I was at the Phoenix car show yesterday and pretty well all the car manufacturers were there. I talked to all of the people whose cars I was interested in and all said they had experienced some problems with the direct injection engines after miles were put on the vehicle. I was referring to the engines carboning. Everyone said all manufacturers with DI engines have had carbon problems and some turbo concerns. Even Mercedes were bobbing and weaving on this question not admitting a problem but not denying it either. They said you would be required to go in for more frequent service levels than before. That was the explanation.

So, is there anyone out there with any inside information of this problem if it's true or not what you learned or heard? Mercedes told me the EPA has mandated all cars are to be at a certain level or fuel efficiency by 2015 and therefore the DI and turbos to get more efficiency from these engines.

It sure find it frustrating when a potential buyer can't get an honest answer. Pretty soon all cars are going this DI way from what I saw.

Your input is appreciated.

Toban

 

Complete B.S.
I had a DI engine for three years and it was flawless.
All of my exchanges with forum member for that car and talking with my service manager has never mentioned "carboning"

 

Three years isn't sufficient. With our current sulfur content in the gas here in the US, the engine will foul, but that will take some time - 5 to 7 years, but I am confident that most of what I post is BS so do what you want. Personally I am holding off for several years before switching to DI because our gas is too 'dirty'.

 

DI engines will foul more than non DI engines and, like you said, the problems are more prevalent in the US.

We can only hope that manufacturers find a solution because DI is one of the easiest way to preserve power while increasing mileage. MB has been very conservative and does extensive testing in the US, so I'd opine that we don't have much to worry about. BMW, OTOH, is always on the forefront of bleeding edge technology so they get bitten more often.

Manufacturers have learned from the early days of catalytic converters and know that they can no longer sacrifice power and driveability for emissions/economy so they'll get this sorted out.

 

Not only D/I, but didn't M-B drop their "Lean Burn" function, or whatever it's called, in the U.S due to our dirty gas? Apparently the ROW new V6's get better MPG due to that feature.

 

Right, and MB isn't bringing start/stop technology here because of our sulfur laden gas and that effect on catalytic converters that need to stay really, really hot to burn that stuff off or self destruct.

It'll be interesting to see when BMW catalytic converters start to fail.

 

Who at a small-town auto show are you relying on to provide highly technical information? Most of the people that staff auto show booths are either hired lackeys, dealership salespeople, or low-level corporate employees. I'm quite confident that nobody who actually has a handle on engineering from Daimler, BMW AG, or VW AG (for example) made an appearance at the Phoenix auto show.

2012 AMGs.

 

Valves are kept clean by the additives in fuel. With direct injection, that fuel isn't flowing through the intake valves so the valves aren't kept clean. Toyota has gone so far as to combine DI with port injection to avoid the problem.

There is another thing to consider and that is engine oil being contaminated by the fuel because of the high pressure. I read a piece by an engine builder who said that with his DI engines, he changes oil more frequently (5K miles).

Added to that are other considerations including high pressure fuel pumps along with complex and expensive injectors.

Since the majority of E-Class owners lease their cars, they aren't concerned but for those of us who own our cars and hope to keep them for some time, it is a concern.

I decided to order a 2011 E550 when I learned what was coming in 2012. I have an engine that's been around for some time and according to the UK government tax data, it actually gets a bit better fuel economy than the 2012 E500 (E550 in the U.S.)

So if you lease your car or have deep pockets, you shouldn't worry. Otherwise, you should understand that there may be more maintenance costs down the road compared to cars with port injected engines.

 

buy a Mercedes extended warranty...that's what I'm doing

 

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Three years later MB may have decided that start/stop isn't an issue any longer in the US. My point was that MB often takes a more conservative approach while BMW jumps in head first.

 

This is partially inaccurate. The MB User Manual specifically notes that US consumers should research the Top Tier Gas list (toptiergasdotcom) and use gas from these manufacturers. In Europe, all the additives are required by law. In the US, they aren't and most budget gas stations don't add them even if you by 92+ octane. Bad engine design though is probably the biggest culprit. Some DI engines have minimal problems while others are awful. In general, I don't read about many Turbo or Supercharged DI engines having problems. It is almost exclusively naturally aspirated DI engines that have build up problems. Audi's design was/(is?) probably the worst in the business.

The NA DI 4.2L V8 in my last car (Audi S5) started having really bad cold starts and multiple cylinder misfires at 50k. At 55k, a couple chunks broke off and ruined two catalytic converters. Audi repaired under warranty, and tore down the engine to clean out the rest of the buildup. When I asked the tech what it looked like, he said one word "disgusting". In my research for other occurrences, many people didn't notice the loss of power, but did comment about a rough idle at start. They didn't do anything until the CEL came on. The DI problem is usually related to the EGR (Exhaust Gas Re-circulation) system. Some soot gets in there and over time it just continues to gum up and once a base coat is there, it gets worse exponentially faster. Some manufacturers use a catch-can design to protect it, other companies require the gas to have the additives, others use valve timing.

Here is a link to a great article on the problem: http://www.edmunds.com/autoobserver-...-adopters.html

I am hoping that MB did a great job with the design of the DI BiTurbo V8 in my car and the note in the manual about TopTier Gas is just a precaution. Here in SW PA, it is nearly impossible to find a gas station that is on the Top Tier Gas List. I am curious to see how the new 2012+ american models with DI 4 cylinders handle all the cheap gas here.

 

Really? I remember being a short blurb in Car and Driver (or one of the other auto mags) from a few yrs back that specifically stated MB had delayed introducing DI (which had already been available on their gas engines for several yrs) specifically b/c they were worried that the dirty gas in the US would cause a problem (what type of problem, they didn't say).

I'm only using Chevron gas in my C250 and crossing my fingers (and planning to sell the car around yr 5 when the new C's will have been out for 1-2 yrs).

 

Here's a thorough, albeit lengthy, thread on this topic from the C Class forum. Includes photos.

https://mbworld.org/forums/c-class-w...n-buildup.html

Regards,
Don

 

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Ref to the above comment. The BMW guys are catching on with the oil catch can fix.
http://www.burgertuning.com/BMW_335_oil_catch_can.html

We'll see how the E400 (3.0 turbo) will do ....

 

How did they fix the carbon buildup issues on diesel engines as they all are DI engines? Why have problems with gasoline DI engines now?

 

Gas is not equal to Diesel.

 

With DI, fuel is injected directly into the combustion chamber so it doesn't "wash" the intake port or the valve. Thus, at least in DI engines, fuel quality and additives are more important for reasons other than keeping the intake path clean

I'm not an automotive engineer (nor did I sleep in a Holiday Inn Express last night), but it seems fairly obvious the exhaust gasses (blow-by, oil, what have you) that get recirculated to cut emissions are the likely source for the gunk build up in intake ports and on intake valves.

Looks to me like an unexpected side effect of two efforts - reduce emissions and improve efficiency. I'm sure real engineers are beavering away on solutions.

 

Yes, diesel has more energy / weight than gasoline. I would think it has more impurities in about the same ratio too.

So how come diesel engines don't have the intake valve buildup issues?

 

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I'm very surprised that the 5.5L naturally aspirated got better fuel economy than a 4.7L twin turbo?

 

Excellent information in that thread, thanks. If you're interested in the subject I suggest reading it. Reader's digest version: "The deposits are from asphaltenes & other impurities etc. in the fuel, oil vapours from captive breathers & oil coming down valve guides. Mainly burnt VI Improver." Gasoline does play an important part and the thread explains why.

 

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