Gtr Actuator Not Opening Until High Boost

[kristafa]

car is fitted with stock turbos/actuators, rear one opens with minimal air pressure (as tested with air compressor and regulator), the front one however requires like 20psi before opening, then i can actually open and close it quite freely until it fully closes again.

to me seems like something inside the actuator is binding before allowing it to open fully. If i assist the movement of the wastegate arm, again it comes out easily. There is no air hissing from inside it, so the diaphragm seems to seal just fine.

I dont know really what they look like inside, but i can't think what it might be binding on. any suggestions? I haven't used these turbos before, so its possible that the wastegate housing was deformed in transit, the vac nipple on one of them was bent over a bit, could have been this one possibly, but unsure.

If the wastegate housing is slightly deformed, would this cause the issue (ie the internal "piston" or whatever is there is catching on the inner wall of the housing, until being freed by more backpressure)

the actuator housing doesn't APPEAR deformed but if i can't find a solution, i'll take it out for closer inspection, but that will be a c-word of a job, not much space in this bmw engine bay.

thanks all

chris.

[GTRNUR]

You need to remove the circlip from the actuator arm and test the movement of the actuators without them pushing on the arm.

If they dont operate identically then you should replace them both so they are matched.

[kristafa]

Yeh cheers. The test was done with the arms detached from the wastegate, seems i've fixed it tonight, the vac nipple on the actuator was likely damaged in the mail, i thought i bent it straight again but still was a bit misaligned, got it nice and straight with pliers and now the arm moves unrestricted and in unison with the other actuator.. Not sure why this would affect its operation, but seems to work well, again using the compressor and air reg, they both start to open from 5-7psi and fully open around 10 which i think sounds right..?

I love these cars!! Back to the dyno now.

christo.

[JonnoHR31]

they both start to open from 5-7psi and fully open around 10 which i think sounds right..?

yer thats right. the bend must have been restricting it enough to be a problem

[hypergear]

There is a rubber diaphragm in side those actuators. If the diaphragm leaks then it will not/hard to open by vacuum pressure. See if you can blow air through that actuator. If so it means its not good.

[kristafa]

Thanks stao, no noise comes from the actuator and it holds pressure.. Think its resolved now, thanks all.

[Duncan]

good choice to test them BTW....I tested some the other day, 1 opened at 12psi, the other at 15psi. ie one turbo would have spent it's life working 30% harder than the other. brand new actuators

[snozzle]

whats the best way to test actuators? what kind of tools do u actually use?

my actuators are adjustable so i may aswell test them out to see if the person who installed them did a good job

[Duncan]

I used a compressor, with a regulator keeping it under 20psi, and a bleed valve. T-piece for a boost guage. Set it to 5psi, link it to the actuator and slowly close the bleeder until the arm moves.

I understand the adjustable length of the actuator only adjusts the preload on the wastegate, should be 3-5mm. I guess that affects the boost by maybe 2psi? But I don't see how it can be really "adjustable" far from the preset tension of the diaghram

[SiR_RB]

just found out i got adjustable wastegate actuators on my -7's

with my profec off tthey boost to about 9ish psi so most likely set to 7psi

how do you go about them holding higher boost? tighten the arm thus making it shorter? or lenghten the arm by loosening the bolt?

il do the compressor/air reg test to see how they perform aswell

[DVS JEZ]

Tighten them = more preload.