How to tell if carbon cleaning is necessary?

[midgaze]

Hi All,

I've got a 2014 RS5 with about 40k on the clock. I'm the second owner, and have put about half of those miles on her. Many short drives, some longer ones, and no shortage of revs into 7000 territory. I have noticed that in the past months (especially while cold) the engine sounds a little "rough", as if there is a bit of a scratchy sound that wasn't there before. I suspect maybe carbon, but I have no idea what I'm looking for.

I have watched the carbon cleaning DIY videos from the Ape Factory carbon cleaning thread, and it almost looks worth paying the $1300 a local shop wants for the job (favorite post: "Lots of carbon. Still going at it. No longer fun.").

Do I have to take off the upper and lower intake manifolds to know if there is carbon buildup in there? If I can get in there with a $30 endoscope in one of the spark plug holes that would be nice.

[TSlice]

Going in through the spark plug hole puts you in the combustion chamber and you need to see the backs of the intake valves. You might be able to fish a long endoscope through the intake tract with a little bit of disassembly (pull off the throttle body), but it will be a challenge to fish it through and avoid obstacles such as the tumbling flaps. If you can snatch an endoscope for $30, might be worth a shot because it would certainly be less involved than pulling the intake manifold.

[findalex]

It could just be the injectors, although you almost certainly have carbon buildup. It's just a question of how bad it is and if it affects the performance of your engine enough.

With car repairs, I like to start with the cheapest/easiest thing to try first. In your case, I would start with a bottle of BG 44K @ $20. Just pour into gas tank.

The second thing I would try is an intake valve cleaner made specifically for direct injection engines. CRC GDI IVD Intake cleaner has good reviews. Just spray into intake after the MAF. Some youtube videos show before/after and it really does a good job.

If all that fails, then I'd go with the walnut shell blasting. It's much easier than soaking/scraping, and it's safer because you're not scraping metal with metal and the walnut shells are soft enough. It's how BMW handles their carbon buildup problem. It's also something you can DIY. Check youtube. Some people also sell adapters, but I've seen videos where a big coolant hose works just as well.

[ENV²]

Did you do the spark plugs yet? If not, start there. I did mine at 40k and the car went fully smooth and felt like it gained power. They should be done every 35k

Sent from a misfiring cylinder

[midgaze]

Thanks for the replies. I'm going on a long drive in a couple weeks, and right before I hit the highway I'm going to do the CRC GDI IVD routine, and put a can of BG 44K in the tank. Then I'll just burn that tank of gas in one go, driving hard. Hopefully that will scare away any carbon I have in there for a while. Probably do that every 20k or so if it does any good.

I'll update this thread with any observations.

[Ape Factory]

Ha! Had a good laugh at my own quote. If you can't laugh at yourself... But anyway on the in-tank cleaners...those'll maybe work to help clean the fuel system innards but will do zero for any carbon buildup in the intake tract. Fuel never hits any of those components which is why carbon buildup is a real thing. So if you're suffering some ill effect from carbon buildup, the in-tank stuff is not going to change your car's behavior.

If you're happy with the car's performance currently, maybe wait 10K miles. If performance is the #1 priority and the cost of having it done correctly is not prohibitive, I'd do it. Whether there are symptoms or not, have no doubt that the carbon is there and it has lessened the engine's ability to breathe.

If you haven't done it already, the suggestion to change the spark plugs is a good one. They're supposed to last 60K miles I believe but it'll make a difference if you change them every 35K. I could run a car on the dyno, swap in new plugs while strapped down, run it again and gain 5-10 hp.

On visually checking, you cannot check through the spark plug hole as you're peering into the combustion chamber and all the carbon buildup is in the intake runners. People have snaked cams through the intake manifolds to take a peek at the intake runners and determine the extent of buildup.

Carbon cleaning yourself is doable but I'd say it's not for the meek or anyone who can't problem solve mechanicals. A larger compressor would have made it much easier, it would have gone much more quickly and consequently, I would have had much more fun through the whole process. i'm a bit of a masochist however, so take fun with a grain of salt.

[Hy Octane]

Been using this product since the day I got my 2013 S5 and after almost 7 years and 60k+ miles, I have no measurable carbon deposits on my valves. While the fuel may not wash over the valves, the recycled unburnt exhaust gases from the PCV do (this is what causes the carbon buildup in these direct injection engines) and within those gases are the lubricating and cleansing agents of this amazing octane boost/additive. Not sure how well it will clean already carbonized valves, but as I say, been using it since new and having just had a service last week there is no problem on mine as the lubricants and cleaners in the additive get deposited on the valves instead of carbon. Think of it as coating them with teflon as it were. Nothing sticks!

http://bndautomotive.com/aces-formul...oline-formula/

If you have any questions call Brian at the number on the page and have him explain the theory to you. He is quite brilliant and an amazing molecular engineer. All the Audi guys use this stuff on their RS's and S's over at RS6.com.. I used to have an RS6 and used it in the tank for 10 years.. never had a problem. Takes 91 pump gas and boosts it to 101 octane.. only 1 oz per 6 gallons of gas.. Enjoy!

[Ape Factory]

PCV recycles crankcase air and gasses, not combustion gasses. That's the EGR system which is only operational for a very short period of time at startup. The air/gas in the PCV system will contain micro oil particles (hence the complex air/oil separators incorporated into the system) as well as volatiles (vapor) gassed off from hot oil and any fuel/hydrocarbons which makes its way past the rings and into the crankcase. So any fuel additive isn't really going to change the chemical composition of the gas that makes it past the rings (most of which happens when the engine is cold and as it warms up) or the oil itself. Anything that's injected into the cylinder goes through a chemical change due to ignition.

DI engines are pretty damn efficient but there are partially burned hydrocarbons which make their way to the intake port via valve overlap during the combustion cycle. But again, they're burned for the most part and have gone through a chemical change due to heat. The hydrocarbons blow over and get baked on the valves, layer after layer, until you have carbon buildup that's plainly visible. Fuel formulas for DI engines haven't really changed (other than the introduction of ethanol as a mainstream fuel) but oils have. That should tell you something.

The lubricity of fuel was an interesting topic when the EPA eliminated leaded gas in the early 70's. There was a big fear it would cause premature wear on valve guides and seats and head rebuilds would be very common. Those issues never really appeared and it's more myth than fact. He talks about fuel providing lubrication for the cylinder walls and piston rings on his page but that's the job of oil, not fuel, and fuel wash can lead to premature wear because there's no oil providing lubrication. So I have to take all of what he says with a big grain of salt. Fuels can be "dry" like LNG but they most affect components in the fuel system itself like fuel pumps. That's why flex fuel vehicles use different pumps and internal parts which are self lubricating.

I know someone here recently did a carbon clean on a high mileage S5 (3.0T) and there was very little carbon buildup compared to what we see on the RS5. So something in the design along with forced induction leads to less carbon being deposited on the valves.