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

[Sargent Schutt <Sargent@SymposiaFoundation.org>]

Brett,

My memory is not perfectly specific, but roughly, the details are as
follows: (You can find this thread from the archives of the 200q20v list
late 98 to early 99.)

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.

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.

To wit: the 2.5 bar PT is now offered as an option at TAP.

on 11/29/99 11:41 AM, Brett Dikeman at brett@pdikeman.ne.mediaone.net wrote:

> At 10:26 AM -0800 11/29/99, Sargent Schutt wrote:
>> Brett,
>> 
>> Just an FYI, the chip should give you 277 HP, not 265.
> 
> Hmm.  TAP disagrees; they told me that it would be "somewhere around
> 265" without the spring, and "285" with the spring.  Oh well.  I
> always thought the tuners pull the figures out of their rears :)
> 
> 
>> The TAP code is
>> reportedly functionally identical to the Hoppen and IA units of the time,
>> both of which give 277 HP. The spring is basically useless in the 20V. Just
>> know you have a 277 HP chip, unless you changed it from what I sold you. It
>> will provide 2.2 bar of boost (has 2.5 PT) and reports 1.8 as a conversion
>> (gauge is a relative reading based on a signal from what it thinks is the
>> 2.0 PT)
> 
> Right, this is what I thought...so I shouldn't be seeing 1.5 and 1.6.
> Hmm.  That means that something is quite wrong. The $5,000 question
> is...what?

You should see 1.7-1.8 on the gauge = ~2.2 actual. Pull codes? Vac leak or
line pinch? Any stalling problems or low idle/idle dip/rough idle issues?
Problems at idle can be borne out with lower boost capability. Bad gas
(knock sensors kicking in). Check turbo spindle: play in it? Smoke on
startup? Michelin man hose going south? IC leaks? Lower IC hose? All clamps
tight? Hook a shop vac up to the hose exiting the turbo cool side (duct
tape), plug the intake track at the throttle body (disconnect) and look for
leaks.

> 
>> . Note, the dash gauge is not the most accurate gauge in the world,
>> either.
> 
> It's perfectly -accurate- since it is derived directly from the
> pressure sensor the ECU uses.  However, the -precision- is very low
> and there is a slow refres rate, plus it is unknown whether the
> ECU/board computer rounds or truncates the measured boost value.

Semantics: the issue is boost level. If it isn't precise it isn't accurate
either. That's the problem.  Replace the dash volt gauge with a VDO boost
gauge. You can get a matching one (red backlit) in matching size. A little
dremel work and some wiring/plumbing and you have a dash gauge. Move the
volt gauge to the ashtray. Take the quarters to the bank.

HTH. She should be very fast, if you've got everything squared away.

Regards,

Sarge