Re: RE: Toasting an O2 sensor, hesitation at boost, and more

[Orin Eman <orin@wolfenet.com>]

> Jouko writes:
> >My '88 MB Urquattro MTM ECU has a modified fuel-ign map chip and a
> >resistance on the output of the pressure sensor, along with a significantly
> >stiffer spring.  I run around 1.8 to 1.85 bar with no detonation, will try a
> >little more boost in the spring.

> I'm not familiar with the MB ECU specifically, however, when I hear of 
> resistors modifications on a 2.0bar PT with a car under 2.0 maximum boost, 
> chances are the overboost cutoff hasn't been changed in the chip, nor have 
> the WGFV values, both values are just being 'fooled' (computer thinks it has 
> a percentage of actual boost voltage value).  The above would be the 
> equivelent of an early Stage II Mac-11 modification with revised 
> fuel/ignition tables only (or really more similar to a MAC-02 without WGFV 
> operation).  My own thinking is that if your spring is really stiff, the WGFV 
> probably is operating less than you think (if at all).  A chip that has 
> properly addressed the WGFV tables, should be able to go higher than stock 
> boost levels with a totally stock spring.

This is true.  I've done it.  1.8 bar with a stock spring.
BUT... it's slow getting there.  Putting in a stiffer spring
allows boost to build up a lot faster.  I run a 1.8 bar ECU
with a 1.6 bar spring.  The combination works well IMO.

Orin.