Turbo Talk... & HKS Controllers

[Peter Dufault]

>       ... The system will monitor the engine for
> 	knock and if your running good gas and have boost with no knock
> 	then the system will let you boost even more untill you 
> 	start to knock and then will slowly drop the boost untill
> 	knock is low and the it will start to increase the boost again
> 	untill it starts to knock.. 

If memory serves re: an '86 system we used to have, the
APC unit is a completely separate add-on with its own controller
and wire harness appropriate for DIY.  There is a knock sensor and
a solenoid that opens a turbo bypass valve that routes some of the
air coming out of the compressor side of the turbo back upstream
of the intercooler.  The solenoid is simply open-close with no in
between settings. So there are two boost settings - the upper
setting limited by the wastegate setting with the bypass closed
and the lower setting set by system geometry when the bypass valve
is open.  I think that in that early unit the APC control just
opens the bypass valve when it detects knock and then closes it
again after a delay.  It was effective.  Given the price of old
900Ts you should be able to get the pieces cheaply.  I could be
wrong about some of this but I'm pretty sure that is the way that
system worked.  Newer integrated systems monkey with timing etc.

Peter

-- 
Peter Dufault (dufault at hda.com)   Realtime Machine Control and Simulation
HD Associates, Inc.               Voice: 508 433 6936