proportioning valve effectiveness - was monkeylads

[Livolsi, Stephane]

Ok, I understand now.  Thanks

Stephane

> ----------
> From: 	Bernard Littau[SMTP:bernardl at acumenassociates.com]
> Sent: 	August 19, 2003 5:35 PM
> To: 	Livolsi, Stephane; 'Audi Quattro List'
> Subject: 	RE: proportioning valve effectiveness - was monkeylads
>
>
> > That's right there is only one channel going to the rears!  I am
> > enlightened!
> >
> > Now taking this one step further (if you don't mind) ...
> >
> > Just how effective (accurate?)can the proportioning valve be?
> > My first experience with a proportioning valve was on my 82 Toyota 4X4
> > where
> > I had to make some modifications because of the lift kit I installed (2"
> > lift)  I learned a bit about the system then and I recall thinking this
> is
> > pretty goofy.  Under braking, the relationship between the body and the
> > axle
> > changes due to the nose of the vehicle dipping and I guess the rear
> > lifting,
> > which activates the lever and reduces the brake fluid flow to the rears
> so
> > they don't lock up.  Seems pretty imprecise.  Looking at the valve on my
> > 5ktq, it isn't a whole lot different in design than the toyota.
>
> Way more accurate (and precise :-) than you might think.
>
> Given the standardization of the parts and the predictable behavior of
> say,
> the brakes, the lever length and spring rate are very likely to be
> specifically tuned for each model of car.
>
> Consider distributors of tens of years ago:  Ignition advance was done
> mechanically through centrifugal force (rpm) acting on lobes and springs
> on
> an eccentric cam gear.   The advance curve was specific to the application
> (car, engine model and target octane).  These curves, and their
> reproducibility from car to car, were very good representations of an
> optimal advance curve (factoring in some safety margin).
>
> Best,
>
> Bernard
>
>