Boost control

[einarp]

Jim,

The function you describe was called APC by Saab, and MABC by Maserati
back in 1985 or so. Not user programmable though, as the pot's were
inside the box.

This means you can get the solenoid from these sources. The parts used
by Maserati (including the control box) are made in Sweden, make your
own guesses here :-)

In the MABC the solenoid is pulse width modulated with a pulse frequency
of 14Hz. It's an analog box where Boost pressure signal, knock amplifier
output and RPM increase are taken into account.
It will lower boost if knock occurs, or preset boost pressure is exceeded.
During rapid acceleration it will allow more knock.

The parts used in it are cheap and readily available. On a DIY basis it
would be very cheap. The solenoid and pressure sensor will probably cost
more than the control box. If you are building an ignition controller,
put this functionality in there. That's what Weber did for Maserati
from 1988. It basically tries to avoid knock first by retarding ignition.
If that doesn't help, it turns down the boost. The signal level from the
knock sensor that will be interpreted as knock, is dependent on RPM and
defined in a table.
It also has a "rabid dog" mode that goes into effect if RPM rises fast.


--
einarp at ade.no  ( Maserati Biturbo Spyder )