Freewheeling to save money

colino

Anyone with an ancient carb car can save fuel by buying a little device that collapses the huge vacuum in the inlet manifold on the overrun - that in effects sucks excess fuel into the engine. You could instead though just buy a better car.

alastairq

You could instead though just buy a better car.

Better than what?

Given the endless moans & complaints of faults reported on here, and elsewhere, regarding 'new' cars, I'm not convinced we are really 'better' now than 30 or so years ago?

almillar

Some confusion and bad advice in here, let's try to clear it up.
For 'L' test standards - do not coast. You are not in full control of your vehicle, and you should slow down in gear. As above - slowing down in gear in a fuel injected car (any petrol since 1993 ish at least) uses no petrol. The engine is constantly being bump started by the road!
That's not the whole story though. Coasting/Freewheeling isn't as bad as is made out in the 'failsafe' version above. You're not on full control, the car can speed up down a hill, and you really shouldn't 'roll' around a corner, you should have your foot on the throttle throughout it. With those caveats out of the way, you can then use coasting to your advantage, if you actually concentrate on your driving.
You need to think ahead, and think about how quickly you want to slow down.
Do you need to
a) use the brakes (and engine)
b) use just the engine
c) use neither - coast/freewheel
Slowing down with the brakes is the fastest way to stop. I hope that doesn't need any further explanation. Keeping the car in the gear you're in until near stall point (no fuel used), helps the brakes out and keeps you in better control. Going down through the gears is a waste of time unless you're racing.
Slowing down in gear causes the engine to slow the car down through friction - engine braking. The lower the gear, the greater the retardation (you slow down faster). No fuel will be used whilst doing this.
Coasting then, is for when you no longer need the throttle, but don't want to slow down as much as you would with engine braking. Whilst coasting, your engine is idling, as if it's sitting at the traffic lights. It's better (or smoother and more fuel efficient at least) to coast to a halt at the right time, than to engine brake, slow down too quickly, then have to accelerate again.
It's about maintaining momentum.

Bongles

almillar wrote: »

Coasting then, is for when you no longer need the throttle, but don't want to slow down as much as you would with engine braking.

Is there a real life example you can give to illustrate when you might do this - slowing down off brake, off throttle and out of gear (or clutch down at least)?

Mankysteve

alastairq wrote: »

Better than what?

Given the endless moans & complaints of faults reported on here, and elsewhere, regarding 'new' cars, I'm not convinced we are really 'better' now than 30 or so years ago?

Have you actually taken look a car produced 30 years ago. How long they
Lasted, how reliable they were or safe. Don't get me wrong I'm a classic fan but modern car are more reliable, last longer, give better mpg, are less polluting and safer than cars 30 years ago.

I think you need to take road tinted specs off.

anotheruser

A really good topic and one that I am interested in as I do "free-wheel", but that's not really my fault.

I used to own a 1967 Beetle where I picked up the habit of free-wheeling to save fuel and cut the work on the engine. It's sort of carried on to my other two cars:

A 51 plate Ford Ka - 127,000 miles (although only says 27,000 :P)
A 56 plate Ford Focus - 88,000 miles.

The Ka has a workhorse engine which seems to show no sign of giving up. It is also nearly as loud, if not louder than the Beetle. By free-wheeling, I am giving the engine (and my ears!) a bit of a rest. The Focus doesn't matter either way as it's pretty quiet.



The argument of "un-safe" I don't quite understand.

If I am travelling at 40mph in 4th, which is acceptable under "normal" driving conditions, If I needed to accelerate out of danger I would be in completely the wrong gear to do so and would save less than half a second.
Therefore I don't consider this to be a reason to stop doing it.

A friend of mine suggested if travelling in snow and you run into black ice and loose stopping ability then being in gear will enable you to accelerate and keep your car from skidding.
Perhaps this is right but I've skidded a few times in snow / compacted snow and ice but being in gear wouldn't help get out of that. Plus I've not had a patch of black ice long enough to be skidding out of control.

Surely it is no more un-safe than "free-wheeling" on a bicycle as you can't accelerate out of danger then either.

Bongles wrote: »

Is there a real life example you can give to illustrate when you might do this - slowing down off brake, off throttle and out of gear?

> Perhaps coming up to a queue of traffic / traffic lights (on red) that you can see in the distance with nobody behind you?
> Slowing down for a speed limit, which has a roundabout or traffic lights (on red) within throwing distance of the sign?



But I am happy to try to understand more... please don't belittle me for this habit, go poo poo a smoker as they are endangering more people! :P
And please don't quote the whole post like poster 21 - just quote the bits you're replying to.

Bongles

anotheruser wrote: »

If I am travelling at 40mph in 4th, which is acceptable under "normal" driving conditions, If I needed to accelerate out of danger I would be in completely the wrong gear to do so and would save less than half a second.
Therefore I don't consider this to be a reason to stop doing it.

I know what you're getting at but I think there's a bit of a discontinuity in your reasoning there. If 40 in 4th is acceptable under "normal" conditions and 40 in 4th does not give you the flexibility to accelerate out of danger, then a situation in which you anticipate that you might need that acceleration does not fit that definition of "normal" conditions. That's fine - it just means that if you do anticipate that need then you need to be in a lower gear - not in 4th and not freewheeling either. Where you don't anticipate that need for the time being (i.e. "normal" conditions as you implicitly defined it, whether you intended to or not:)) then 4th will be fine, as will, by your argument, freewheeling.

anotheruser wrote: »

> Perhaps coming up to a queue of traffic / traffic lights (on red) that you can see in the distance with nobody behind you?
> Slowing down for a speed limit, which has a roundabout or traffic lights (on red) within throwing distance of the sign?

You've answered the question I posed to almillar there (which is fine ). He had said:

almillar wrote: »

Coasting then, is for when you no longer need the throttle, but don't want to slow down as much as you would with engine braking.

I've added the bold to the last bit there because it's important. As I understood it, he was talking about coasting achieving all the required deceleration.

I often find with things like traffic lights, roundabouts and speed limits that, whilst I lift off to start slowing down, engine braking alone is not sufficient to achieve all the deceleration I need and so I use the brakes too. To answer the question, we need not just to find an example where the hazard is apparent early enough that you can achieve all your deceleration through engine braking, but one where the hazard is apparent so early that you can achieve all the necessary deceleration through coasting alone. Not only that - it needs to be a situation where starting to slow that far in advance is not an unreasonable thing to do.

Gloomendoom

'Freewheels' used to be fitted as standard to some cars. Rover claimed a 15% fuel saving.

alastairq

Have you actually taken look a car produced 30 years ago. How long they
Lasted, how reliable they were or safe. Don't get me wrong I'm a classic fan but modern car are more reliable, last longer, give better mpg, are less polluting and safer than cars 30 years ago.

I think you need to take road tinted specs off.

Don't misunderstand me, I'm fully aware of what are now seen as 'shortcomings' of older cars [however, a point to note, these 'shortcomings' weren't seen as such 30 years ago.....]....compared to present day new cars....however, if its shortcomings we are focussing on, today's cars have just as many [what I see as 'unacceptable'] faults.....but these faults are of a different nature to those of a new car, 30 years ago.

In the end, a new car 30 years ago did exactly what a new car does today....got us from A to B in comfort, and safety as we knew it/know it.

With a relative cost factor.

Rose-tinted specs I do not have, but I am equally as realistic about today's offerings as I am of cars from 30 years ago.....same horse, different clothes.

alastairq

A friend of mine suggested if travelling in snow and you run into black ice and loose stopping ability then being in gear will enable you to accelerate and keep your car from skidding.
Perhaps this is right but I've skidded a few times in snow / compacted snow and ice but being in gear wouldn't help get out of that. Plus I've not had a patch of black ice long enough to be skidding out of control.

Not true...and goes against everything taught by instructors who deal with skid control & recovery.

All skids are a loss of control.....even if done deliberately [a deliberate loss of control]...


The biggest issue with regards to 'coasting' concerns what might happen when drive needs to be taken up again?

Unless the driver has enough knowledge to realise that, before releasing the clutch pedal, the engine revs should already be somewhere near the figure for that gear, at that road speed....then there is a risk of sudden unwanted deceleration as the road wheels force the engine revs to rise, reluctantly.

There is a possibility that this alone could put the vehicle into a skid.

Another aspect of coasting [if doing so in neutral] is the ability to actually acquire the correct gear, when the driver needs to.

There is a risk of not getting a gear..or indeed, the right gear.....only realised once the clutch is beginning to engage.

A distraction at the wrong time, or an inexperienced driver, and any of the above could easily occur.

SAAB were renowned for fitting a freewheel device to their 95 & 96 range....[as were several East German manufacturers...Wartburg for one].... as an economy device.

When engaged, once the gas pedal was released, the freewheel took over...however, drive was re-engaged as soon as the gas pedal was brought back into use.....without a shock or jolt to the transmission.

Took a bit of getting used to, to find one wasn't slowing down as one thought one should, when off the gas...