Alpina B5s rattle after 'excess boost'?

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Alpina B5s rattle after 'excess boost'?

Post by kdw215 » Wed Dec 30, 2020 1:48 pm

I had a recent issue which has caused a possible problem. Car is a 2008 B5s with 63,000km.

Last week the charge pipe connection blew off at the lower intercooler pipe.
Car had a sudden loss of power, i pulled over 150m down the road with the engine barely running (had to continue to a safe point on the road). Luckily was only 300m to home.

Charge pipe was reconnected without issue, even if a few scrapped knuckles etc. Initially all good. But i now have a rattle/vibration/ slight knocking 'sound' at low load, 1000-3000rpm (i noticed it 2-3 days after). Goes away under full load and accelerating. But is there either hot or cold engine at low load 10-20% throttle. But does seem worse when hot. You can feel the vibration more than actually hear anything to be honest.

Had the oil and filter changed. No codes. Car has NO loss of power and otherwise seems 'normal'. But something has obviously changed.

I took off the engine covers, there is injector tick, and fuel rail is a bit noisy. But difficult to pinpoint any sound that 'matches' the feeling when driving. It's somewhat noticeable when revving stationary. It is in no way loud or can hear with the bonnet shut.

Does anybody have knowledge of the hot start mapping of vanos and valvetronic and what is normal? (i've read a plethora of posts on it, HVA and the like) I have noticed when engine is fully warmed up, on EVERY start 'warm up mode, throttled' is activated for approx 2 minutes, vanos has the cams at full duration (120°) and valve lift is at maximum (default) (9.85mm) then drop to 0.8mm lift and 80° duration on the intake side after the 2 minutes. I would have assumed if oil/water temps are at normal operating level then (0.8/ 80°) should be an instant change by the DME.
This could easily have been like this for a long time just never had the need to look at the data before and may just be a symptom of something else.

This maybe coincidental with the pipe blowing off.

Wondering if i could get any direction of what to ask the techs to look for or check.

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