Is Carbon Buildup a Problem With Direct-Injection Engines? - Mercedes-Benz Forum

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post #1 of 6 (permalink) Old 01-16-2015, 07:25 AM Thread Starter
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Is Carbon Buildup a Problem With Direct-Injection Engines?

Direct injection offers numerous benefits over port fuel delivery but could it be a bigger headache than it’s worth?

The automotive industry has gradually switched to direct injection over the past decade or so and for good reason. Spraying a precisely controlled amount of fuel right into an engine’s combustion chambers can result in improved efficiency and greater power density; tailpipe emissions are generally cleaner as well.

In spite of these advantages, this technology isn’t perfect. DI has a handful of downsides including additional noise, particularly at idle and dramatically higher costs, though there are other concerns.

And a big one has to do with carbon deposits. We’ve heard rumblings that blackened buildup on the backsides of intake valves is a major problem and something that could be disastrous for motorists in the coming years. To get to the bottom of this potential top-end issue we did some digging.

What’s Really Going On?

Ford has been pushing its EcoBoost engines as a way of improving fuel economy without sacrificing performance. The real-world results of this strategy may be mixed, but one thing is not: all of these powerplants feature direct injection as well as turbochargers and advanced control software.

These engines have been on the market for a number of years now and to get some empirical evidence from the front lines about how they’re holding up we reached out to Brian Laskowski, a Ford Factory Certified Technician. He also has a YouTube channel, FordTechMakuloco that highlights all sorts of automotive repairs.

Responding via e-mail Laskowski said, “Carbon deposits in Ford engines are not a widespread issue due to the advanced engine technology.” But he also mentioned that it has happened in some low-mileage EcoBoost units.

“As of today the issue seems to be isolated to certain markets with varying factors such as fuel quality,” said Laskowski. If carbon buildup becomes severe he said it can result in all kinds of issues from drivability woes to misfires, turbocharger issues and even catalytic converter damage.

Survey Says…

Assuaging potential sky-is-falling fears, Michael Karesh, the developer of TrueDelta said carbon buildup is “not an issue for all direct-injected engines” based on the data he collects. His website surveys nearly 100,000 drivers of all makes and models to acquire relevant and timely data about vehicle reliability and fuel economy among other things.

But of course there are some instances of deposit-related issues that have popped up. Karesh said, “The only engines it’s reported quite a bit is [with] the VW/Audi 2.0T and then the Audi V6s.” He also said, “I know there are some BMWs that end up with carbon buildup as well.”

As for the frequency of reported problems with these Volkswagen cars he said his numbers indicate “it can be as high as one in six over the last two years,” which “is a high number” and one that he said is consistent across different models.

The 2008 Audi A3, which offered a 2.0-liter turbocharged four-cylinder engine, also popped up in the TrueDelta data. Karesh said it’s puzzling why 2006 and 2007 models aren’t having similar carbon issues. Leaving us with more questions he said, “I’m not really seeing GTIs [popup],” which are mechanically similar to the A3.

“If there is a non-German car there might be something happening in the [Cadillac] CTS,” said Karesh, but once again he cautioned that it’s “too scattered and sporadic” to draw any definitive conclusions. Additionally he said, “I have one report of decarbonizing the engine in a Chevrolet Equinox.” Unlike the other instances, he has quite a large sample size for this particular vehicle, which clearly indicates that deposits are not a major problem at this time ...
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post #2 of 6 (permalink) Old 03-17-2015, 11:07 AM
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I am planning on getting a new car within the next year or so. While it is up in the air as to which model we buy, it will likely be a new Benz. I am leaning towards a Bluetec diesel, but with the CLA 250, it is only in petrol form within North America.

I've searched around and located no definitive info on whether M-B DI engines have suffered with the carbon build-up. I am guessing (Oy :-) ) that the issue has been resolved by M-B for their DI petrol engines (and diesel???) with extra fuel in the combustion chambers to clean the intake valves after combustion. This could be handled via the engine computer and/or with extra injectors, and/or multi-plugs. (Hmm, not sure about the last one.)

After searching around this forum, I've only seen the above article which I read before jumping on here.

So, does anyone have any info on IF the issue occurs with newer M-B engines and if so, what the M-B solution is? Seems that some mfgrs are ignoring it and others tackling it with better engine control via the computer.

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post #3 of 6 (permalink) Old 03-21-2015, 03:43 PM
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the topic of carbon build upon intake valves, is a topic that is gaining momentum on other car forums as well. but has been talked about since 2012
i have an Audi A8 as a daily driver so am on the audi forum.
the thread below highlights the issue well with pics.

Article about S6 V10 carbon build up. - A8 Parts Forum

audi engine specific? i have heard this issue on Ford engine and others .
i think it will be an industry issue due to the way direct injection works.
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post #4 of 6 (permalink) Old 09-29-2015, 05:47 PM
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Are any owners of Mercedes DI gasoline engines experiencing this problem?


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post #5 of 6 (permalink) Old 10-12-2015, 05:39 PM
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Carbon build up in a diesel engine is due to incomplete combustion over time. Short drives, low miles, not working the engine so that it gets to proper operating temps. The solution is to take a few longer drives that thrash the engine enough that it heats up very well, is worked to the fullest, and this tends to dislodge carbon in the engine. We call it an Italian Tune up. Find a very steep incline and power up the mountain so that the engine has to really work and gets to proper operating temp for a goodly time.

In a diesel the car will lay down a thick black cloud at high revs on the climb, then let loose some crap from the engine with a boom, smoke and you can feel there is a boost in performance. Takes a few attempts to knock the crap loose and out, but you get power back.

Maybe the "eco" crap cars are not being driven enough to really heat up the system. Add poor fuel, poor care, and the computer trying to over compensate. Carbon


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post #6 of 6 (permalink) Old 10-27-2015, 09:27 PM
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So it seems, new Benz gasoline DI turbo4's don't seem to have this carboning problem.


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