Lets talk carbon buildup

[velodb]

I am fortunate to have some skills in turning a wrench here are there. Back in 2012 when my RS4 had 10,000 miles I got bored one weekend and yanked the manifold and was surprised how much carbon was on the valves and began cleaning and took my time and finished on a Sunday what I started on a Saturday. The car was starting to show some cold start misfires as logged via VAG not to the point of throwing a check engine light or storing a code but once the cleaning was done the cold start misfires as logged disappeared and shortly after I sold the car for other reasons.

Now as I enjoy the engineering, or should I say over engineering, on this S6 I marvel that if this pig gets carbon buildup, which I am sure it, the cure and necessity of pulling the intake manifold will require an engine removal to access the manifold and thus the valves.

This potential issue is starting to make me wonder if I want to own this pig, and I say pig with all due respect, much longer. Please call me a cynic as I don't believe the issue has been resolved with the PVC system that this car has.

I hope this leads to a useful discussion and in the meantime I will curse owning my first black daily driver and my obsession to have perfect swirl free paint.

Happy Superbowl Sunday!!!

[DeerHunter]

Somebody has pulled the IM off an S4 motor (V6T) and it showed no signs of carbon buildup. Either Audi has figured out the "secret sauce" or force-inducted motors are less susceptible. I'm certainly hoping it's the latter.

[yas]

And yet, someone else had a V6T that required carbon cleaning. The issue with carbon buildup in the TFSI isn't solved by forced induction alone, and I don't believe Audi has made significant progress in quelling this issue.

That said, I haven't heard of any V8TT's with this problem, though that may simply be a factor of insufficient time.

[DeerHunter]

And yet, someone else had a V6T that required carbon cleaning. The issue with carbon buildup in the TFSI isn't solved by forced induction alone, and I don't believe Audi has made significant progress in quelling this issue.

That said, I haven't heard of any V8TT's with this problem, though that may simply be a factor of insufficient time.

That thread is an interesting read. Cole's Notes: The root of the problem is lubricating oil leaking down the valve stems (which is completely normal in a healthy engine) which then catalyzes with the valve stem coating. Catch cans don't help because blow-by isn't the cause and water/meth injection is useless because it doesn't operate at low loads (when this reaction occurs). The good news is that forced induction engines inherently pull less oil through the valve stem seals, which means less carbon build up.

[Arnie49]

Carbon build up occurs do to failure to use a detergent gasoline. Audi lists recommended fuel in the owner's manual. BMW had a big issue with carbon build up a couple of years ago. They were not approving warranty repairs because they stated that it was due to not using recommended fuel. I use Shell gas and every 3 months I use Techron in the tank.

[DeerHunter]

Carbon build up occurs do to failure to use a detergent gasoline.

Carbon buildup in direct injection motors has essentially nothing to do with the quantity/quality of the detergent in your gas, for the simple reason that it does not flow over the components that are affected (e.g. intake valves) and therefore cannot help keep them clean. A good detergent gas can help keep your injectors and other fuel components clean, but that is a completely different issue.

[forza1976]

Carbon buildup in direct injection motors has essentially nothing to do with the quantity/quality of the detergent in your gas, for the simple reason that it does not flow over the components that are affected (e.g. intake valves) and therefore cannot help keep them clean. A good detergent gas can help keep your injectors and other fuel components clean, but that is a completely different issue.

This!

[kiku]

Real question is what's the approach for hot-V audi engines such as those in the S6/7 and RS7. Removing the intake for carbon clean up may require the removal of the engine.

[moosehead1]

Didn't think these powerplants needed preventative measures? I've only used catch cans on 'murican V8's, where they tend to gather 2-5 ounces of blow by between oil changes and help keep the throttle body clean. If needed the V8 obviously allows one to easily remove the TB from the top of the block with four seated bolts.

From my 5.7L Jeep Grand Cherokee, a mixture of snot, napalm, and molasses.