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Discussion Starter · #1 ·
I just recently adjusted my base boost (screwing with the wastegate arm). I shortened the arm to get a good 10 psi. but when i put my foot in it, the boost guage reads 10psi for about 1 second, then it backs off to 5psi for no reason. Im guessing its the APC's fault?

Before i did that i disconnected the apc and got wild boost at half throttle.. but thats neither here nor there.

Anyway, my problem is my boost backs off. Any ideas?

Thanks.
 

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Blimey. Your base boost is set as such for a reason. Saab carefully designed it in this way so your engine didn't ingest itself. The reason your engine is backing off to 5psi is because the ECU sees boost beyond what it expected, and the APC acts to regulate it to a more sensible level. If you fiddle it so it holds 10psi, then the ECU will not be supplying enough fuel and you will end up with a selection of elaborate toilet roll holders where your pistons used to be. Don't do it unless you enjoy fitting engines of a weekend. There are safe and sensible tuning methods available, simply winding up the boost is not one of them.
 

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In principle the boost values your playing with is no problem for the car but you need to have an ECU map to work with it
With the map, it will control your higher boost, not your base boost setting
If you want to play with your boost, you can otherwise manually control it via a bleed valve restricting the APC vent or directly controlling the actuator supply & hence by passing the ECU control, this is the poor mans route & be warned your by passing some of your engine protection.
You will always have knock protection via ignition retard, but the ECU will not be able to knock back the boost & if you get a lean run you,ll be in trouble
But you can help to give it a wee bit more via the apc vent control valve
Not recommended to screw up your actuator rod because your also restricting the travel of the waistegate = possible boost creep at higher RPM & maybe a knackered turbo housing due to the heat this creates
 
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