A proper language comparison...

[Jordi Sayol]

On 27/07/13 01:25, 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.

This absolutely true. About twenty years ago my friend's car broke down in a remote location. To bring the car to the nearest mechanic (2 or 3 kilometers), tied it to another car with a rope and used engine braking without ignition (engine was damaged) to prevent the spring effect. Result, pistons melted by excessive friction. This was due to the effect that Walter's mechanics clearly explained.

> 
> 
>>> 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.
> 
> 

-- 
Jordi Sayol