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