want to destroy my AT if i downshift to early! I don't really know how much the AT can rev safely when engine braking.

[MadMax]

I wouldn't pop down to '2' above 40 MPH, that's about my upper limit...your car will let you know if you downshift too early!

Cheers! M2

[Slick]

It has been my experience that the best way to tell when to downshift an automatic (don't flame me hypermilers) is to accelerate slowly starting in 1 and listening to the engine. When its starts to whine medium-loud then you know you should move it into 2. Repeat all the way to drive. After this, you should be able to guesstimate when its safe to downshift. eg. Shift from D to 3 anywhere under 50. 3 to 2 anywhere under 25. 2 to 1 under 15. This example is probably not at accurate shifting speeds, its only an example.

[Darb]

Originally Posted by BailOut

Now tun off your ignition (This is where you may lose your PS/PB, so be wary!) and watch for any harsher deceleration or change in the pitch of the engine for a few seconds.

Whoa whoa, question. Doesn't the AT require you to be in park (P) in order to restart the engine? Or are you just shifting down to 3 and L? *confused*

[BailOut]

Originally Posted by Darb

Whoa whoa, question. Doesn't the AT require you to be in park (P) in order to restart the engine?

Hello Darb,

No, you can start it from N(eutral) as well. However, if you would like to do it from P(ark) you still have your power brakes after the engine is off for at least 4 touches.

[Marthos]

Lets make this simple.

DFCO is for slowing and/or stopping the car,

If you need to stop at the bottom of a hill, or you want to go slower down a hill, DFCO is for you.

Start down the hill, Auto Trans people may need to tap breaks or even downshift into 3, Manual people just let off the fuel pedal.

The engine will start to try to slow the car, at this point your not using ANY GAS (DFCO).

When at or near the bottom apply brakes, when stopped put trans back into D (which is really OD). If you were just slowing the car some, just pop it back to D and hit the go pedal!

You saved gas.


If you were to bump the car into neutral, all the stopping would be on your brakes and the engine would Idle (use some gas) all the way down.

If you need to coast after the bottom of said hill, DFCO is not for you! Coasting on flat ground requires forward momentum, DFCO Scrubs forward Momentum.

If DFCO slows the car to much and you find yourself back on the Go Pedal before the bottom, you are not saving gas.


DFCO stops your fuel injectors from injecting fuel into the cylinders.

[R2D2]

Originally Posted by Marthos

Lets make this simple.

DFCO is for slowing and/or stopping the car,

If you need to stop at the bottom of a hill, or you want to go slower down a hill, DFCO is for you.

Start down the hill, Auto Trans people may need to tap breaks or even downshift into 3, Manual people just let off the fuel pedal.

The engine will start to try to slow the car, at this point your not using ANY GAS (DFCO).

When at or near the bottom apply brakes, when stopped put trans back into D (which is really OD). If you were just slowing the car some, just pop it back to D and hit the go pedal!

You saved gas.


If you were to bump the car into neutral, all the stopping would be on your brakes and the engine would Idle (use some gas) all the way down.

If you need to coast after the bottom of said hill, DFCO is not for you! Coasting on flat ground requires forward momentum, DFCO Scrubs forward Momentum.

If DFCO slows the car to much and you find yourself back on the Go Pedal before the bottom, you are not saving gas.


DFCO stops your fuel injectors from injecting fuel into the cylinders.

Exactly what I have found. If I don't need to slow on the hill or at the bottom I hold just enough pressure on the accelerator to prevent DFCO to gain momentum for the flat or the next uphill if safe to do so.

One of my favorite features about the Yaris AT is it is very user friendly in regards to engine braking. Down shifting/upshifting are very easy and effective due to DFCO and the way the shifter is set up.

R2

[Yaris Hilton]

The AT downshifts to hold back the coasting car if you touch the brake. Touch the gas and it upshifts to coast freely.

[Marthos]

Also, the tranny will not down shift till rpms are safe.

I have tried it on a 1/4 mile, big downhill grade leaving my home lots of times, with a stop sign at the bottom.

i pop it into 3rd going 40, and it downshifts right away and revs ups a tiny bit, when i pop it into 2nd it almost always downshifts right away (2nd goes past 50mph if ya floor it from a stop) rpms go up, sounds kinda cool, then when im at around 25 i pop it to 1st and have to hit the brakes for it to downshift. I think it shifts down when im around 18 to 20 mph.

I dont have a tach, but I am sure it never revs past 5k after it downshifts, I think there is some kinda over-rev saftey lock out possibly?

The whole process seems very nonharmful to me, and i know im saving a little gas and a lot of brakes.

[Marthos]

Tested this today while cold light was on and when popping into first at 25 mph it went right to 1st gear, still dont think it reved much maybe 4k.

Edit = I guess i should mention, this is a steep hill, im on the brakes pretty good when I did shift it to 1st, revs droped fast, I have no tach and am guessing at the rpms.

Edit = Tried again cold light on, into 1st at 30 and it shifted right away, the trans acts totally different when the cold light is on, wonder if this means the shift points could be remapped?

[Marthos]

Guess I can quit testing, found this in owners manual.

Pg 126 (c) using engine braking

"The transmision will downshift to second gear when the vehicle speed drops down to or lower than 53 mph."

First gear is 26 mph.