2001 C70 T5 Coupe low boost issues

perkunas · Post by **perkunas** » 10 Nov 2015, 11:20

An update on the car.
Strange sound under full acceleration. Mostly during long 3rd, 4th gear pulls, but can be present when pulling in 2nd gear (especially just after taking a turn, in my daily commute).

Sounds somewhat like wastegate flutter (i.e. but I'm not too sure, as the pulses are not as frequent. Another idea is engine touching the firewall under torque due to old engine mounts (top mount). I assume dying turbo is an option as well but last time I checked the compressor had no play.

I'll try to record it when I can, but maybe you guys have some ideas.

perkunas · Post by **perkunas** » 01 Nov 2016, 00:17

Problem solved by adjusting the wastegate preload a couple of turns. Turns out it was opening almost immediately when any pressure was applied (the wastegate arm could actually be moved a little bit by hand).
I'm assuming as there was little to no preload on the wastegate arm, the valve inside the turbo would get thrown around by exhaust gas, causing the fluttering sound and I would not be able to build boost. However, if the boost builded slowly, the valve would stay closed due to backpressure inside the turbo until the TCV decided to open it.
Now I just need to get a good pressure gauge to set it at 4.4psi, right now I am probably somewhere around 2-3 psi (using a cheap chinese boost gauge which is nowhere near accurate)