plat27265

Might as well add in a good walnut blasting to clean off the carbon built-up behing the intake valves. Definitely worth doing if the car is going to for for another 30k miles.

SloopJohnB@mac.com

engines isn't covered by the CPO. Audi is in denial about it as well as BMW, even though BMW has specialized machines for blasting it. It's one of the reasons I'm holding off buying S8 twin turbo until/unless Audi covers carbon buildup on their direct injected engines. IMHO it's a design flaw caused by inadequate control of exhaust gas and/or positive crankcase ventilation (injection of crankcase gases including oil vapor) into the intake manifold or intake ports. A DI engine has only air going into the intake ports, so what exactly is causing the carbon buildup? Audi knows but is either unable or unwilling to cure the problem.

Right now I really don't give a dam because I have two leased B8 cars and a port-injected BMW M3...but sooner or later I'll have to change out the cars and most cars today are DI...but only BMW and Audi seem to have the carbon buildup problem.

jschrauwen

I like this guy. He's nailed the issue of carbon build up for the VAG and some of the options available.
Since I plan on keeping the car for a lot of years, I'm leaning towards removing the PCV's and plumbing in a nice catch can set up.
I haven't researched the topic in depth yet and if that process would cause any sort of codes coming up which would prevent me from passing emissions test in my area.

SloopJohnB@mac.com

It's not the codes but rather the oil contamination and shortened oil change intervals. Back in the days before PCV oil got contaminated a lot faster than after PCV was mandated. Not many emission regs resulted in benefits to the customer, but PCV was one in the sense of oil stayed serviceable longer. Another bennie was leaded gasoline, FWIW....exhaust systems lasted a LOT longer and so did spark plugs.

Wake96c4

That's exactly the problem on why DI engines have carbon buildup problems that conventional fuel injected engines don't. The fuel that used to be injected at the back of the intake valve constantly washes it. Now you have oil vapors settling on a hot intake valve with no washing occurring and over time it builds up into what he showed in his video.

I have a catch can installed on my Escalade and will put one on my next vehicle if it is a DI engine. Even in non-DI engines the valves don't get gummed up but the throttle bodies usually do which affects drivability as well.

I think a catch can would only cause a problem for passing emissions if you live in a state like CA. They don't like anything that isn't stock and sometimes don't even know what an EO is for a CA certified aftermarket part.

SloopJohnB@mac.com

as long as the OEM PCV system is still there. You can argue that a catch can would increase the volume available for oil vapors to condense but an amount of air would still be circulated through the engine. If you disable the PCV system entirely and replace it with a catch can you are clearly violating federal and probably state emissions laws not to mention seriously decreasing the life of the oil in your engine if not the lifespan of the engine.

I'd be more likely to install a methanol/water injection system to keep intake valves (and combustion chamber!) deposits at bay. They've been around for decades and work well. BMW has even used it on one or two of their current vehicles/engines as I understand it.

jschrauwen

MY bad. I don't plan on deleting the PCV system when/if I do a catch can install. Sorry about that guys.
I wish there were viable hydrogen cleaning facilities in North America. I've seen some great things resulting from that carbon cleaning process which seems to be quite popular in the UK.