DFI engines - any evidence of carbon build-up?

[braddo]

Porsche's direct injection (DFI) petrol engines have been around for over a decade now with the flat 6s in the sports cars and V8s in the Cayenne and Panamera. It would be interesting to hear of any accounts about whether these engines are susceptible to carbon build-up on the intake valves and inlet ports etc.

Has anyone heard of these engines suffering building up and needing a 'de-coke'? I have seen very, very little online about DFI Porsches, whereas Audi's RS V8 seems to be famous for it!

I have a high mileage 4.8 Cayenne and I sometime wonder if its performance and fuel economy have worsened over time. Am wondering about getting a boroscope and/or compression test (occasional blue smoke on startup).

[TDT]

DFI by definition means that there will be some build up over time.
The only way to not have it is to also have port injection so that the fuel cleans the deposits off the valve.

I've seen some reports of this over on other sites for 9A1 engines.

[Porsche911R]

What they did was make the oil run much much hotter in dfi engines it cured the issues most of the time.

[ChrisW.]

Certainly my GT4 runs up to 120C ... as mentioned previously the Clubsports run up to 150C in racing with no failures.

Looking at the oil temperature gauge against the actual temperature ... I would say that is the full-scale deflection and just into the red zone ...

[braddo]

ChrisW. said:

Certainly my GT4 runs up to 120C ... as mentioned previously the Clubsports run up to 150C in racing with no failures.

Looking at the oil temperature gauge against the actual temperature ... I would say that is the full-scale deflection and just into the red zone ...

Sorry but what your last sentence mean?

[Cheib]

I'd speak to someone like Hartech....best known for their IMS repairs but they have experience of DFI engines in 997's so I would think might be able to help.

[cd1957]

Hi been working on a few 10 plate and onwards in last few months.
I had to remove inlet manifold on some,and yes valves completely carboned u.
The 10 plate Turbo S,with 50k on it was the worst,but its a motorway car.

Chris

[ATM]

As an owner can I ask how to minimise this. Is it a matter of kicking the A out of the car regularly?

[ChrisW.]

braddo said:

Sorry but what your last sentence mean?

Sorry The oil temperature gauge on the GT4 shows a gauge and a temperature ... I estimate that the full scale deflection of the oil temperature gauge would equate to a little under 150C as it goes into the red ...

[ChrisW.]

As mentioned on other topics I have had my GT4 tuned to 340 ft lbs and 425 bhp ... there was no question in tuning at 20,000 miles that it may have needed a de-coke ... it didn't and it produced the numbers.

But, a third of that mileage will be on track and it is ridiculously over-serviced ...

And it is magnificent !!!

[braddo]

cd1957 said:

Hi been working on a few 10 plate and onwards in last few months.
I had to remove inlet manifold on some,and yes valves completely carboned u.
The 10 plate Turbo S,with 50k on it was the worst,but its a motorway car.

Chris

Thanks. Did any of them warrant any remedial work?