Remember there are two sides. One is with the power on, the first
number. The other is coasting, the second number. The two are
independent. The number of clutches however, works the same for both.
More clutches, more lockup. The clutches are also not as significant as
the ramp angles.
Carroll Smith's book "Drive to Win" has an EXCELLENT chapter on the
EXACT differentials that were used in the GPL era cars.
It is very interesting to note that the most common GPL settings ARE NOT
the settings they used in the real world, in fact they are opposite.
Ricardo Nunnini offers an explanation for this on his truly really great
site.
So, 85/85 with one clutch represents the closest thing to an open diff,
and 30/30 with 5 clutches is closest to a spool.
A real world setup would be 45/85 with one clutch. Carroll Smith said
in his book that he sees no reason to ever have the coast side ramp
angle lower (smaller) than 80.
Interestingly, Nunnini says the diff setup has perhaps the greatest
effect on handling on the cars in GPL. I noticed that when I replaced
the open diff in my 400+ hp road car, http://home.inreach.com/tjester/
with an Auburn Pro limited slip unit that it did make the car MUCH
harder to drive. After all my GPL experience, I now understand why and
wish that I had used a TorSen unit instead. The Auburn Pro unit is
probably better for drag racing, but I do very little drag racing.
Living in the mountains, most of my time is spent carving up the canyon
roads and I'd like a little less power on ramp angle ;-)
-Tony-
