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Re: A New Look at Torsens + Events vs nonevents
>I don't think we'd go to that level. That said, though, there _are_
>serious differences in road surfaces between, e.g., Germany and the UK.
>Both are normally pretty smooth, but their interaction with the tyres
>seems very different.
Problem: A torsen is fooled into appropriating torque by slip angle
differences while accelerating in a turn. "Road surface" is irrelevent, cf
'might' be, radius is, weight is, and rate of acceleration is (all found in
Dave E's paper).
>The most promising opening I know of at present is the specification of
>the alignment job itself, _NOT_ the actual numbers used. Hints have
>suggested it's a 'less than one hour' job for US dealers, whereas Audi
>in Europe allows two hours and BR Motorsport frequently take three.
Careful on what was said. IMO, if one can replicate the numbers 'your'
mechanic got on your car (still looking for them?) in 20 minutes, what does
it matter? A guy that does alignments for a living only, will beat me and
your wrench every time, in calibration and execution, btst. I know how to
calibrate (it ain't rocket stuff), I'm just slower. The US dealers are
allowed the same book as the UK dealers, doesn't mean "either" takes it, or
"either" beats it. Bob Duprees alignment at an independent took 8.5 hours
(and we drove from chicago to CO with no tire wear and a straight wheel
before hand). What if I took 5 hours? It's not relevent. The "NUMBERS"
are, and in deference to getting 1100 single dollar bills :), easily
replicatable, I get alignment requests every week.
In regards to events v nonevents, those are already in the archives. Jeff G
and I have had several discussions on the subject, and really agree, neither
a *non event* or experiencing an *event* doesn't matter, and we both easily
accept personal anecdotes on either side - Jeff even says non events might
happen, in his description. All one has to do is understand that it *can*
happen. Then we are happy with our events as a nature of the device, and
Phil and Dave's non-events as a possible nature of or reaction to the device.
Dave E's reference sae 885140 did a study on slip angles while accelerating
and turning in dry pavement, and found "CONCLUSIVELY" that relative slip
angles do make the torsen shift torque, and *can* up to the Maximum Bias
Ratio = 75r/25f. Reread the "hot turning in a quattro" I posted, and Jeff's
spider bite post. We have already addressed the possibility that nothing
catastrophic happening is possible. Theories on that are pretty easy. A
true race turn allows for no "increased" steering correction towards the
apex. Also remember, the torsen, "during" *any* turn, is allocating torque
based on the radius and conditions (speed, cf, etc) of 'each' turn
differently, by definition. Predicting that is impossible every time.
Reacting to it, is a different argument. However, you also will be passed by
a totally predictable locked diff on the same cf, btdt, btst.
If Phil answered my questions posed in the "Alignment" thread, and Dave
presented his Torsen 885140 quiz to the list, we'd quickly realize that Dave
would have to disagree with Phil. Pretty cool, IMO :).
One could just ask, which alignment specification/s was so far out, that
relative slip angle torque allocation was *not* happening. Pretty tough
argument to make, I'd further say, impossible.
Bottom Line: If a center torsen allocates torque based on relative slip
angle AND/OR traction arguments (see 885140), alignment is specifically
irrelevent. Think of this idea in terms of alignment, the test performed in
885140 were with a fully loaded ("maximum permissible load" - not curb
weight) 80q in the accel/cornering test (remember, a 1/4 tank of gas and no
load is alignment protocol), one has to wonder what *those* exact
"specifications" were. I might argue "irrelevent" (we could certainly argue
"max load" and a bunch of other "givens" were more important variables to the
vailidity of that paper). No mention of an alignment done before hand.
Happy to address it, however, we just need the before and after numbers and
work performed before and after from Phil to even consider it's relevency.
We could take the next virtual step, and walk thru the effect of specific
alignment 'out of spec number' on torque allocation referencing 885140, but
no data yet.
NEXT ACTION: Phil gives his data, Dave answers his "quiz". The rest of the
list, runs to get 885140...