Maximum torque for the na I5 engine.

[Orin Eman]

> 
> > > Can you detune the engine to meet the power and torque limits?
> >
> > I am working on it, the problem is to find a trusted dyno facility that
> can
> > do the measurement. To detune the engine will not be a problem, a retarded
> > ignition map and low boost pressure will do the trick. The inspection guys
> > would find a throttle limiter in a few minutes.
> 
> I am not yet 100% clear on the true effect of the wastegate spring.  I think
> a softer spring might do something in the right direction.  Not sure if it
> needs to be paired with distorted pressure information.  As I understand it,
> the spring is what sets the upper boost.  The control the ECU has is to help

The spring sets minimum boost.

> the spring open via vacuum on the top of the wastegate as it detects the
> boost going up in order to avoid overboost due to inherent hystereses in the
> control system, and to feather the abruptness of the springs opening.  Some
> systems have an ability to control the spring in the other direction, too,
> by pulling on the wastegate diaphragm from "below" with vacuum, adding to
> the spring's pressure.

Actually, on the MC and similar, the ECU controls boost by switching
the upper wastegate chamber from just before the turbo (_slight_ vacuum)
and manifold pressure (boost pressure).  The default state is switched
to just before the turbo giving a default boost of slightly less
than that given by the spring alone.  When the ECU wants to increase boost,
it switches the upper wastegate chamber back and forth between slight vacuum
and boost.  This increases pressure in the upper chamber and aids the
spring, holding the wastegate closed longer.  The amount of extra boost
this creates depends on the duty cycle of the wastegate frequency valve
which does this switching.  You can get 1.8 bar just by reprogramming the
ECU to use higher duty cycles, but it is _slow_ to get there.
You can't however, program a reduction in boost below what you would
get by unplugging the wastegate frequency valve.  In general, it seems
that the difference between leaving the upper wastegate chamber open and
applying the slight vacuum from before the turbo is about 0.1 bar.

Orin.