This GM 3&4 turbo waste gate was not closing tight and it gave a DTC 78 . I would assume the ECM sensed it wasn't getting the regular boosthttp://www.dieselplace.com/forum/uploads/AZ2_turbo12.jpg.





I took it apart and flattend the pin the gate is stuck on. This seemed to take up the slack and enable the wg to close flat.


http://www.dieselplace.com/forum/uploads/D9D_turbo17.jpg


I didn't throw code 78 wg fault under hard acceleration. I want those of you who are running their stock wg turbo and switched to a mehanical spring arm to consider that if you are putting out a fuel rich exhaust plume you might have a waste gate that jams.http://www.dieselplace.com/forum/smileys/Geek.gif











Edited by: quantum mechanic

just out of curiosoty, could you measure the diameter of that flapper valve for me?

The orifice dimension is ~1.250" - does not take much distance between flap and orifice to dump boost.Edited by: gmctd

thanks, that's what I was looking for

I pulled a load today and it was my first chance to evaluate how everthing is working since the last round of work. The flow porting I did on the snail/wg housing, exhaust manifold and the turn down seem to have reduced the trucks exhaust volume (noise). During hard accelerations under load the roar of the engine seems to have been dampened by at least half.