Saab 900 adjusting base boost on the turbo waste gate 

Yes its called age and wear 😉. Most cars have places to adjust for these things as they age. This car is also modified with much bigger IC, modified APC. There is a rod to adjust for a reason or else there would just be a rod with no adjust points at all. The repair handbook says that is the way to do it so i follow that. Right or not it works.

@@saab900turbo9 It did not work on my 9-3 T5 t25, I lowered the boost at both base and max boost, because the gate was not closed 100% anymore when adjusting the rod longer then stock. Had to replace the actuator to get a correct base boost, because the old one could no longer travel far enough to fully close and fully open anymore. The adjustment is there because the actuator is a universal part that fits multiple turboes.

​@@larsjrgensen5975 Then yours was obviously faulty or broken . It worked on this. The turbos might be different. On this one the shorter the rod the more boost and longer rod less boost. If i could not reach desired boost level i also would have changed this, but now i did. Well the instruction book says its there for adjustment. And i would be quite surprised if it did not need any adjustment after 33+ years. My base boost is now correct. I think the adjustable rod has multiple purposes. The ACP on this car works against base boost. I have modified it so if the base boost is 0.45 the max boost is 1.0 bar(0,7 standard). It was 0,6 so the full boost was close to 1,2 but seemed to try to climb more before the knock sensor stepped in and pulled it down to safer levels. I have also told it to keep the boost longer, at high revs the boost can drop very low on most cars. This tries too keep it as high as possible even at high revs.

@@saab900turbo9 As for as I know 0.15 bar higher base boost does not change the max boost to 0.2 bar higher, because the base boost is still lower then max boost, so the wastegate should have no problem adjusting the max boost down to the level the ECU is programmed to run at, if it works correctly. You are mentioning 33+ years, is the wastegate actuator 33 years old? if yes then I think yours is worth replacing too. If the APC system is able to boost higher then 1.2 and to a level where the engine starts knocking, but then lower the boost to safer levels then the APC system works, if you prevent this from happening with hardware you are sabotaging the system from working correctly. You should program the ECU to get the lower boost level instead of adjusting the wastegate.

​@@larsjrgensen5975 The base boost is supposed to be 0.45 and the APC(ECU has nothing to do with the turbo on this old car)use this to calculate max boost. How to "program" it is that you open up the box and solder it and turn some knobs. Its like all computers that base all their speeds on the Ring bus/infinity fabric former known as front side bus. It looks at the bus and the ads a multiplier on it and then you have the speed for example on the cpu. before unlocked multipliers(like i tuned my box) you tweaked the FSB for more speed. Example: bus 100mhz, cpu speed is bus *15 = 1500mhz. if you could not go beyond 15 you could instead tweek the bus: bus 125mhz *15 = 1875mhz cpu speed. however it could ad a host on problems because everything in the computer calculate the speed with this bus. I think this system behaves very similar, i looks at base speed and ads a multiplier or just 0.x bar boost to that. If the base boost is 0.1 bar or 5 bar i does not care. Mine still works as intended so no need to replace it yet, maybe for the looks of it because its all rusted.