I started this thread for discussion and information. I also talked to many contacts in the Porsche world and here is a summary of what I gathered:

The DFI engine brings a set of issues to deal with. These are just there and they are not necessarily game-stoppers. Understanding them is important. The following are procedures that should be followed w/ these engines:

1 - Avoid short trips. Always allow proper oil operating temp and temp cycle.

2 - Change oil more frequently - perhaps 5-6k. (15k oil changes were insane anyway)

3 - Do a 15k miles (or yearly) intake clean service using an appropriate intake cleaner product.

Hopefully, abiding by these rules, these engines will last and be trouble free.

 

Thanks for the info. The shortest trip from my house to somwhere I would go is 6 miles. This is a fav resturant of my wife and I go to...we would like to take the Porsche but this would be consider a short trip because the oil is not hot by then. My wife thinks this is absolutly ridiculous...I tend to agree with her.
We use to take our 06 and 07 on this short trip each week with out any issues. I am a little taken back about the issues with our new 09 C2S. The car is not very enjoyable or easy to live with under these circumstances.

So so far:
I have done 2 oil changes with in 6000 miles.
Avoid short trips...everything is 10 miles plus

The car burns oil and soots up the rear....

 

I think that more 997.2 cars need to make their way to service in order for technicains to diagnose these problems . As for Porsche releasing a car with these issues -- inexcusable . Whether it's a 36 mo lease or a long term commitment no owner should ever have to buy car with these problems or doubts . Especially a Porsche , especially a 100K car , and even more so at an economic time when every dollar counts .

In my opinion if "short trips" and "frequent oil change" are criteria to adhere to I feel its time that Porsche write this into the manual and service program so that a buyer knows what he's getting straight from the top . In the light of thse recent DFI concerns it may be time for Porsche to offer a free maintenance program for 09 DFI cars and resolve these matters quickly so that these issues do not carry over into 2010 cars .

 

I would not go so far as that. What is wrong is if the number of small trips is significant compared to the number of longer trips. I drive a car 2 miles if i need to, I just do not drive the same car 2-mile trips one trip after the other.

 

I use my car on a regular basis...some short trips...some long trips...It is DFI and I have NO soot at all. I did however change the oil at 2000 miles and I can see it maybe needing some oil added now that Im at about 4500 miles.
The car rides great, I have no issues to report.
Just my experience.
Oh...by the way...Most of my driving is spirited.

 

This is absolutely inevitable with DFI engines.

The backs of the inlet valves on conventional fuel injection engines are both cooled by the injected fuel and kept clean by the detergent and other additives in the fuel. This simply does not happen with a DFI engine as the fuel is injected directly into the combustion chamber (i.e. on the other side of the valve). This means oil from the valve guides will inevitably get on the back of the (now much hotter) valve, not be washed away by the fuel and in short-order gunk eveything up as in the picture.

This will cause the performance of DFI engines to drop away noticeably and quickly with age as the inlet valves will be less able to pass air into the engine. It is also only able to be cured by substantial re-engineering of the inlet valve guide oiling system (effectively a new cylinder head design) that seals the inlet ports from the oil. Not something I can imagine Porsche paying for....

 

Yuck, that aint good.

 

At first the comments about more regular oil changes in response to this problem did not make sense to me. Like Ian my immediate reaction is that as the fuel is now not "washing" the rear of the valves then carbon build-up there is more likely.

I recall a similar and well known problem with the old Land Rover V8 engines when oil changes were skipped. They developed carbon build up on the valve stems, leading to sticking valves in light throttle openings. Sounds familiar and I can only speculate that it was actually the deposits in the oil accentuating that build up process. The fix, apart from a couple of good oil system flushes, was a heavy dose of inlet system cleaner. If that didnt work it was heads off for a good old fashioned de-coke.

 

I don't think it's a carbon problem, diesels have been dealing with this for years. Degradation of oil is common.

If this is effecting the the intakes valves, then what about the valve seats?? and again the MFS

 

'Carbon deposits' has been used loosely in this thread. This is condensed material from the evaporative system - oil sludge. I am now convinced that it can be minimized avoiding short drives and periodically using an engine cleaner.

 

Is it from the evaporative system? To me it looks more like oil running down from the guides and gunking up on the back of the valve head? I guess it could also be a combination of both.

Either way, both would be washed away by the incoming fuel on a non-DFI engine. It's not uncommon these days on a regular fuel-injection engine for the valve backs to be totally clean even at high mileage if a good-quality fuel (with a well-designed additive package) has been regularly used. DFI definitely changes this for the worse.

 

Has anyone talked to their Porsche dealer or to PCNA about this specific problem? (or has it even been complained about with the new 997.2 being so new?). A lot of the things mentioned in earlier posts make sense, but I find it hard to believe that with Audi's several years of DFI engine experience (and their affiliation with the Porsche clan) that the Porsche engine engineers would design the 9A1 engine with such an obvious flaw! The problem may exist in the Cayenne DFI V-8, but does that mean that we must also have a problem in the 9A1 engine as well? Where is the evidence from the 997.2 cars? I am concerned but not worried yet. BTW, my Porsche dealer here in the Phoenix area has not heard a thing about this "problem" and has not had any 997.2's or Cayenne's with this problem.

 

^^was thinking the same thing. Why, if this has been a recent concern with DFI engines in Audi's, would Porsche do the same thing at a later date without a "fix" implemented.

J

 

I agree with you. I do not know what's going on specifically on the 9A1 engine. I started the thread asking exactly that question and using the Cayenne as an example. It's possible that given the boxer design this issue may be different on the 9A1. I suspect though that the potential for oily gunk buildup on the DFI air intake is there.

 

+1!! Diesel engines inject directly into the cylinder. Diesels don't have this problem.