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Re: toasting an O2 sensor, hesitation at boost, and more

> It was found by an independent researcher that the code in the 200q20v
> Hoppen, (earlier) Intended Acceleration, and TAP chips were functionally
> identical, with no significant variance in the code.  However, the code is
> designed to operate with a 2.5 bar pressure transducer (PT), as the code is
> set up to allow 2.2 bar. A 2.0 can't do 2.2.

Actually, they usually can.  What happens is that they deliver a
(correct) voltage out of the range expected by the ECU, so the ECU
'sees' overboost and shuts down the fuel pump.  The _real_ 'el cheapos'
just put a simple voltage divider circuit between the PT and the ECU to
fool the ECU into thinking boost is lower than it is, and shove in a big
spring or Schrapnelknobbeln.  Chief symptom? The dashboard boost gauge
is either disconnected or the owner is told to mentally remap its
output: "Yeah, it's only saying 1.3 bar but it means 1.8".  A second
kludge of some sort is then required to increase fuel flow - cheapest is
a different profile in the metering head cone or a tweak to control or
system pressure.  The cost of doing something like this is about $60 -
I've seen people pay over $1000 for it.  The ECU _isn't_ remapped.  Easy
to check - pull the ECU apart and look for the chip.  If there are any
extra wires soldered around the pressure sensor area, beware.

These cars often have very strange fueling problems.

I've never seen any of Ned's workmanship, so I can't comment.  I've been
told it's very good. I know that ECUs modified by Scott are
indistinguishable from stock, except for the fact that the EPROM sits in
a socket rather than directly on the board.  But even a low-power
microscope (a dime fills the field of view on my binocular workshop
microscope) shows the reverse of the board as neat as an original
Hitachi board.  And for those intimately familiar with Hitachi's
industrial production standards, this is indeed an achievement.

> The stock 91 200q ECU has a 2.0 bar PT, as opposed to the 2.5 bar unit that
> comes stock in the AAN motor in the UrS4. In order for the code to be
> maximized, the 200q20v ECU must be equipped with the 2.5 par PT. TAP was
> apparently unaware of this (per the independent researcher's conversations
> with them), and was thus reportedly realizing 265 HP with that code. The TAP
> code, when coupled with the 2.5 bar PT, delivers around 277 HP, safely. Your
> ECU has the upgraded 2.5 PT, and so is able to realize 277 HP.

Yes.  There is also a very scarce 3 bar sensor.

 Phil Payne
 UK Audi quattro Owners Club
 Phone +44 7785 302803  Fax +44 870 0883933