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Discussion Starter · #1 ·
I received a letter from Audi corporate about the possibility of carbon build-up on the cylinder heads. They are extending the warranty. Anybody get this? Know anything other than what was in the letter?
Thanks.
 

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New one to me. Every internal combustion engine will have carbon build up and I can't see why this is a particular issue for Audi Q5? You guys have tighter control on information manufacturer's are required to provide to consumers and Audi has been obliged to give extended warranties for issues in the USofA that they do not provide in EU. I would be interested to hear more.
 

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New one to me. Every internal combustion engine will have carbon build up and I can't see why this is a particular issue for Audi Q5? You guys have tighter control on information manufacturer's are required to provide to consumers and Audi has been obliged to give extended warranties for issues in the USofA that they do not provide in EU. I would be interested to hear more.
Agreed. Any chance of posting the contents of the letter?
 

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Is the carbon build up due to the oil consumption?
I cannot see it front the combustion of the petrol/gas
 

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Guess they run very lean.
 

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In their efforts to wring more power and efficiency from the internal combustion engine, automakers are increasingly turning to gasoline direct-injection technology - also known as GDI or DI. Originally developed to produce more economical and quieter combustion for diesel engines, DI is inherently more efficient and helps generate more power than port injection.

But there has been a dark side to the technology: carbon build-up around intake valves that, over time, can degrade power and efficiency, eroding the bonus DI is supposed to provide. While there's evidence that the most recent designs and technical enhancements have greatly reduced the issue, carbon buildup has been a distinct and well-documented issue in some DI engines from a variety of manufacturers over the last few years.

Known Problems
A U.S. patent application filed in 2002 by Volkswagen AG explains the DI-engine carbon-deposit dilemma this way: "Gasoline engines with direct injection of the fuel into the combustion chamber…suffer especially from the problem of the formation of carbon deposits…especially in the neck region of the intake valves."

The document describes these deposits as a sticky coating of oil and fuel constituents that, once formed, serves as a base for further deposits, creating "a circular process, by which the coating thickness of the carbon deposits continuously increases." Excessive carbon deposits "have extremely negative effects," the patent application concludes, citing significant performance losses, sporadic ignition failures and, potentially, holes burned in the structure of the catalytic converter (should bits of carbon break from the valves and pass though the combustion chamber).

The main purpose of VW's patent application was to propose a fix for DI engine carbon deposits: specifically, applying "a catalytic surface" to the engine valves that "counteracts the formation of carbon deposits." But nearly 10 years later, there's ample evidence that this and other potential solutions have failed.

"The loss of performance became very noticeable over time,"

Tony Chick, principal engineer at European Performance Labs in Stratford, Connecticut, has made a career of repairing and rebuilding high-performance engines from Audi, Porsche AG and BMW, among others and his operation has garnered a reputation among car enthusiasts as a go-to place for cleaning DI engines that have become choked with carbon. Chick thinks the problem for most affected engines can be traced to the breathing system - specifically, the design of its crankcase ventilation and exhaust-gas recirculation components.

All modern gasoline engines return some crankcase and exhaust gases back through the intake manifold in order to help control emissions, but, according to Chick, some exhaust-gas recirculation designs are "dirtier" than others. Some, he said, are less-effective at preventing the passage of tiny bits of oil, carbon and other particulates that eventually get baked onto the intake ports and valves.

If he's right, the rapid adoption of DI has actually illuminated an issue, not caused one. A "dirty" intake or exhaust-recirculation design can easily go undetected in a conventional port-injected engine due to the cleaning effect of gasoline passing over the intake valves. When the same engine designs are adapted to direct-injection fueling, however, that cleaning effect is suddenly lost - and the carbon layers can build.

There is no simple fix for engines that are prone to carbon build-up, Chick says. What's needed is a complete redesign of the crankcase ventilation and exhaust-gas recirculation systems to prevent particulates from getting through. Fortunately, the manufacturers whose engines are frequently cited in carbon build-up reports - mainly VW, Audi and Lexus .

Unfortunately the 20T engines are impacted particularly hard by this problem and still no fix in sight...
 

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The letter specifically stated cylinder heads. No mention of intake valves. Thanks for the info. Interesting.
I would take "cylinder head" as meaning the assembly which would include valves etc. big issue with carbon build up on fsi engines due to exhaust gas re circulation increasing carbon content by mixing carbon rich exhaust gas back into the intake manifold. I had a B7 RS4 which felt about 30-40hp down due to carbon build up.

On lower tuned engines may not be so much of an issue but a turbo would amplify the problem I guess hence the big problem with 20v T engines.
 

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The 20Ts only have 4valves per cylinder on the EA113 and newer EA888 (16v)
The 1.8T 20Vs went away many years ago, well before the Q5 came out.
 

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Discussion Starter · #11 ·
Could this carbon build-up be at least partially exacerbated by low tier/less detergent gas? I only run top tier gas such as Shell or Chevron but that may be because I am anal when it comes to what I put in my car. If high detergent gas helps, I don't expect any problems with carbon. Just thinking.
 

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Plenty of people have the problem regardless of fuel used - look on any of the VAG forums, be that VW/Audi/Seat/Skoda.
its a design issue around the use of feeding back exhaust gasses into the engine to reduce emissions.

heres and Audi one stating vpower since day one, still got the problems
http://forums.triplezoom.com/showthread.php?5144220-carbon-build-up-issues-how-common

just google, you see it (vpower) makes no difference.
Can i state it as fact? No. I'm no authority on engines, but even a quick check confirms its by far an isolated problem.
 
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