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RE: braking 101 (short)
200 lines to read. sigh....
> Date: Wed, 21 Oct 1998 12:10:11 EDT
> From: QSHIPQ@aol.com
> >flame bait to one side.....
> >"on corner entry" meant just that. not (power on) cornering. throttle
> >going into the corner. in this "mode" the braking torque to the front
> >wheels is *increased* (rotating at higher speed), and the braking torque
> >the rears are decreased (rotating at a lower speed)...
> Reread that statement. Are you sure you have this correct? If the front
> wheels are rotating faster than the rears, where does engine braking
> Trg go?
yes i'm sure scott. the torsen under "coast" throttle conditions does *not*
act the way it does under acceleration. you need to re-visit the theory of
operation. the maths on the bias ratio under braking (coast throttle) is
interesting. the zexel folks spent a lot of time to ensure that the torsen
shifted torque under coast throttle conditons. once again, happy to supply
references since you're clearly struggling here...
> >the point is that the quattro with torsen is able to *remove* engine
> >force from the rears. this has 2 effects: -
> >1) putting more engine braking through the tyres in the front where the
> >adhesion is, and
> >2) leaving more rear tyre adhesion for braking.
> 1) Sounds good, would you want that if the maximum braking weight
> distribution is 50/50 in the quattro? What would you need to do to get a
> better actual braking distribution? What does this mean to those
> springs and braking upgrades to their quattros? Those with proportioning
> valves? Those with ABS? Those with ABS and Torsens? What does an open
> do with engine Trg and braking? 2) Given that total braking in the back
> - -/= 22% in a quattro, you need ALL the "more rear tyre adhesion for
> you can get. I'm with you all the way here.
> However Mr. Ilkays' point remains. Mass of quattro (all other things
> equal), and where that mass is. Translate this to a street quattro, it
> only send 22% of it's braking force to the rear of the car, this point
> lost in the mass of the car (and the corresponding lack of mass in the
> brakes). Add to this, a street car has ABS, both the rwd and the awd car
> brake as close to the ideal as the hardware and weight distribution
> That's a loss to a front heavy abs car with tiny rear brakes when compared
> a more evenly distributed rwd car.
no, once again you're missing the point. the point is that the quattro
sends less engine braking torque to the rear leaving more rear traction for
actual braking. this is a win. references from zexel are numerous. look
> No, in "coast" mode there is no differentiation, that's 50f/50 r, that's
> If the rear goes into O the torsen will not "remove" (sic) torque from the
> rear until the rear DRIVESHAFT (the ones between the f & r diffs) is
> as or faster than the front.
wrong. once again you don't know how a torsen operates. mind you there
are various models and they do have some different features.
> >so, by definition better awd braking than a locked centre car (forced to
> >send 50% braking torque rearwards), and less propensity to snap oversteer
> >than the generation 1 car.
> Incorrect statement. See above. What happens when the fr/r braking
> distribution exceeds 22%r? Like in a 90q under braking. Dave, not sure
> is worth discussing yet. You don't understand chassis dynamics and
> No big deal, it just makes for a tough discussion. You don't have the
yada yada yada....
[snip a hundred lines]
one final statistic: once again, sorry to let the facts get in the way of a
good meaningless discussion, but what do you think is the reason that the
new s4 brakes better than the e36 euro m3 evo 2 (source autocar 60mph to 0
luck perhaps? flaky stopwatches? myopia?
end of discussion...