Hi group. I have been helping a friend get his turbo sorted after many unsuccessful trips to a local BMW specialist. The car has had so many things done to it, it feels a bit like a big nest of cabling that we are slowly un tangling.
The car is part of a collection of that has a few turbos so I have the luxury of being able to drive cars back to back to compare. This particular car didn't seem to be making boost despite having a new Kuglefischer (rebuilt) and Turbo installed (nos). The car runs like a NA car at then at 5500 it sort of hits a wall and slowly climbs through. Because of the "new" turbo we decided to go through a number of key settings and make sure to reset / baseline before going forward.
140, 140, 142, 140 (4-1)
25 degrees max
Pertronix in distributor and Pertronix Coil
Swapped with a known good unit timed the same (no change)
The rebuilt pump was installed and because they didn't know how to setup the pump correctly, they used the verbotten screw to richen the pump up to attain a stable idle (no threads showing). Linkage rods, throttle cam and pump we all set incorrectly and as a result the car was running very rich. AFR was low 8's and high 7's at WOT.
289mm rod was measured at 276 - throttle butterfly was not opening correctly. This has been corrected.
Reset this all and now the WOT setting (logged) maxes out at 11.6 and stays in the 11.8-12.5 range. I can share the log. Curiously at the 5500rpm wall there is a pronounced leaning step on the log of about 0.5 AFR.
Checked fuel pump pressure with a proper gauge, very stable at 28 psi at WOT as measured at the cold start injector.
Boost limiting valve:
Thought I found my issue, boost limiting valve on charge pipe was not opening and has a pronounced rattle (not a little rattle but a big rattle). Swapped with a known good unit that I could actuate with my hand and medium pressure. NO CHANGE......hmmmm. This is where I started to really start to think we have a legit boost issue. Maybe I took for granted that this car has a new turbo, I started to look at the manifold for cracks, gaskets etc. Notice that the #1 gasket (head / manifold) is flipped (who does that?).
nothing visibly damaged, all clamps in place and tight.
So that is where I am at. I am prepping to pull the turbo manifold to correct the gasket and inspect the turbo, housing, manifold etc. Prior to that I was thinking of rigging a way to pressurize the cold side of the turbo to see if there are any major leaks.