4kq V8

[Phil Payne]

> So, how bout those torsens, eh?  Think they're any good?

Heh.

I've just been investigating a 20V ur-quattro with a cracked subframe - and I think the Torsen
may be partly to blame.

Check out an ur-quattro rear subframe, left hand side, underneath, where the forward-facing
arm connects with the transverse section.  The two halves of the subframe are (heavily)
spot-welded together, but the inside of the lower half has a hole with a quite small web to
the weld.

This is where it cracks.  But only on 20Vs.

I strongly suspect this is the result of a combination of factors:

a) The low-end torque of the 20V - 309 Nm at 1950 rpm.

b) The speed with which the Torsen can switch the torque from one axle to the other.

I hypothesise that a sudden front wheel slip on a heavily-accelerating 20V places two sudden
strains on the subframe - first the subframe carries the differential and the halfshaft torque
has to be resisted, and second the straightforward applied torque from the propshaft.  This
can go from 50% of engine output to 80% of engine output in a heartbeat.

--
  Phil Payne
  http://www.isham-research.com
  +44 7785 302 803