Direct Injection's Achilles Heel

[ruff]

http://forums.audiworld.com/showthre...t=carbon+build

[RandyB]

Wow, that's terrible. I remember reading about it before on another site. I guess port injection isn't so bad after all.

[Finnegan]

I recall reading over on the e90 site that some 335i owners (335 is DI) have reported the same thing. There was some talk about methanol injection as a way to both cool the intake charge and "wash" the valves and [hopefully] prevent carbon buildup.

[foosh]

I drove a 2007 RS4 for 15K miles, and I only used Shell (Top Tier), unless I had no other choice. I only experienced the misfire once, which did set a code. A simple dealer reset did the trick. However, I am aware that it is a problem on direct injection engines.

Shell claims their latest "nitrogen-enriched" fuel is an attempt to try to deal with the problem. I have no idea whether their marketing claims have been verified by impartial technical analysis, but they claim the "nitrogen-enrichment" process makes the additive (cleaning) package more stable at the higher operating temps seen in such engines, thus making cleaning more reliable.

Only time will tell . . .

[swamp2]

Seems to be a case of a Achilles Heel to Audi's RS4 direct injection. Much, much more evidence would be required to call this an Achilles Heel in general.

[footie]

Originally Posted by foosh

I drove a 2007 RS4 for 15K miles, and I only used Shell (Top Tier), unless I had no other choice. I only experienced the misfire once, which did set a code. A simple dealer reset did the trick. However, I am aware that it is a problem on direct injection engines.

Shell claims their latest "nitrogen-enriched" fuel is an attempt to try to deal with the problem. I have no idea whether their marketing claims have been verified by impartial technical analysis, but they claim the "nitrogen-enrichment" process makes the additive (cleaning) package more stable at the higher operating temps seen in such engines, thus making cleaning more reliable.

Only time will tell . . .

I have heard similar comments about Texaco's Techron additive. There is no doubt that the fuel technology is playing catch-up at the moment but I don't think it will be much of a problem long term.

[quackbury]

Originally Posted by swamp2

Seems to be a case of a Achilles Heel to Audi's RS4 direct injection. Much, much more evidence would be required to call this an Achilles Heel in general.

If you read the thread (all 11 pages) the Audi techs report that it is happening in a variety of their engines, not just the RS4. So it would be fair to refer to this as an Audi problem, not just an RS4 problem.

Is the issue specific to Audi? (E.g. a defect withtheir oil pump design)? Or is it an artifact of direct injection itself (e.g. the intake valves not being cooled / cleaned by the incoming fuel charge)? Pretty important quesiton, and I think I would be inclined to hold off on getting a direct injeciton engine till this is sorted out.

I am reminded of defective seals in the original RX-7 rotary engines and defective seals in early turbocharged enngines. Not good.

[John@BMW]

yes, this is happening in all of our direct injection motors as well!

The 760 V12 motor gets it pretty bad and that is A LOT of valves to clean out every 35-50k miles. Factory warranty will pay for it but a CPO warranty will not!

I tell you what is really funny, when I talk to 'BMW technical services' about it each time a customer comes in for a misfire complaint which turns out to be valve deposit case, they say, " tell the customer to use good gas"

Then i say, WHY??? IT IS DIRECT INJECTION!!! YOU FOOLS!

This problem and the secondary air carbon deposit problem are all reasons why you should just flog the hell out of the engine every single time... If you drive them nice, they will kill themselves.

[GT3 Tim]

Originally Posted by John@BMW

This problem and the secondary air carbon deposit problem are all reasons why you should just flog the hell out of the engine every single time... If you drive them nice, they will kill themselves.

Indeed. A good flogging does wonders for the motor. Based on that, I am certain mine is clean as a whistle!

[JJM335]

Originally Posted by John@BMW

yes, this is happening in all of our direct injection motors as well!

The 760 V12 motor gets it pretty bad and that is A LOT of valves to clean out every 35-50k miles. Factory warranty will pay for it but a CPO warranty will not!

I tell you what is really funny, when I talk to 'BMW technical services' about it each time a customer comes in for a misfire complaint which turns out to be valve deposit case, they say, " tell the customer to use good gas"

Then i say, WHY??? IT IS DIRECT INJECTION!!! YOU FOOLS!

This problem and the secondary air carbon deposit problem are all reasons why you should just flog the hell out of the engine every single time... If you drive them nice, they will kill themselves.

Yeah...I think the point gets lost on some people that the gas never touches the valves in a DI engine.

[FStop7]

Interesting to see how Porsche deals with it. Their customers aren't going to tolerate problems with their DI engines like that.

I'm glad the M3 isn't DI (for now... I'm sure the problem will be fixed as DI evolves).

[Dascamel]

Originally Posted by GT3 Tim

Indeed. A good flogging does wonders for the motor. Based on that, I am certain mine is clean as a whistle!

Funny, I thought it was in my head that the car ran smoother after a good flogging. Makes sense though, extra heat and revolutions to break things down a bit.

[swamp2]

Thanks for the cross model and cross brand confirmations. It does indeed look to be a pretty serious general DI problem. This is quite surprising to me given the amount of very good research done on DI systems over a very long time period. If it requires as much frequent and labor cost as it must I can smell class actions.

[consolidated]

This is from a porscheplanet.net post, pics are supposedly of a 2008 Cayenne Turbo V8 DFI. Yikes. Remember all those posts from a year ago where people were bemoaning the M3 V8 not being DFI....?

[Sedan_Clan]

Damn! Those Cayenne valve pictures look nasty.

[Dascamel]

Wonder how the N54 valves look after 50k miles while running a tune.

[GT3 Tim]

Originally Posted by Dascamel

Funny, I thought it was in my head that the car ran smoother after a good flogging. Makes sense though, extra heat and revolutions to break things down a bit.

I recall my Dad telling me he had to "blow out the carbon once in a while" way back when I was a lil pup. lol. I guess he was right!

[GT3 Tim]

Originally Posted by Sedan_Clan

Damn! Those Cayenne valve pictures look nasty.

WOW...what else can I say.

[Gearhead999s]

I wonder how much the long oil change intervals are contributing to this problem?

[jym3]

According to this article:

http://www.bimmerfile.com/2009/05/01...pth/#more-2920

"BMW has not offered Direct Injection on any naturally aspirated (non-turbo) motor in the US due to the sulfur content of US fuel and they do not plan on offering it on them in the future (as we have been told)."

[footie]

The sulfur amount in fuel has been a long running issue in the UK, I remember an article run in one of the car mags stating that BMW advised it's owners not to use supermarket fuel. I can't say if this is still the case but it appears to be an on-going concern for BMW.

It's interesting that they see fit to offer it with turbo engines but not N/A engines. All I can say is that I have owned four DFI engined cars, 2 turboed and 2 N/A ones and none have caused any problems, I have always used super unleaded fuel either BP or Texaco. Maybe a quality brand of fuel is the most important thing.

[ideliver]

Originally Posted by GT3 Tim

I recall my Dad telling me he had to "blow out the carbon once in a while" way back when I was a lil pup. lol. I guess he was right!

we call it an "italian tune-up"