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When I talk about max boost, I'm referring to the cut off point built into the ECU...On stock 850Turbos, this max boost pressure was approx 10.3 psi. On the R and T5R this was about a pound higher . On my IPD ECU, the program raises the cutoff to 13.3 psi, and on the IPD ECUs for the S70Ts, its around 14 psi. Obviously, the higher the program for max boost pressure allowed, the greater the adjustment you can make to the Actuator rod before an overboost condition sets in. But even with the stock ECU, a certain amount of adjustment is permitted, so long as you dont exceed this max boost level, at which point , as you accurately point out, fuel and boost are cut off. I've never reached this point, and never logged a fault, despite the adjustment. Others who have 'gone too far' with this adjustment have experienced this condition, however.
There seems to be some variation as to how this setting comes from teh factory. According to my Volvo literature, there is supposed to be 1.8 psi +/- .145 factory setting. This is the pressure you're supposed to pump into the servo when setting the actuator arm adjustment. However, in my case, there was zero tension on the acuator. From what others have reported on this forum, similar variations in factory adjustment can be found. Therefore, while I can report that my 4.5 turns works perfectly in my case, in another case where the factory has set this adjustment differently, such an adjustment may be too much.
Lastly, when I talk about driving with the needle in the black part of the gauge most of the time, this was to draw attention to the fact that if the adjustment is made so the arm is too short, you will find yourself almost constantly in the boost, as pressure will not be allowed to bleed off as required. Needless to say, among other things, gas mileage will shrink to nothing.
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