ABS algorithms ...

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <933713F1FB7BD111AC2300A0C98F1AD1030E50@MILXPR06> "Buchholz, Steven" writes:

> I buried this question in a prior post on this, but since I didn't hear
> anything back ... when I opened the ABS controller that I pulled out of
> an '87 5kCSQ and compared the guts to the box from my '88 5kCSQW they
> appeared to be identical (the boxes had identical Bosch and Audi
> numbers) with the exception of two large DIP packages (~40 pin 0.6"cc).
> In each box the two parts were identical ... but differed from one box
> to the other.  The older box had chips in ceramic packages, while the
> '88 had plastic.  The thing that interested me was that the designations
> were similar, but almost appeared to be a revision change from the old
> box.  Does anyone know if there has been any refinement of the ABS
> algorithm along the way ... specifically in the 5k/200 quattros?

The major ABS change in the late 1980s was the introduction of the 
longitudinal accelerometer under the rear seat.  In the ur-quattro, this 
happened at the same time as the MB engine, TORSEN differential, orange dash 
and everything else turned up, in the 1988 model year.  This was a major 
revision of the ur-quattro - the WR version produced up to then was really 
starting to lag behind.  A fair bit of this technology reached the US market 
much earlier in the 1986 MC models.
 
I don't know when the accelerometer was added to the 5k/200 in the USA - but it 
might well have been right around then.   

(The Sport quattro always had an accelerometer connected to the ABS system, but 
 mounted to measure transverse acceleration.  One day I'll try and find out 
 why.)

-- 
 Phil Payne
 Committee Member, UK Audi [ur-]quattro Owners Club