Coasting in neutral

antodeco

Hey all,
Just wondering if coasting in neutral does any damage to the engine or components?

Rovi

antodeco wrote: »

Hey all,
Just wondering if coasting in neutral does any damage to the engine or components?

Mechanically, I wouldn't think so; be very careful doing it though, the vehicle will 'drive' and handle very differently to normal.

RobAMerc

not a good idea - you loose engine braking.

Guy:Incognito

Did they not work out a few years ago on top gear that you us emore petrol coastig in neiutral than clowign down in gear?

Captain Slow IRL

Engine is more efficient if in gear while coasting, the momentum will keep the engine running. If you have it in neutral, it requires fuel to keep ticking over.

When I was getting driving lessons, the instructor said, for safety reasons, you shouldn't coast in neutral - something to do with what robamerc said!

E92

Never coast in neutral, bar for the car, fuel consumption, and bad for stopping in a hurry! Top Gear said that coasting in gear was using such a small amount of fuel it was effectively nothing.

anthony4335

I do it all the time. Used to do it as a game on the way home from work when I was bored, and see how much better the MPG would get , and on a 25 mile journey it would increase by 1MPG on one hill. I don't think it is bad , but you would certainly fail you driving test if you were to do it.

fletch

I noticed that my fuel consumption was adversely affected while coasting so have stopped doing it completely.
Also as once happened before on my old car, I knocked it out of gear at about 30mph and the engine revs dropped, causing the car to stall with the obvious effects on brakes and steering :eek:

stratos

You can save ton of petrol by coasting, especially if you drive carefully and lift off and coast rather than accelerate and brake.
There is no harm to the engine. Racing drivers use this technique all the time to conserve fuel and brakes over long races.
Using engine braking causes wear to the engine, using the brakes causes wear to the brakes. I know which one I would rather wear.
I drive a car with a large engine and if I can bothered to drive well ahead of myself coast and use the brakes as little as possible I save a ton of petrol. It means leaving a gap between you and the car in front.
The same technique has saved me from a few rear end shunts too.
A famous racing driver once said "If your brakes have completly failed and your running out of fuel after 30 miles, thats ok in a 29.5 mile race"

Terrontress

Someone wrote into the Sunday Times In Gear about this recently and was told not to think about the economics as it is dangerous, illegal and not very bright at all.

So stop it.

E92

Coasting with the car in gear i.e. leaving it in gear but taking your foot of the accelerator is fine, and is a great fuel saver, what's not fine is putting the car into neutral and then coasting.

crosstownk

If you coast in neutral, you are effectively idling the engine, which consumes little fuel. However, if you lift your foot off the throttle and leave the car in gear, the engine goes into 'overrun'. In most modern engines, the ECU recognises overrun and shuts down the injectors resulting in zero l/100km.

Even an old MkI VW Golf that I used to drive had an overrun switch on it's Solex PIC-T carburettor

Masada

coasting in neutral will result in the gearbox turning quicker that its supposed to as the wheels are turning it, while the engine will be at idle (beteen 600-900rpm on average car) and that can give problems with selecting a gear and cause damage to the gearbox in the longterm.
Its not an intellegent thing to do as others have said.,

stratos

I have to admit coasting in neutral doesn't feel right, however in traffic I can't see the problem.
My car is an automatic so it doesn't come into the equation. As the lubricant pump in the autobox needs engine power when moving
I was as surprised as anyone to see neutral gear road coasting being advocated by a famous racing driver ( I forget who it was ). But I tried it on my wifes car and the results are amazing.
But in reality its more about thinking ahead driving, leaving a good gap and anticipating way ahead I think are key.

I was on here before about not using your brakes, I think people thought i meant like fast driving. The reverse is quite the case hanging back drive slowly, leave a good gap. Sure people will sometimes take the gap just drop back again.

As a young man ages ago i understand the need to power into a corner dab the brakes drop a gear, let the engine roar and accelerate out. Thats a different style of driving (and I love it too).

Del2005

stratos wrote: »

You can save ton of petrol by coasting, especially if you drive carefully and lift off and coast rather than accelerate and brake.
There is no harm to the engine. Racing drivers use this technique all the time to conserve fuel and brakes over long races.
Using engine braking causes wear to the engine, using the brakes causes wear to the brakes. I know which one I would rather wear.
I drive a car with a large engine and if I can bothered to drive well ahead of myself coast and use the brakes as little as possible I save a ton of petrol. It means leaving a gap between you and the car in front.
The same technique has saved me from a few rear end shunts too.
A famous racing driver once said "If your brakes have completly failed and your running out of fuel after 30 miles, thats ok in a 29.5 mile race"

So you'd rather risk damage to an engine to save on a consumable Also if you are driving with the correct gap you wouldn't be in danger of shunting the car in front of you.
Or are you coasting in gear and reading the road, as the OP is asking about coasting in neutral?

antodeco

Thanks for the replies. I know its not the smartest thing, but habit has gotten the better of me.
I never do it at the last minute. It would be when approaching from a distance. Plus, I would be breaking at the same time, so I can judge the stopping distance.
What I have noticed though, is sometimes Im dropping from 3rd/4th gear down. Admittingly again, not very clever, but driving for a few hours has a tendency to make me do the 'easier option' of coasting.
Again, I never do this close up. Most of the time its when Im the first car approaching a red light.

@ terrontress, where did you see that it was illegal?

kdevitt

The manual from BMW for the E30 instructed you to coast as often as posisble to help fuel consumption.

tdc

Sometimes, If I'm coming up to a red light and I'm in third I will put the clutch down, put it in first, but leave my foot on the clutch for and let it roll for a few seconds and then brake. I want to stop this as I don't want to make a habit of it. Is this coasting? Or are you putting it in neutral once you gain momentum?

zod

"You don't say what you do when you go out of gear, but with a manual transmission, you should shift to neutral and not keep your foot on the clutch, that causes more wear on the throwout bearing. Most clutches die from bearing wear than actually wearing out the clutch itself. The bearing can go bad, or it can eat through the clutch pressure plate fingers.
Overall, I think your gas savings probably are about equal to the increased brake maintenance, so keep doing this if it makes you feel good, but it would probably take some top quality scientific methods to prove any savings one way or the other."

http://en.allexperts.com/q/Driving-Driving-Test-2382/Coasting-Neutral-Save-Gas.htm

cyrusdvirus

I deliberately tried it once on a hill near Cobh. Stopped the car at the top of it, gave a little kick in first gear to get rolling. TOTALLY SCARED THE **** out of myself as when i looked at the speedo half way down, I was rapidly approaching 60mph. Not in gear. Felt like the car was running away from me.

Certainly wouldn't recommend it!!

Esel

Crazy, imo. You are not driving the car, merely steering it. What if you have to make a sudden evasive manoeuvre? What if the engine cuts out (and your power steering and brakes go)?

If you have to put the engine back in gear, will you be able to match the revs?

I do not believe that this procedure is recommended by any manufacturer or safety authority.

cyrusdvirus

esel wrote: »

Crazy, imo. You are not driving the car, merely steering it. What if you have to make a sudden evasive manoeuvre? What if the engine cuts out (and your power steering and brakes go)?

If you have to put the engine back in gear, will you be able to match the revs?

I do not believe that this procedure is recommended by any manufacturer or safety authority.

Couldn't agree more! Which was why i stopped the car, and DROVE the rest of the way down. Before that it was as if i was a passanger in my own car.

--amadeus--

vtec wrote: »

coasting in neutral will result in the gearbox turning quicker that its supposed to as the wheels are turning it, while the engine will be at idle (beteen 600-900rpm on average car) and that can give problems with selecting a gear and cause damage to the gearbox in the longterm

I'm sorry but you have totally lost me here

How will the gearbox be turning faster than it should because it's being driven by the wheels rather than the engine? The gearbox will be working at exactly the same speed as if the clutch was engaged will it not, at whatever speed it should be relative to the wheel speed, regardless of where the motive force is from.

And why does the difference between engine speed and gearbox speed make any difference? The OP asked about coasting in neutral so there is no connection between teh gearbox and teh engine so thier relative speeds are irrelevant, aren't they?

As for re-selecting a gear you'd blip the throttle before engaging to match revs and road speed I assume.

Couple of points - I can think of absolutley no way that coasting a car can damage it, as long as you try to match revs before re-engaging the gearbox. Coasting in neutral should not be confused with slipping (or riding) the clutch, where you depress the clutch while gears are engaged so reduce the torque going from the engine to the wheels. This is a very bad habit and causes a huge amount of wear to the clutch pad.

Secondly there is a huge difference between free wheeling down a steep hill (which is dangerous) and popping teh car into neutral so it can roll forward in stop start town traffic.

E92

kdevitt wrote: »

The manual from BMW for the E30 instructed you to coast as often as posisble to help fuel consumption.

Presumably they meant once the car is up to speed, only use the accelerator when necessary. I doubt it BMW are promoting the idea that E30 owners should take the car out of gear and pout it into neutral when driving.

A lot of people are mixing up coasting in neutral with coasting while the car is in gear.

Coasting with the car in gear is perfectly fine, it is very good for saving fuel and does no damage to the engine at all, but putting the car into neutral when the car is moving is NOT fine, wastes more fuel than the method described above, is not good for the engine and very dangerous indeed!

E92

--amadeus-- wrote: »

How will the gearbox be turning faster than it should because it's being driven by the wheels rather than the engine? The gearbox will be working at exactly the same speed as if the clutch was engaged will it not, at whatever speed it should be relative to the wheel speed, regardless of where the motive force is from.

Modern engines are programmed so that if someone puts the car into neutral while the car is moving, the revs stay a lot higher than they normally would if the car was stopped and in neutral. Like if the idle speed was 600 rpm, if you put the car into neutral so as to coast, the car will "idle" at say 1200 rpm.

antodeco

Whenever I put it into Neutral, my revs drop completley. As mentioned, Im not doing it over a mile or anything, its simply coming into traffic lights. I know its a bad habit, but dangerous? Everything you do in a car is potentially dangerous. Im driving in a straight line on a flat surface. How the engine would cut out in neutral is beyond me?

kdevitt

E92 wrote: »

Presumably they meant once the car is up to speed, only use the accelerator when necessary. I doubt it BMW are promoting the idea that E30 owners should take the car out of gear and pout it into neutral when driving.

A lot of people are mixing up coasting in neutral with coasting while the car is in gear.

Coasting with the car in gear is perfectly fine, it is very good for saving fuel and does no damage to the engine at all, but putting the car into neutral when the car is moving is NOT fine, wastes more fuel than the method described above, is not good for the engine and very dangerous indeed!

Eh.?? Coasting in gear?? You have me lost - you're either in gear or you're not.

BMW recommended coasting (in neutral just in case anyone gets confused) to save petrol. Love the way people got scared by their cars getting away from them when they were coasting!! Are they incapable of using the brakes??

cyrusdvirus

kdevitt wrote: »

Love the way people got scared by their cars getting away from them when they were coasting!! Are they incapable of using the brakes??

On the hill i was referring to I HAD to use the brakes. If I had driven (in gear) down that hill i wouldn't have been going quite so fast

E92

kdevitt wrote: »

Eh.?? Coasting in gear?? You have me lost - you're either in gear or you're not.

I always thought coasting just meant leaving your foot off the accelerator pedal and letting the car go on it's own.

Terrontress

Gatecrash. You are saying that BMW recommend that if you are driving down a long gradient, i.e. the hill to the Boyne Bridge; you take the car out of gear, into neutral and let gravity pull the car down the hill instead?

kdevitt

E92 wrote: »

I always thought coasting just meant leaving your foot off the accelerator pedal and letting the car go on it's own.

No - thats driving in gear. You're coasting if you're in neutral, or you have the clutch dipped.

kdevitt

gatecrash wrote: »

On the hill i was referring to I HAD to use the brakes. If I had driven (in gear) down that hill i wouldn't have been going quite so fast

Sounds like your example was just pure bad driving - you let the car roll to 60mph - of course its going to feel like its getting away from you. :rolleyes:

AckwelFoley

--amadeus-- wrote: »

I'm sorry but you have totally lost me here

How will the gearbox be turning faster than it should because it's being driven by the wheels rather than the engine? The gearbox will be working at exactly the same speed as if the clutch was engaged will it not, at whatever speed it should be relative to the wheel speed, regardless of where the motive force is from.

And why does the difference between engine speed and gearbox speed make any difference? The OP asked about coasting in neutral so there is no connection between teh gearbox and teh engine so thier relative speeds are irrelevant, aren't they?

As for re-selecting a gear you'd blip the throttle before engaging to match revs and road speed I assume.

Couple of points - I can think of absolutley no way that coasting a car can damage it, as long as you try to match revs before re-engaging the gearbox. Coasting in neutral should not be confused with slipping (or riding) the clutch, where you depress the clutch while gears are engaged so reduce the torque going from the engine to the wheels. This is a very bad habit and causes a huge amount of wear to the clutch pad.

Secondly there is a huge difference between free wheeling down a steep hill (which is dangerous) and popping teh car into neutral so it can roll forward in stop start town traffic.

Ladies and gentlemen.

This is the only post that makes sence in this thred.
just to add, when you are driving on a road, the engine DOES NOT CONTROL BRAKING.. the breaks do. Where the engine helps is holding control going down hill etc..

If in doubt just read Amaeus's post again

AckwelFoley

Coasting will save fuel, but its a bad habit.



You will fail your dribing test of you do it

milltown

--amadeus-- wrote: »

I'm sorry but you have totally lost me here

How will the gearbox be turning faster than it should because it's being driven by the wheels rather than the engine? The gearbox will be working at exactly the same speed as if the clutch was engaged will it not, at whatever speed it should be relative to the wheel speed, regardless of where the motive force is from.

And why does the difference between engine speed and gearbox speed make any difference? The OP asked about coasting in neutral so there is no connection between teh gearbox and teh engine so thier relative speeds are irrelevant, aren't they?

As for re-selecting a gear you'd blip the throttle before engaging to match revs and road speed I assume.

Couple of points - I can think of absolutley no way that coasting a car can damage it, as long as you try to match revs before re-engaging the gearbox. Coasting in neutral should not be confused with slipping (or riding) the clutch, where you depress the clutch while gears are engaged so reduce the torque going from the engine to the wheels. This is a very bad habit and causes a huge amount of wear to the clutch pad.

Secondly there is a huge difference between free wheeling down a steep hill (which is dangerous) and popping teh car into neutral so it can roll forward in stop start town traffic.

Just for the sake of being pedantic, and for the benefit of Snyper, Amadeus and Vtec, who are all wrong in their own little ways:

When coasting as described previously in this thread, unless the clutch pedal is depressed, the gearbox and engine are still very much connected. The output shaft of the gearbox is turning at the wheel speed divided by the final drive ratio, while the input shaft is turning at engine speed. There could be a large difference between the two shaft's speed's. When a car is driving normally in a gear, the drive is transmitted through the input shaft, to the layshaft, through the selected gear to the output shaft and final drive. All other gears are freewheeling on the output shaft but driven by the layshaft at engine speed.

Only a proper lunatic would be coasting at speeds that would cause these shaft speeds to exceed their normal operating range.

Driving in gear with the clutch depressed will not wear your clutch plate. It may shorten the life of your release bearing but that's about it.

My opinion: It's not going to damage your car but it's not a good idea. Drive smoothly and read the road and other drivers ahead and you'll improve your fuel economy to the point where there's neglible gain to be made from coasting.

Terrontress

It may not damage the car but it is dangerous. It is the drive from the transmission that keeps you on the road. Same reason why you should accelerate round bends.
And to suggest BMW would recommend doing this is a nonsense.

kdevitt

Terrontress wrote: »

It may not damage the car but it is dangerous. It is the drive from the transmission that keeps you on the road. Same reason why you should accelerate round bends.
And to suggest BMW would recommend doing this is a nonsense.

I wasn't suggesting BMW recommended it - I was stating it as fact, which it is.

So tell me a bit more about your accelerate around the corners theory - specifically in relation to FWD cars.

PRND

kdevitt wrote: »

I wasn't suggesting BMW recommended it - I was stating it as fact, which it is.

So tell me a bit more about your accelerate around the corners theory - specifically in relation to FWD cars.

I think he's right.

Read this

http://www.cumbria.police.uk/bikesafe/html/cornering_car_drivers.html

First paragraph.

And when you read that; read this

http://driving.timesonline.co.uk/tol/life_and_style/driving/car_clinic/article3082470.ece

Fifth question down.

I'd be interested if you could provide a verbatim quote from the BMW manual. Maybe you have misread it. I don't doubt you are trying to tell the truth.

copacetic

kdevitt wrote: »

I wasn't suggesting BMW recommended it - I was stating it as fact, which it is.

So tell me a bit more about your accelerate around the corners theory - specifically in relation to FWD cars.

have you got anything to back up your 'fact'? Only in commas as I'm sure like me you see plenty of posts stating things are facts on boards, generaly people like to see the proof themselves, not believe random people on the interweb. (and thats a fact!)

I haven't heard this before and have had a bmw previously with no mention of this in the manual that I remember.

Terrontress

I don't believe it to be fact. Unless it was a misprint but even still, the op should not do it.

And I don't need a website to tell me not to decelerate on a bend. Anyone who actually thinks about what they're doing while driving would know. Maybe devitt has only driven Lincoln Town Cars or something else that's like driving a pillow

here.from.day.1

Just to the posters who said that coasting can save on fuel consumption, when you coast (in gear btw, never tried in neutral) yes the MPG goes up but as you coast you lose speed and then to get back to the speed you were cruising at you would need accelerate harder (bringing the MPG way down) than if you hadn't coasted, thus cancelling out any fuel saved, no?

--amadeus--

milltown wrote: »

Just for the sake of being pedantic, and for the benefit of Snyper, Amadeus and Vtec, who are all wrong in their own little ways:

Wow, someone even more pedantic than me!

Of course you're right - the layshaft will still be spinning at engine speed, but that's getting a bit arcane and technical for this discussion isn't it? For the purposes of simplicity there is no connection between engine and wheels when the car is in neutral and the fact that they (and by extension different gearbox elements) are spinning at different speeds is not going to cause any damage, which is the point I was trying to make.

I'm afraid I'll disagree with you on the amount of wear that riding the clutch causes. It can and does damage the clutch pad, both through excessive wear of the friction coating and through the excessive temperature that can build up within a heavilly slipped clutch ("cooking the clutch") which also damages the coatings. Again you are right on the damage it will cause to the release bearing which is not intended for continual use - it's bad full stop!

I can't see any reason why somoeone would coast in nuetral in free flowing traffic, driving in the right gear and maintaining a constant speed will be better than accelerating, coasting and accelerating (as well as being safer). But rolling to a halt in city driving isn't dangerous.

And just to prove that I am equally pedantic (;)) you shouldn't "accelerate around a bend". It's better to be "slow in, fast out", brake on the approach and accelerate only from the apex of the bend. In normal driving holding a constant throttle will keep the car balanced and is the most "sensible" way to drive.

Terrontress

To be even more pedantic, maintaining constant speed is accelerating relative to the car's natural state.