Freewheeling to save money

Bongles

alastairq wrote: »

Because the wheels & tyres are intended for gripping the road surface.

Therefore if they don't grip the road surface, there is a 'loss of control'....ie, a skid.

There's a loss of grip, but if that loss of grip is intentional and the car goes where the driver intended, when the driver intended, pointing the way the driver intended, that is the very definition of the driver being in control.

alastairq wrote: »

Whether that input is intentional [as with rally drivers using the skid to scrub off speed and point the car in a new direction]...or unintended...the fact that the wheels/tyres are not doing what they are intended for, means a control-loss.

Quick search of YouTube and I found this silliness. I didn't bother with the sound - probably all annoying and American - but watch, for example, 1 minute 30 to 2 mins 10. The driver and rider do not appear to be out of control of their skidding vehicles.

alastairq wrote: »

As I have said, where a skid is deliberately induced, the skill of the driver [at vehicle control, not interaction with other road users....let's not confuse the issue?]......lies with managing that loss-of-control.

A driver uses their skill at vehicle control when they are not in control? That's a non-sequitur.

Retrogamer

I know coasting / freewheeling won't save fuel on a modern petrol car due to the ECU cutting fuel on the over run but what about diesel cars?

Weird_Nev

Bongles wrote: »

There's a loss of grip, but if that loss of grip is intentional and the car goes where the driver intended, when the driver intended, pointing the way the driver intended, that is the very definition of the driver being in control.

You're (deliberately I suspect) confusing the point.

A car has an envelope of grip. Within that envelope of grip, the driver has full control over the car.
Once that grip limit is exceeded, through skidding deliberately or accidentally, the car is NOT 100% under control. The car has momentum, and can alter it's attitude speed and direction only within a prescribed arc. The speed and angle the driver has entered the corner dictates to a large degree the trajectory the car will take through it. They can modify it, slightly, but by and large once you slew a car into an arc like that, it's a done deal where it ends up.

Consider also the factors under control: To drift successfully and safely, you need a track, with a smooth surface, with a known camber and limited obstruction and big run off. You need a huge amount of practice operating outside the grip envelope of the car. The damage sustained by drift vehicles shows how frequently the drivers get it wrong! Even WITH their amazing car control skills.

We don't have the luxury of such a controlled environment on the road. We need to retain as much of that grip envelope in reserve as possible so that we can react and use ti to deal with emergencies.

Where am I going with this?

Keeping the engine connected to the road is a big part of that. DO NOT coast with the clutch out, for any reason. Saving fuel comes after safety, and rolling along without the engine connected to the wheels is a big safety risk. It drastically reduces your ability to react to a hazard or change the course and speed of the car quickly.

No one with any kind of advanced driver training will ever advocate coasting.

Anyone with formal advanced driver training and qualifications care to put their hand up in this thread?

Bongles

Weird_Nev wrote: »

You're (deliberately I suspect) confusing the point.

Whatever I'm confusing, it's certainly not deliberate. I just don't understand what alastairq means when he says 'control' - nothing more sinister than that. In his last post he appeared to contradict himself so I'm not sure he knows either.

Weird_Nev wrote: »

A car has an envelope of grip. Within that envelope of grip, the driver has full control over the car.
Once that grip limit is exceeded, through skidding deliberately or accidentally, the car is NOT 100% under control. The car has momentum, and can alter it's attitude speed and direction only within a prescribed arc. The speed and angle the driver has entered the corner dictates to a large degree the trajectory the car will take through it. They can modify it, slightly, but by and large once you slew a car into an arc like that, it's a done deal where it ends up.

I simply don't agree that the definition of being in control has to include being able to instantly alter the trajectory of the car at all times. One could make an informed, planned decision to temporarily relinquish that ability and still be 'in control', as long as one can reasonably expect not to need that ability for that time - in the same way that I routinely make planned, informed decisions to relinquish the ability to stop within the 30mph stopping distance by driving faster than 30mph.

Weird_Nev wrote: »

Anyone with formal advanced driver training and qualifications care to put their hand up in this thread?

:hello:

If you've taken anything I've said in this thread as advocating skidding or coasting on the public highway then you've misunderstood me and I apologise for being unclear.

WTFH

Retrogamer wrote: »

I know coasting / freewheeling won't save fuel on a modern petrol car due to the ECU cutting fuel on the over run but what about diesel cars?

If you're talking about modern diesel cars, same rule applies. The ECU will cut the fuel if none is required

Weird_Nev

Bongles wrote: »

I simply don't agree that the definition of being in control has to include being able to instantly alter the trajectory of the car at all times. One could make an informed, planned decision to temporarily relinquish that ability and still be 'in control', as long as one can reasonably expect not to need that ability for that time - in the same way that I routinely make planned, informed decisions to relinquish the ability to stop within the 30mph stopping distance by driving faster than 30mph.

Introducing drifting as an example of "car control" that is outside the norm just doesn't make sense to me in terms of this discussion.

Yes, it's impressive. Yes, they clearly can control cars in a manner that most of us are not familiar with. HOWEVER, they trade off a huge number of factors for the sake of going sideways and making smoke. Whilst they do have control of the car, they also have control of the circuit, i.e. they know which way it goes next, the opponents (if any) and the set up of the car.

As I said, the rate at which they get it wrong and go through car bumpers, or just plain cars, is testament to the fact they are operating on the very limit of control over a car. That is after all the very basis of the "sport". They get it wrong, and they have no margin for error.

We're all fallible, we all make mistakes, and yet we somehow have to safely pilot our cars from A-B in sometimes very difficult conditions with a bunch of other unpredictable road users.

That's why we need the fullest possible control over a car, and that's why we shouldn't coast (or drift) on public roads.

Bongles

Weird_Nev wrote: »

Introducing drifting as an example of "car control" that is outside the norm just doesn't make sense to me in terms of this discussion.

You need to take that up with Iceweasel - see post #32.

Weird_Nev wrote: »

Yes, it's impressive. Yes, they clearly can control cars in a manner that most of us are not familiar with. HOWEVER, they trade off a huge number of factors for the sake of going sideways and making smoke. Whilst they do have control of the car, they also have control of the circuit, i.e. they know which way it goes next, the opponents (if any) and the set up of the car.

I quite agree, and I note that the bits I've emboldened there are in agreement with my point and are contrary to

alastairq wrote: »

An induced skid is a deliberate loss of control.

I rest my case .

WTFH

So, to bring this back on topic, should we freewheel in neutral when skidding, be in a gear with foot on clutch, or be in an appropriate gear for the wheel speed?

Also, what is the most economical way to skid?


(actually, I know the answer to that one - In a rental car)

Weird_Nev

WTFH wrote: »

So, to bring this back on topic, should we freewheel in neutral when skidding, be in a gear with foot on clutch, or be in an appropriate gear for the wheel speed?

Also, what is the most economical way to skid?


(actually, I know the answer to that one - In a rental car)

You can clutch kick it to induce the rear wheel skid, but you quickly need it back in gear to maintain the power to the rears and keep them smoking.

And Maccy D's trays under the rear wheels in a FWD car, handbrake on. Cheap as chips.

INcidentally, When drifting only the rear wheels are skidding. It's when the front wheels lose traction that you've got real problems: no directional control.

anotheruser

Another question to consider is would you prefer to put more strain on the engine (slowing down in gear) or the brakes (slowing down out of gear). Although for the brakes, you will still use them to stop no matter if you are in or out of gear.