So something that Nevyn72 touched on earlier in regards to the metal throttle elbow requiring the hose for the boost controller to be plumbed elsewhere.
I had tapped it into the return line from the BOV to the manifold. (I kinda didn't have any choice at the time)
As I have since learn't, this is not the best way to do this.
The first thing I noticed after the exhaust had gone on is that I could actually hear the BOV, but not at full throttle gear changes, only mid rev range changes. I thought maybe it was just the engine noise at high revs, but it defiantly was much much louder if I was cruising at half throttle and then changed gear. Also the turbo whine was considerably louder at part throttle!
The other thing I noticed was the boost was a bit erratic. It would build boost as normal but then when it hit 8psi in the higher rev range at full throttle, it would drop to 6, rise to 7 drop to 6psi etc before I then changed gear.
It definitely was not like this before the elbow upgrade.
So this is what was happening:
At half throttle cruising up a hill I was hitting full boost as you would expect. But for the boost controller to see full boost behind a half closed throttle body the turbo has had to spin up significantly higher pressure. I don't know how high, would have loved to measure it with a gauge at the turbo, but lets say the turbo is making 15psi before the controller sees the factory 7.5psi.
Imagine a steeper hill and only using 1/4 throttle to putt away at a constant speed up it. The turbo would be pushing 30odd psi for the controller to see 7.5psi behind the almost closed throttle body.
Close the throttle and WHOOOOSHHHHHH goes the BOV!!!
The negative of this is excessive heat from the turbo spinning way out of its efficiency range , the wastegate would be seeing vacuum which apparently is very bad, and im guessing possibility to pop a hose off at extreme pressures.
So the solution:
I got onto NitroDann (who is about 15 minutes drive from my house! Awesome
) and he welded on a barb outlet on the metal elbow where it was located on the factory rubber elbow.
First of all I have to say, I'm genuinely impressed with the quality of work by Dann.
It was only a small little job but look at the welds! Now look at the temp sensor weld that was already on the elbow for comparison! Eww.
So after I re-installed the elbow, I didn't realise that the factory hose coming from the boost controller is 5mm internal and the new barb was the standard/normal 2mm I.D
I had some 2mm vacuum hose left over but no step up joiners, and none of the local auto shops seem to sell such a thing
So this is a bit getto, but I managed to fit about an inch of the 2mm I.D hose inside the 5mm I.D which fit very tightly onto the barb
Its held down with a screw clamp and doesn't show any signs of leaking and survived the pull test, so will do for now till I can get a step up joiner.
The result: Instantly noticed that at full throttle the boost climbed to 8psi and stayed there right till redline.
Cruising up the hill near my place at half throttle the turbo doesn't whine anywhere near as much.
Also the BOV is almost inaudible in the same situation (boo didnt want that
I liked the sound)
So yeah, If your upgrading your rubber elbow to the metal one, get an outlet welded on before you install to avoid dramas down the track ;)