Adjusting Base Boost on GM900 2.0 turbo's. [Archive] - SaabCentral Forums

: Adjusting Base Boost on GM900 2.0 turbo's.

1st September 2002, 08:15 AM
Hello all.

Has anyone Measured and made adjustments to their base boost Setting as Per the instruction on this web site at the following link?

I would Like to know what Kind of Boost Levels people found before making the Adjustment.

Was your boost Lower than Max?
was it higher?
Did performance increase once adjusted?

And So on... :roll:


2nd September 2002, 02:53 PM
We don't have APC in our cars.

7th September 2002, 06:10 AM
Talk to me huston...we have a problem!!


7th September 2002, 04:59 PM
APC is automatic performance control, which is the boost control system on C900's...turbo GM900's use the Trionic 5 (T5).

The link you posted referred to C900's.

8th September 2002, 08:14 AM
Thanks for the info Conrad.

Any reason why on my Turbo Meter it Says APC?

Are you saying my GM900 uses the T5 type of APC?

Have you any idea what would happen if I adjusted Base Boost?

P.S. I have turned the WasteGate Rod 1 turn and found a small incease in power, now the Turbo Gauge seems to peak over into the red a bit.

Should I change it back? :-?

Any advice recommended,

10th September 2002, 01:29 PM
Hey Bernie,

Couldn't tell you why your turbo gauge says APC. I'm venturing the guess that it is still a form of "automatic performance control." My 9-3 just says "turbo".

Yes, your car has the T5. really an ingenius system that controls boost pressure, timing, and fueling on a cylinder by cylinder basis. it uses the spark plug to measure fuel ionization in each cyl.

Turning the wastegate rod will increase base boost, as you mentioned. I have heard other ppl turning their GM900 wastegates one turn without ill effect. Just don't turn it too much (ie it'll start to knock and not be able to reduce boost enough to get it to stop because your wastegate won't open far enough)


11th September 2002, 05:24 AM
All Saab turbos use APC in one form or another. Back in the days when they used Bosch fuel injection, APC was taken care of by a separate box. Nowadays it has all been integrated in to one box, the Trionic. However the functionality still remains, hence the APC designation on the gauge.

Basically APC aims to get the maximum performance out of the system whilst keeping it safe. It moderates boost presssure, fuelling and timing to help cater for differentials in fuel, temperature and atmosperic pressure, all of which can have a big effect on turbos.

They build in fairly generous safety margins, meaning that for an un-modded car, you will notice little difference in the perfromance from day to day.

18th November 2002, 06:15 AM
Well Ive just put my Abbott MBC on and what a difference.
Power comes a lot quicker and holds the boost to around 1 bar(is this still safe, Abbott said around1.1bar is ok).It is just sitting in the red on the gauge.
Does the ecu give the engine more fuel for the extra boost?

Any advice recieved