Unintended acceleration

Brett Dikeman brett.dikeman at gmail.com
Wed Oct 21 18:53:34 PDT 2009

On Wed, Oct 21, 2009 at 8:52 PM, Ed Kellock <ekellock at gmail.com> wrote:
> An interesting read... it discusses vacuum assisted braking systems and the
> inability of a car's brake system to stop it at full throttle, regardless of
> assist.

Except it's a load of crap; they all have check valves, and brakes are
MUCH stronger than engines.  Think about the kind of torque you'd need
to get from 0-60 in 150 feet.  That's barely across a large traffic
intersection.  Yet, your brakes can do the opposite handily...

My 'R has vacuum-assisted brakes.  I assure you, they work very well,
including full-throttle-to-hard-braking transitions.  Even if the
engine shuts off, there is an auxiliary vacuum pump which kicks in any
time the ignition is on and vacuum pressure drops.  I was bored one
evening waiting for someone and played with it- you have to work
pretty hard to use up the vacuum faster than the pump can replace it
and exhaust the vacuum reservoir.  That's better than the hydraulic
assist, technically- two completely independent sources of brake

It's also curious why the car, which surely was throttle-by-wire,
didn't shut off the throttle when the brake was applied.  That's very
common behavior, has been for nearly a decade.  Why didn't the driver
attempt to put the car in neutral, switch off the ignition, etc?


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