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- Aug 19, 2017
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Yeah so you're using the venturi effect then. I remember that back when I had a B7. I never did get around to calculating the actual amount of negative pressure using that method because I got sick and tired of dealing with this PCV crap as I was in University and that was my first foray with direct injection motors. Between that - a timing belt, and the world's shittiest idle on the planet (and thus dicking around with VCDS/Vag-com), I sold the car and bought a car with port injection and ran that for a number of years. (literally, from a terrible ownership experience with the Audi to a very positive one with MB).Oh, yea. I remember those things now. I have my crankcase vta running under my car which would help create negative pressure simply due to moving air while driving. As for oil leaks, I don't mind that as much as vacuum leaks coming from the crank case. It makes the ECU pissy and screws the car up.
Unfortunately these days there is no getting around direct injection engines but it has been quite a bit of time since my Audi experience. With the advent of 50800 engine oil, a built in engine air oil separator x2 on my car, and the fact that I will no longer own a car outside of warranty (by purchasing an extended warranty after the new vehicle limited warranty is finished), I can sleep better. Ultimately intake valve carbon buildup is not a 'servicable' item so if I do have a CEL as a result or a terrible idle, my extended warranty can deal with the consequences.
If they deny the claim, well, I'll be back at it with a manual clean, but the odds of that, now, are very low. Slightly unrelated to this, I've seen some 100,000 mile + M276 engines now (MB DI motors) that have a very clean intake valve despite the high mileage. MB's DI implementation from this model onwards also had the engine air oil separator so I think the whole carbon intake buildup thing is now a thing of the past and that perhaps people are still making a mountain out of a molehill but we'll see!
It is probably worth also noting that engine air oil separators are not 100%. When I pull the exhaust portion of the PCV valve (I just gave it a name....) there is still oil residue, just as would be the same with said 'exhaust' out of a catch can.
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The real question is whether or not carbon buildup reaches SSA (steady state accumulation). I believe it will, with these systems now in place + PEA + 50800 oil (for Audis, or SN Plus oils for other DI motors), and when it does reach SSA it shouldn't cause an issue.
That said, give me some time, miles on the road, and a wrench or 16 and I'll pull my intake manifold myself and take a look