re. boost limit fuel pump cutout

Ben Swann benswann at
Fri Aug 3 03:45:09 EDT 2007

Don't waste too much time and effort on hacking the ECU and other means of
over-riding safety features.  I have a chipset for the 200 that is reasonably
priced and works without any safety issues.  See:


There is a complete writeup I did several years back that tell how to hack the
ECU: but really a decent chip is a
better way to go.  The pressure regulator mod is a good way to go if you want
to get even more boost than with just a spring and has been used to push boost
levels to even above the limits of adequate CIS fuel delivery - be careful!




[Date: Thu, 02 Aug 2007 05:57:47 +0000

From: ckrug7380 at

Subject: boost limit fuel pump cutout

To: quattro at


I have an '89 200TQ (my second), and I've been contemplating cranking up the
boost a little.  I remember researching this before, and there's a
modification to the ECU to disable to fuel pump cutoff at 1.4 bar.   But, I
had an idea.  Since the ECU gets it's boost information from a dedicated boost
hose, wouldn't it be possible to cut that line, and install the following two
items in parallel in that line?   First, a pressure regulator set at just
below 1.4 bar. This would ensure that when the boost goes above there, the ECU
only sees a "normal" reading.  The second item would be one of those nifty
little boost valves that Rick Gillis makes (  Set it to
what you want your maximum boost to be, for example, 1.7.  If something should
go wrong and the boost exceeds 1.7, the boost valve would open, bypassing the
regulator, sending full boost to the ECU, killing the fuel pump ground.  I
think it will work, unless I'm missing something.  

With this system, the ECU should retain a correct boost signal except under
WOT, and you still have the failsafe of the fuel pump kill.   Anyone have an
upgrade wastegate spring they don't need anymore?  Oh, that reminds me, on
that wastegate actuation... does the boost pressure sent to the actuator pull
the gate open, against spring pressure, or assist the spring in keeping it
closed?  It makes a difference in how I proceed.  Thanks


Calvin K.


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