Unusual problem with LH 2.2 system

John Bertram bertram at teleport.com
Mon Jun 23 05:56:51 GMT 1997


>Now a few questions for John Bertram.  Did you install the Saab APC knock
sensitive boost pressure control system yourself? 

Yes, the complete details of the installation can be found at:
http://www.teleport.com/~bertram/volvoapc

>Are the LH 2.2 system and the EZK 117 system OEM components?

Yes, these are the factory equipment.

>OEM systems can run very rich at wide open throttle (WOT) for a number of
>reasons (I am assuming that 12-14 psi of boost is WOT?) including catalyst
>temperature control, exhaust valve durability, or possibly knock control.

The LH 2.2 system works with the EZK 117 and has a knock sensor.  The
Ignition system retards the ignition 3 degrees per cylinder that is
knocking.  It also sends a signal to the LH 2.2 when knock is detected and
the LH then richens the fuel mixture.   

>Possibly your base fuel surface is wrong since it sounds like you have
made >some hardware changes to the engine.  If it is possible to drive
steady >state in the condition that is causing the black smoke you can
easily find >out.

It is easy enough to reproduce the smoke situation.  Not for a long period
of time though.  It only does it while decelerating from high boost to
lower boost.

>Also, when you lift off completely you are probably going into decel fuel
>shutoff (DFSO) and thus no black smoke.

I'll have to check into this.  I am not sure if LH 2.2 shuts down the
injectors on deceleration.

>FYI on O2 sensors.  The frequency of most systems for feedback control of
the fuel/air mixture is around 2-3Hz on the high side.   There isn't anyone
who knows the answers on catalysts (or if they are they aren't sharing it
with anyone I've worked with) so closed loop fueling is full of opinions
and question marks.


John Bertram, Technician
Garry Small Saab
(Turbobricks list Admin.)
Volvo Turbo APC project (www.teleport.com/~bertram/volvoapc)
'87 Volvo 740 Turbo Sedan
'70 Toyota Corona Mk.I



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