'Coasting'

by **ericonabike** » Thu May 22, 2014 10:49 am

I put this in inverted commas as I'm not sure what the correct expression should be. I'm talking about the occasions when you take your foot off the accelerator and let engine braking slow you down. It's not 'coasting' as that involves disengaging the engine. So what is it called?

I ask as I drive a Mercedes E220 fairly regularly for work, and it has an Ecometer. It has three horizontal green bars, with the max score being to keep them at 100%. They are: acceleration, constant and....coasting! Looking it up in the manual shows that their definition of coasting is foot-off deceleration, so it seems that they don't know how to describe it either.

And just to go off on a slight tangent, I can regularly get 100% on the first two indicators, but less than 50 on 'coasting'. Seems ironic, as when I'm driving my own car [manual] I pride myself on minimal use of brakes. Seems much harder to do that in an auto, as it doesn't slow down so quickly and I also need to brake harder as the engine seems to be working against me.

Thoughts?

by **Gareth** » Thu May 22, 2014 10:57 am

ericonabike wrote:when I'm driving my own car [manual] I pride myself on minimal use of brakes. Seems much harder to do that in an auto, as it doesn't slow down so quickly and I also need to brake harder as the engine seems to be working against me.

Auto gearboxes seem to move to the highest possible gear when there is little load, worse when there is no load. You can defeat this by using a manual over-ride - then when you lift off the gear is more likely to be one that is appropriate to the speed you are going, and you'll find more 'engine braking' ...

by **GJD** » Thu May 22, 2014 10:57 am

ericonabike wrote:I put this in inverted commas as I'm not sure what the correct expression should be. I'm talking about the occasions when you take your foot off the accelerator and let engine braking slow you down. It's not 'coasting' as that involves disengaging the engine. So what is it called?

Isn't it usually just called engine braking?

by **ericonabike** » Thu May 22, 2014 11:01 am

Engine braking is what is happening, not what you are doing. You couldn't say 'I am now engine braking'?

by **GJD** » Thu May 22, 2014 11:20 am

ericonabike wrote:Engine braking is what is happening, not what you are doing. You couldn't say 'I am now engine braking'?

I think you could - in that if you did say that, I think people would know what you meant

. But if you didn't want to say that, could you say you had 'lifted off', or were 'using engine braking'?

by **martine** » Thu May 22, 2014 11:22 am

Using 'accelerator sense'? (or 'acceleration sense' in Roadcraft terminology).

by **trashbat** » Thu May 22, 2014 11:41 am

It's not something I often talk about, so I don't fuss over semantics, but I'd define coasting as being off the throttle. Engine braking is just another force slowing you down, like rolling resistance or gravity, so why not lump them all together.

It's my limited understanding that modern automatics sometimes put the car into neutral because it's the most efficient option at that moment.

Do we only frown upon being in neutral in a manual car because of the human element?

by **GJD** » Thu May 22, 2014 11:51 am

trashbat wrote:Do we only frown upon being in neutral in a manual car because of the human element?

I think you might be right. We don't frown on BGOL when an automatic does it as part of the normal behaviour of the machine.

by **ericonabike** » Thu May 22, 2014 3:23 pm

It's more than semantics. I had to take a local council's theory test as part of my private hire licence application. One of the questions was 'when is it acceptable to coast?' Answer being never, on the basis that it means freewheeling, effectively.

by **Carbon Based** » Thu May 22, 2014 7:35 pm

trashbat wrote:It's my limited understanding that modern automatics sometimes put the car into neutral because it's the most efficient option at that moment.

I can confirm that ours does just that.

by **fungus** » Thu May 22, 2014 9:11 pm

Coasting is where the drive is disconnected from the road wheels, eg. gear engaged but clutch depressed, or no gear engaged. What erionabike is describing, is, according to the DSAs Driving the Essentiel Skills, over run.

by **cupraray** » Sat May 24, 2014 8:26 pm

Nigel has the last word ...its called over-run

by **TripleS** » Wed May 28, 2014 5:18 pm

cupraray wrote:Nigel has the last word ...its called over-run

Exactly. So-called 'coasting' is one of numerous things over which we tend to be prone to knicker knotting. So long as, one way or another, we retain a suitable capacity for braking, does it really matter how we provide it? I don't think it does, but other views are, as usual, available.

Best wishes all,
Dave.

by **Ancient** » Wed May 28, 2014 5:31 pm

Of course some cars (Prius for example) do actually coast - hence the additional option of 'B' on the 'gear stick'.

(For those who don't know, a Prius has
D = drive when you push on the go-pedal, coast when you don't
R = reverse
N = neutral
B = drive when you push on the go-pedal, keep engine engaged for engine braking when you don't)

by **TheInsanity1234** » Wed May 28, 2014 6:15 pm

I know that on some Audis, when you've been maintaining the same speed for a little while/you're running on cruise control, the auto-box will somehow reduce the contact between the engine and the gear-box so that it eliminates a large proportion of engine-braking, and it increases fuel-efficiency as there is less friction from the engine.

I have no idea how it works, but I saw it mentioned in the handbook of a friend's Audi when I was reading through it.
(Yes, I do like to read the car's handbook, even when it's not mine! :lol:

)

'Coasting'

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