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RE: More SuperChips stuff

> Date:      Sun, 04 Sep 1994 13:03:32 PDT
> From: "Dan Bocek" <dan@di.com>
> Organization: Digital Instruments, Santa Barbara, CA
> Reply-To: quattro@swiss.ans.net
> X-Charset: LATIN1
> X-Char-Esc: 29
> Tomas -
> > When I bought my chip upgrade I first de-soldered the original prom
> > and dumped it to a file, just to be able to restore the box. I
> > soldered a socket to the PCB and put the original prom back, hoping
> > that the guys that was doing the mod would be lazy enough to
> > appreciate that someone had already done the hard work.
> > 
> > Well, they were ;-)
> > 
> > When I got the box back, I also got the old prom back, I immediately
> > opened it up and pulled the prom and dumped this one also. Now I only
> > need the spring if I get another car with the same box.
> > 
> > I think this chip is developed in Sweden.
> What car was this for, and what was the company that did the upgrade?
> Did you compare the two PROM dumps - if so, were there any differences?
> -- 

The car is a '90 100 TQ. 165hp original, MC engine, cat converter. The
company is "Svensk Turbo Teknik" aka STT. Original boost 0.4 bar (1.4
ATA), current boost 1.0 bar (2.0 ATA) -> ~210-220hp.

They have a very good reputation with their bolt-on turbo kits for
Mercedes diesels. I think you wont even void the factory warranty with
these kits. They seem to be very knowledgeable.

I did a 'cmp -l' on the two files and they are definitely different. I
looked around in the box after other parts that were changed, but I
couldn't see anything that looked like it had been put there recently.

The torque curve seems to have changed. There is much more low rpm
torque. This has the annoying effect of confusing the cruise
control. It tends to over-react when going uphill.

The waste gate also pulses rapidly when releasing the pedal at medium
to high boosts.

Come to think of it, the valve regulating pressure on top of the WG
can both increase and decrease boost pressure. As the underside of the
WG is connected between the turbo and the throttle, you always have
between atmospheric and full boost pressure there. The top can through
the electric valve either be connected to atmospheric pressure between
the FI head and the turbo or to manifold vacuum/boost. If the top is
connected to the manifold while running at boost, the spring holds the
WG closed. If, on the other hand, you have a condition of high boost at
the throttle, and high vacuum in the manifold, which would be the case
when releasing the pedal at boost, the pressure difference between the
underside and the top would be greater than the closing force of the
spring and the WG would open.

I disassembled the prom for the '85 200 TQ I had a couple of years ago
trying to find the overboost protection but to no avail. I even had a
logic analyzer hooked up to the computer while running the engine, and
using a bike pump I could vary the "boost" pressure seen by the
computer, until it shut down the ignition.