Any Big Savings In Coasting In Neutral With Engine On?
 

Is there any big saving in just throwing the car into N but not turning engine off?
For instance when approaching a red light from a block away i will throw into N and cruise to a slow stop.Or if im going down a steep hill.
I am not crazy about turning engine off with an automatic.

Hello,

It is hard to turn off the engine in any car -- steering and braking are very difficult w/o the engine running. So, yes, shifting to neutral saves fuel.

I coast as much as possible and where traffic allows. This alone has saved me fuel.

I coast as much as I possibly can, and it definitely gets me a couple of mpg.

Coasting in gear will probably save fuel. I lost FE when coasting in neutral (automatic trans) because apparently there is a fuel cutoff in my vehicle. It actually burns fuel when in N instead of not burning when coasting in D.

Also, I don't know if going into neutral is too good for your tranny, I made a thread about that and it had mixed answers. http://ecomodder.com/forum/showthrea...anny-1153.html

I think it depends a lot on the car. My Malibu seems to shift back into gear fine even at highway speeds. Also, idle is higher when in gear, ie, in park or neutral the TPS will be 7 clicks open, in gear it will usually stay 10-13 clicks open. Playing around the other day waiting in line at the border crossing I got
Idle, in gear, AC on - 0.51 gph
Idle, in gear, AC off - 0.43 gph
Idle, in neutral, AC on - 0.41 gph
Idle, in neutral, AC off - 0.29 gph

Looking at that tells me there could be some significant fuel savings coasting in neutral, especially with turning off AC.

But like everyone says, every car is different.

I hear yah, I've got a HCH1 and whenever I put it in neutral (it doesn't turn off like the prius does unless you have the break engaged) it maxes out on the millage where when I'm just coasting sometimes it doesn't. It will save gas if you do it at a stop light, and it would be easier on the car as well, right?

Not really "any" car, manual steering cars don't have any steering issues with the engine off and the reserve brake vacuum is managable, heck I can lock the tires up even when the vacuum is gone. But I also have a parking brake and engine braking (stick shift) if necessary. It really just a matter of practice, in a safe location preferrably.

But even in our power steering saturn, the steering effort isn't unbearable as long as the car is rolling. My wife manages the corners just fine. Though I would like to eventually swap in a manual rack just to save a bit more gas by not constantly running the power steering pump.

It really depends on the driver and car.

In my automatic Neon I do alot of coasting with the engine on, on the highway. At 100km/h it coasts in neutral at about 1.7L/100km where if I'm in gear just giving enough gas to counteract engine braking the scangauge reads about 3.5 or 4L/100km. In town I don't bother going into neutral unless I can sneak a glide in. My car doesn't read any different idling in or out of gear.
Going back into gear at 50mph is a bit of a trick, I find if I try to rev match by holding the throttle open the tranny will think about going into second gear for a second, but if I just blip the gas it goes into 3rd(highest gear) and I tickle the gas some more and it locks the converter for the next pulse, shoot up to 100km/h and repeat.
On my last trip home I got 5.4L/100km in an auto Neon so I must've done something right!
Ian

Not scientific by any means, but according to SGII I get better fuel economy coasting in gear? Possibly a false positive.

http://youtube.com/watch?v=P_en3k_D0c4

I made this video yesterday on the same topic for another forum.

thanks for the video, that kind of think is very helpful

I bet my car slows 2-3X faster in gear. That can't be more efficient.

dsq -

I would never EOC with an automatic unless I knew everything about it's design. Coasting in Neutral is easy for me because I have a manual tranny. The RPMs drop much closer to idle, and the Scangauge *shows* me how much MPG I am gaining. Coasting in neutral is a big part of Pulse and Glide (the mild kind with engine on). I don't know what the benefit will be in an auto because they're designs are less "predictable" in terms of their design/behavior.

CarloSW2

Arminius -

Correct, but (big) if you have automatic fuel-cutoff while "coasting in gear", then it can be strategic. If you see a stop up ahead, coast-in-gear to engine-brake and get fuel-cutoff for free.

CarloSW2

thebrad -

Yeah, I think you have fuel-cutoff going for you. The best way to confirm would be to splice into the fuel injector pulse wires like they are doing for the MPGuino, but when I see that 9999 (divide by zero => largest number that can be displayed), I think fuel-cutoff too.

Another (indirect) way would be to get an A/F gauge. If you see the gauge go super lean when the SG shows 9999, then it would imply that you have fuel cutoff.

I wonder if you can see your 02 sensor output with an X-Gauge function. It's a 1996 Honda, so it *might* be available to you. Hard to tell. I don't know because I don't have a 1996 Civic.

CarloSW2

With my GMC 2.2l fuel injected coasting in neutral uses fuel whereas coasting in gear turns the injectors off and uses no fuel. This is true if the coasting speed (engine RPM) is fast enough.

I live in a very hilly area. going down many of the hills requires braking, engine braking or otherwise. If I were to put it in N going down the hills it will use fuel at the rate of engine idling, and I have to apply the brakes to slow down. But if I leave it in gear it uses no fuel going down the hill and also serves to slow the vehicle.

In my vehicle coasting in N only helps FE if the engine is OFF, and even then it only makes sense if I do not want the engine brake affect, which I often need where I drive.

Willing to try it "for science" if you can give me the XGauge coding. :thumbup:

This is something i had to try.


as far as my rig, (auto transmission) coasting in N was not beneficial

test 1, coast to a stoplight in gear
test 2, coast to a stoplight in N
test 3, coast in N, engine on, at 55 on the highway

in test 1, engine dropped to around 400 rpms
in test 2, engine stayed at around 1200 rpms
in test 3, transmission got "confused". the trans started hunting gears with a lot of slipping of the torque converter

so basically i learned to just get my foot completely off the gas as much as possible with the engine still running. when i get to a stoplight i know is going to be long, i put it in N after i come to a complete stop, then turn off the engine.

i'm curious to see how this effects my mpg, hopefully it will help offset the added weight of a trailer, wood, and construction equipment i've been hauling on part of this tank.

Hi all,
I have an '03 Taurus 3 liter automatic. I have done the coasting both in gear and in neutral. What I see on my SG is about a 30% mpg gain if I coast in neutral. for example if I show 60mpg in drive, then shift to neutral, the there is a corresponding increase to about 80mpg. I have found this to generally be the case. I do not glide at over 40 mph although so far I haven't found any problems shifting back and forth at speeds below that. I do have about a two second time delay for the tranny to return to the proper pressure for whatever the current speed might be before I re-engage the throttle. Otherwise there is lag in the acceleration and then a sudden jerk when the tranny engages.
At stops, there is almost always a 30% loss in economy if left in drive rather than neutral. Ex: idles at .29gph in idle, .40gph in drive. So I have to conclude that yes there is some savings by just slipping into neutral.
JJ

I drive down several large hills on a daily basis and just recently i decided to try coasting in neutral. Its fairly easy as I drive a standard so when it comes time to go back into gear i just rev the engine to where the rpm should be and shift back into gear. I got a 4mpg gain which is a 20% increase for my vehicle. Stop signs and such i do the same thing mainly because i have to otherwise i'll stall but 900rpm should be better then 3000

thebrad -

I did some googling but no luck. 1996 Civic codes are probably harder to find. I think this is a Civic Tuner Forum question.

CarloSW2

Without a gauge to show actual FE, I can only guess, but coasting in gear shortens the distance I can coast. When stopped, all I can go by is the tach: in gear is usually around 800 rpm vs 1000 rpm in neutral.

It also seems to depend on the speed sometimes; if I'm doing <45 and I coast in gear, the tach drops ~500 rpm but > 45 it doesn't drop noticeably (maybe 100?) and there's the engine drag.

Until I get the time to put a 'Guino together (I'm not paying for a SG), I'll just stick with my "neutral coast, stop in gear with engine on" policy.

if i need engine braking, of course, coasting in gear is the best, with or without injector cutoff as needed.

if i don't need engine braking, of course, coasting in neutral is the best, with engine off or idling as needed.

any vehicle getting better mileage coasting in gear, would have to have some kind of over-running clutch system, and a very smart ECU, that idled the engine at the same time.

the only one i have driven that did this was an Audi turbo-diesel with the transmission in E.

It definitely has advantages. Heading down a small hill that goes slightly up hill you can coast down, gain speed, level out at top and then go back into gear (Or just slowly let out the clutch and match rpms).

I've started coasting a LOT more as I come to stops, cover large distances when approaching traffic and in situations where it makes no sense to be engine braking and what have you.

This has saved me some good gas mileage :) So to answer the originating question:

YES :)

kinda like a hybrid

Don't do EOC in an automatic-equipped car. Coasting in neutral should be fine; I've been doing it for a long time in the Forester at speeds up to 75mph (we get some steep hills here in the Appalachians) and suffered no ill effects, but the front end of the tranny has to be turning to keep the rest of the tranny lubed. You can coast with the engine on, and turn the engine off at lights, but when rolling, the engine should be on.

And yeah, it's worth it. A Forester is heavy and shaped a bit like a LEGO block, but I've dragged its mpg up from an average of 25 to about 29.1.