I've seen some cases here on the forums of others showing large amounts of carbon deposites with as little as 20k miles on the engine. I assume those with harder miles have more build-up.
At 83k miles
, to say my valve cleaning was overdue would be an understatement.
Personally, I think cleaning the valves on the N54/N55 engine should be a regular maintenance job every 50k miles (at the least). It really is unbeleivable how much carbon gets caked onto these valves in little time. The degradation of performance is equally surprising. BMW seems to be pretty silent about the issue.
IMO, the only practical method to cleaning the valves is walnut shell blasting, which can be anywhere from $400-$1000 to get it done (dealers are obviously more $ - this is not an easy DIY procedure to shop around). Some have manually scrubbed the carbon off, and then 8hrs later they collapsed from inhaling the chemicals and scrubbing all day. I made that up, but seriously, this shit does not come off easy. Just pay a shop and get it over with.. you'll thank me later.
On that note, thanks to UltimateBimmerService
in Dallas. Brent and Ryan are classy guys and very professional; it felt like they were treating my car as if it were they're own.
After looking at these pictures and seeing what the shop removed, I completely understand why my car no longer feels like I'm pulling a Boat behind me. That's no exagerration. The car feels amazing now! It sounds like it's breathing better as I can hear the turbos and never could before, and the rasp at the top of the powerband is so much more pronounced.
The workmanship and level of detail are better explained in the photos - what a difference!
They also resurfaced the deck for the new Intake gasket. Top notch.