"NY" wrote in message
o.uk...
"Dave Liquorice" wrote in message
idual.net...
On Tue, 24 Jul 2018 00:14:28 +0100, Dave Plowman (News) wrote:

But why would you bother when it's simple to just turn off the ignition?

'cause a diesel, burning it's own oil, will just carry on switched
off or not... B-)

Surely the important thing is to get the car to a standstill as safely
as possible?

So just use the foot brake a bit harder than normal to bring both car
and engine to a safe and controlled standstill.

The orginal start of this thread was based in the US. They mostly
drive automatics over there so the pigging thing will change down to
counter act the braking. Selecting N still doesn't strike me as
"right" though, selecting the highest fixed drive and braking ought
to work. Assuming the auto box and/or computers will allow that
change to happen with the engine under full throttle.

Yes, the whole concept of removing the mechanical load from an engine that
is running out of control seems counter-intuitive, when the object would
seem to be to remove the problem at source by cutting off the fuel which
is best achieved by turning off the ignition. That hinges critically on
not accidentally locking the steering wheel: the thing that the video said
was highly likely but people on this thread have said doesn't happen until
the keys are removed - unless anyone knows of exceptions to that for
certain vehicles.

Braking the engine when it is transmitting power to the wheels will lead
to a "fight" between brakes and engine, with the risk that the energy that
the engine is generating will heat up brakes too much. If you have an
engine generating maybe 100 hp, you've got to dissipate that sort of
energy in the brakes. What is the effect of the discs heating up
dramatically: can it cause loss of braking force?

Yep, same effect as brake fade when using them when going
down a long downhill run and using the brakes in that situation.

They did mention something about "burning out the brakes" which was the
reason for contemplating using the "emergency brake" instead, as if that
magically used different pads and wouldn't be affected in exactly the same
way by brake heating.

Yeah, they don't seem to have much of a clue about the basics.