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Re: boost increase[240-260/1981] posted by JohnB on
Tuesday, 7 April 1998, at 1:15 p.m.
This 'rod' is on the turbocharger if you have an integral wastegate.
Some cars have boost popoff valves separate from turbocharger...these can be adjusted by loosening the locknut and turning the screw...or disassembling the popoff regulator and shimming the spring with washers.
The rod has a locknut on it..make sure the rod to the diaphram is held stationary when you try to unlock the nut...if you turn the rod to the diaphragm you will ruin the diaphragm and have no boost...wastegate has nothing to hold it shut. Once rod is unlocked, disconnect the rod from the wastegate (pull clip, unhook rod) and lengthen rod by roughly 3 turns per psi....check max boost with a calibrated pressure gage (I bought a relatively inexpensive one from GM used on Buick Grand Nationals...it goes to 30 psi...hmmmm) and don't exceed 13-14 psi...the overpressure switch is supposed to cut in at 15 psi. You MUST use premium gas...no telling what will happen at high boost levels with regular gas if the knock sensor doesn't cut back timing enough....Saabs control boost AND timing retard, but the volvo system I think just retards.
The saab apc system can be fitted to volvos...it works quite well by bleeding off the pressure to the wastegate diaphragm...see the turbobricks board for details...under conditions that the engine can stand it. Very similar to the Volvo Turbo+ setup but considerably cheaper if you can find a junked 900t.