I've read on this forum and another that there is supposed to be a small restrictor in-line on the hose that runs from the turbo outlet to the T fitting. Is this true? Is this on '03 WRX's? I've also read that if a car is missing this restrictor, it won't build full boost... Well, I have an '03 WRX Automatic, and there is no restrictor in the hose...

also, on a sort of related note, does anyone know how the Cruise Control works on an Automatic WRX? When I set mine to 75mph, it keeps the revs at a constant 3000 rpm. Doesn't matter if I'm going up a slight grade or down a slight grade, RPM's stay constant, and I can hear my wastegate and BOV doing their thing as I go up or down hill. Just curious if speed is controlled by boost vs. RPM on this car.

 

The RPMs stay in the same range because you're shifting gears... that's why the BOV is going off. I do highly doubt the needle says pinned at or near 3000 when its shifting

jason

 

i'd like to point out that there are two things that restrict airflow in the FBC system.

the first is, as mentioned, an externally visible plastic coupler. iirc, this is between the plastic T and the FBC solenoid near the passenger's strut tower. this can be replaced with a larger coupler which allows the FBC solenoid to bleed off air more easily, thus raising boost. this is the famed "3/16ths" mod.

the second restrictor is actually invisible, and is located inside of the short section of tubing connected directly to the turbo's compressor housing nipple. you can only check for the existence of this restrictor by squeezing the hose with your fingers. do it while the engine is cold! it's a small piece of brass with a tiny orifice in it.

if you remove THIS restrictor you will never get more than wastegate boost. this restrictor is there because the FBC solenoid cannot bleed enough air to cause the requisite pressure drop in the connection between compressor and wastegate acutator to raise boost over 8psi without it.

hth
ken

 

Thanks guys. I have done the "3/16" mod, and wow, that's an improvement. The little brass restrictor is the one i was referring to... I'll check my hose in a few hours when the motor cools down.