On Fri, 2008-04-18 at 16:26 +0100, Michael Rigby-Jones wrote:
> Electric pumps have been around for a while, my 1993 MR2 Turbo used one.
> Apart from giving more flexibility in locating the pump, the pump motor
> speed can be varied according to the cars speed to provide variable
> assistance.

I didn't know they went that far back!

Electric PS pumps also end up saving you fuel.

The most assist is needed at very slow speeds, i.e. in a parking lot. At
highway speeds one barely needs any assist.

With a mechanical pump it needs to give the most assist when the engine
is turning at the slowest RPMs. This results in a pump that's basically
"oversized" for all conditions except parking!

By varying the assist with an electric pump you still have to size the
pump for the maximum assist, but you only run it that way when needed. 

For larger vehicles I'm sure the difference is almost un-noticeable, but
on smaller cars the difference can be quite large.

TTYL
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