Timmerman "Shrapnnel-Knobben" mod et. al.

Robert Myers rmyers at oak.total-web.net
Wed Oct 18 13:17:56 EDT 2000

At 10:23 AM 10/18/00, urquattro wrote:

> > This is great info.  Taking the leap into territory that I am only a bit
> > familiar with has anyone done or looked into wiring a potentiometer in
> > place of the resistor so that you could adjust the timing/fuel pump shut
> > off point as the situation requires....
> > Any thoughts or BTDT?
> >
> > >>To keep the fuel pump cutout from kicking in, you need to modify the
> > >either by chip, or some less elegant way, eg. the resistor mod.


> > >
>... Paul's mod to the ECU was a resistor/zener mod, not simply a resistor.

Correction!  Paul's mod was a resistor bridge based upon the Wheatstone 
Bridge.  The zener/resistor mod accomplishes much the same thing but that 
isn't what Paul did.  In addition to the bridge circuit he also provided a 
pressure regulator to permit addition of regulated boost pressure on the 
top side of the WG diaphragm.  This reduces the pressure differential 
across the diaphragm thus extending its life.

>The zener clamps the input to the A/D so that the ECU never thinks it sees a
>pressure above that point and thus does not activate the overboost shutdown
>mechanism.  Many people swear by this mod, claiming many miles of trouble
>free service, but personally I would not recommend doing it.  As long as all
>is well it may be fine, but be sure to keep all of the car in tip top shape
>at all times, because if you get something like a tear in the WG diaphragm
>things may change in a hurry.


>I would also like to speak against the thought of putting some sort of an
>adjustable voltage divider in the boost signal to the A/D on the ECU.  The
>whole reason the ECU is there is to take inputs on manifold pressure, engine
>RPM and throttle position and determine the operating parameters of the
>engine ... ignition timing, WGFV position, and yes if the fuel pump should
>be shut off.  By scaling the voltage you are causing the ECU to think that
>the engine is running at a different point in the maps than it really is.
>This may not be that bad a thing, but it is not likely that the timing
>parameters will be better at this operating point than they would have been
>if the engine really knew where it was operating.  Realize that I don't have
>a problem with scaling the voltage out of the pressure transducer to
>increase the active range available to the ECU, but if it is done, the code
>in the ECU should have a commensurate change so that it "understands" the
>new calibration.
>To anyone who wants to gain an understanding of what is going on inside the
>ECU I heartily recommend checking out Robert Houk's site:
>     http://www.tiac.net/users/rdh/http/Urq/
>While his work is focused on the ECU of the urquattro, most all of the
>subsequent 10v turbos have a control system that is very similar ...
>Steve Buchholz
>San Jose, CA (USA)
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  Robert L. Myers  rmyers at oak.total-web.net     Home 304-574-2372
  Rt. 4, Box 57,  Fayetteville, WV 25840 USA   WV tag Q SHIP
  '95 urS6  Cashmere Grey - der Wunderwagen    ICQ 22170244
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