DWF

With all deference to those of you who have the 997.2 DFI cars I have a question. I have a 2009 Cayman and am thinking about moving to a 2009+ 911 but I'm concerned about all of the discussion of excess oil use and problems with DFI carbon build up. I understand that particularly with the carbon build up this is unsubstantiated but the excess oil use is indisputable. My car has no oil use problems and I basically love it but there is the appeal of having a 911. I'm not sure exactly what I'm looking for but perhaps some assurance I'm moving in the right direction.

zoomzoommo

2200 miles, one oil change, no oil usage so far for me, even after a track day.

Edgy01

Don't ever jump to conclusions. All new engine designs come with a learning curve. Porsche engineering rarely shares with their customers the discoveries that they make with respect to a new engine release. Despite several years of shaking out the new designs, only until they are in the hands of just regular drivers can they truly determine what they are going to do. The 997.2 engine probably uses no more oil than the 997.1 engines. Since we have no long term experience with the .2 engines yet it is anyone's guess what the LIMFAC (limiting factor) will become for that engine. Go back decades with Porsche and you will always find something that became an issue with their engines, from chain tensioners, to exploding air boxes, to prematurely wearing valve guides, to IMS, there is always something that ultimately causes Porsche to redesign their current engine. As Porsche tightens up their specifications on their vendor supplied parts (like HPF pumps) and fuel injectors, these nuisances will be less and less an issue. Remember, I have found that your style of driving, or that of the guy who broke in your used car's engine, will often have nothing at all to do with that engine's oil consumption. It can be a tolerance stackup that just added up in the wrong direction, and that means roughly 8% of these engines will habitually use what I consider excess oil. Try to remain positive about the other aspects of Porsche ownership which should eclipse any concern about having to dole out a little bit more in oil every year.

DWF

Excellent response. Thank you. One thing I have learned over the decades of car and motorcycle ownership is that they all have issues of varying degrees--some greater than others. As a relatively new Porsche owner I have been very impressed with the small number of complaints in the forums compared to for example BMW.

jumper5836

Other manufacturers that went DFI have encountered this issue, Porsche no doubt will have the same issues. The Cayenne was the first Porsche to have DFI. Maybe watch and ask a service rep about it, most owners seem to put the miles on them unlike the 911
I think though the new engine is a great engine. Just consider that every 75-100k it'll have the carbon build up and will have to be cleaned up and then it'll run like new again until it builds up again.

Fahrer

You are making an interesting point here. The base engine in the Boxster/Caymann has no IMS and no DFI. In my opinion, it will take time to see if the new engines do comsume more oil, on average. For the new engines Porsche did change how the inner cylinder surface is formed. This may or may not prove to be a factor.

As far as fuel systems are concerned, DFI has a ways to go before the bugs are worked out. I have a BMW 535 with DFI. It recently had a new high pressure fuel pump and all peizo injectors replaced and the car still does not run like it should.

I am happy with my 2008 C2S. Yes, it has an IMS but my feeling is thsat it is very unlikely to fail as it has the latest Porsche design and the car is well maintianed. I would gladly give up a few mpg and hp for the superior reliability of a port injected engine. My car is a keeper, not leased. Fewer headaches , more fun.

I believe that DFI is the future but it is not ready for prime time. One can see in Consumer Reports that the 2007 and 2008 911s have much better than average reliablity. This is not the case for the 2009s.

Indeed, the 2.9 might be the best design, overall.

Zeus993

Carbon build up? This is the first I have heard of this in a 997. The 993, yes. Tell me more. How would i recognize it? How do you get rid of it?

Fahrer

With DFI engines, the fuel is injected into the cylinder rather than the intake manifold. In addition the crankcase ventilation system takes hot oily air from the crankcase and brings it to the intake manifold where it can condense on the intake area of the head and bake until carbon is built up. With port injection the fuel (and the added detergents ) keep this area clean. Not so with DFI. One way to clean up the the mess is to take the intake manifold of and use solvents or mechanically clean the area. Some folks have reported the use of solvents inectedinto the intake manfold to clean up the carbon. I have no experience with either. I doubt very much that Porsche engines are immune from this.

With the 993 it is a different issue with carbon in the exhaust manifold plugging the aux air injection ports.

Finally, DFI engines produce more soot as some of the fuel spray hits the piston and forms carbon. The normal blowby in an engine may result in this increased soot building up in the crankcase and returned to the intake area via the crankcase ventilation system.

DWF

If you do a search you will find plenty of discussion on this topic. I have spent hours reading up on it.

DWF

That was sort of the conclusion I came to--2.9 has the new engine but no DFI. Interesting that you mention the BMW. I have a 335 and it to has recently had the high pressure fuel pump and injectors replaced. I'm looking at a 2009 911 that looks like a great car. The owner tells me he is adding a quart of oil about every 1,800 miles which falls well within what Porsche says is acceptable. I guess it's just a mental thing with me but that sounds like a lot coming from vehicles that use virtually no oil. This is a vehicle that has 7k miles. Do you guys think with additional miles it will continue to decrease oil use or at this point it's as good as it is going get?

saeyedoc

I have concerns about the DFI engines also, I decided to lease a new Cayman S (instead of buying) so I don't have to worry about it. I have had many problems with my 335i.

Edgy01

DWF--my 997.1 engine likes me to donate a quart every 1000 miles. I don't even need an odometer on that car--when it's asking for oil, it's another 1000 miles! I wouldn't be concerned about the quart every 1800 miles. I would be HAPPY to get that mileage!

stevepow

The best Porsche engine is the one you have in your garage.

BlueJay73

I just drove my new '11 997.2 3.8L DFI nearly 900 miles back from Naples, Fla. I had a '06 3.6L 997.1
The oil registered at the top bar when I stepped into it in Naples, and it still is at the same spot now. No measureable oil usage yet. I'm at 1050 miles now.
The difference in engines is tremendous (albeit, went from 3.6L 997.1 to 3.8L 997.2, so a lot of changes). I share concerns about top end gunk issues, but the engine is SOOOOO much better, I don't regret it for a second.
No IMS in nonDFI engine sounds good, but I don't know how much the DFI part of it affects things. All I know is my 3.8L 997.2 engine performs way better than the 3.6L 997.1 engine.

p.s.: Have not changed my avatar yet. Can't remember how to get proper sized megapixel image (haven't tried very hard--been driving).