On 7/26/13 4:25 PM, Walter Bright wrote:
On 7/26/2013 4:07 PM, Andrei Alexandrescu wrote:
On 7/26/13 3:52 PM, Walter Bright wrote:
Although commonplace, it is poor practice to use the engine to slow the
car down (unless you're dealing with brake fade from overheating).
I know next to nothing about cars so take this destruction with a
grain of salt.
1. Brake pads are cheap compared with engine rebuilds.
My understanding is that engine brake does not destroy the engine. It
does not
involve friction.
It's news to me that engines are frictionless! (The braking effect is
only partially due to engine friction - the pumping of the air is most
of it. But the engine WEAR is due to friction.)
Indeed Wikipedia agrees:
http://en.wikipedia.org/wiki/Engine_braking and even mentions "Engine
braking is
a generally accepted practice and can help save wear on friction brakes".
Of course it saves wear on the brakes. The issue is do you prefer wear
on your engine?
2. Using the engine as a brake can cause unburned gas to wash the oil
off of the cylinder walls, resulting in excessive wear.
[citation needed]
Mechanics at the dealer told me this. They had no reason to lie to me.
3. The engine is not designed to be a brake. Use the brakes. Brake pads
are not precious :-)
Engine brake is a natural artifact of its design. I don't think you
can build an
argument around "wasn't design to do that, so don't". Engine braking is a
widespread and common technique.
I agree it is widespread and commonplace. That's why the mechanics felt
it necessary to tell me not to do it. I was also told not to do it when
I took two different courses in track driving - the Bob Bondurant and
Skip Barber ones.
I use engine braking most of the time (I always drive manual so that's
easy).
Saves gas and I've never had a mechanic tell me "you better go easy
with that
engine brake, look at them cylinder walls!" My brake pads reach a
state of
immortality.
The object isn't to save brake pads, it's to reduce the wear and tear on
your engine.
I stand by my opinion and practice, and I consider yours completely
unsubstantiated, to the extent it doesn't need further rebuttal. FWIW
I've heard stuff from mechanics (about e.g. how ABS works) that would
make a physicist blush.
Andrei
