Yes,you are correct,I have not heard of problems related to carbon buildup in Porsche's DFI engines just yet. But let's keep in mind that they are fairly low miles.
I was certainly surprised to see the amount of carbon buildup on those pistons though!

 

Thanks for the link.
Sorry about the pompous title...that was all I could think of at that moment. Please feel free to suggest a more appropriate title and I will try to change it...

 

Possible explanation?

Excellence Magazine article posted by dadio a while back:

Porsche's official answer is....

Last fall we had an opportunity to ask a Porsche AG tour guide, Gerard, just why those DFI tips are often sooty black? His answer: To heat the catalytic converters rapidly during the cold start cycle, the DFI system deliberately runs a rich mixture to ignite fuel with the exhaust valve not fully closed. That heats the cats quickly to their optimum temperature and better meets emissions standards — the side effect is the carbon residue on the tips.

 

Just a data point from my first DFI 997.2 4S motor: it powered the car with out a hic-up for 67 track
days and the last oil analysis before selling the car with 24k miles was clean.

 

You are wrong. Rest assured, I for one, reading your comment, do not care at all what you think.

With all due respect.

 

Trade offs to everything...Cars are only designed to last long enough to last the warranty period it seems.

If I recall, it's recommended to walnut blast the intake at 30-50k. I don't think this is normally too expensive (~$500?), but I have no idea how difficult this is in the 991/981

 

No worries. Have a nice nite...

Mj

 

Good info. Just reiterates how much emissions has a stronghold on these manufacturers. Pretty damn sad. I wish they could leave our beloved sports cars alone...

 

I wonder if adding water injection would help. I've run it on my modified bolt on forced induction cars for years mostly to add timing but the side benefit is supposedly cleaner intake tract.

 

Absolutely. That is what some manufacturers are testing : port injection combined with direct injection. The port side injects water in some systems,which is basically such a fine mist that turns right away into vapors. Those vapors clean the back of the valves like nobody's business. And others are using port injection with gasoline,only that it's being sprayed on demand depending on certain conditions...like when more power is required from the engine.

 

Won't show in Oil Analysis. Have to look at the intake valves.

Well, on my wife's old Mini it was about $800 to do this. And the intake manifold is not hard to get to. On a modern 911, it would be easier to drop the motor than to pull all the accessories and the intake while in the car... most shops charge about 16 hours for a drop and install, plus pull the intake, walnut blast, etc.

I'll ask my shop's engine builder about this next time I'm in there. They do quite a bit of work on 9A1 motors but mostly turbos.

 

This makes me worry a bit more about owning a GT3 out of warranty.

Any way to get a cleaning covered under warranty besides blowing your entire engine?????

 

Irrelevant for the moment; the current GT3 and GT4 have a warranty...

 

for the moment yes, however I do like to consider the future.

 

So are we saying the Porsche engineers didn't know about this or should I say they knew but didn't care? I still find this hard to believe.