johnny goose

after driving the dfi motor there is no dought in my mind that this will be the next norm foe all engines...not only performance wise but economy to boot..my question is bein that there new on gas motors what reliability can we expect..ive heard that numerous owners with diff.. car makes have been complaining bot carbon build up..has porsche done anything that we know of to correct a possible situation..ur thoughts..john

ADias

I raised this issue over a year ago not as a fact but as a question. It raised controversy but no confirmation of a problem. The DFI engine is new and not enough time passed to reveal problems. However in almost 2 years of existence and with some examples w/ 50k+ miles, there have been not reports of problems. In addition PAG used tthe same 9A1 block in the new Turbo. That is quite an endorsement of the reliability of the 9A1 engine.

johnny goose

yes def a reliable block but direct injection is a new type of spoon that no one knws about..correct me if im wrong but does porsche use this dfi in thers racing program..i remember reading that it was in the spyder race car or the new gt3 cup car..

wwest

Most current uses of DFI involve some form of FI, Forced Induction, Turbo or SC. That way the only time maximum compression is used is at or near WOT. Supposedly rare events, those.

I suspect that what the future holds is a combination of DFI and Atkinson cycle. Only run the engine with the DFI "standard" 12:1 compression ratio at or near WOT. Otherwise use Atkinson to reduce the CR to 10:1 with SFI.

ADias

The ALMS LMP2 RS Spyder engine is DFI.

jumper5836

Yes and it isn't expected to run more then a few races.

savyboy

Due to "severe carbon build up"?

Fahrer

The issue raised by the OP is about carbon buildup, not engine failure or life. Carbon build up may be a problem. There just aren't many Porshces out there that have DI. The big one is VW/Audi. I would watch that braand to see if carbon buildup is a problem. As long at there is crankcase ventilation and not port injection carbon buildup might be an issue. Althuogh, it migh simply be the "big tune up" of the future, removing the intake manifold and using solvents, vacuum, whatever to clean it up. It is not the end of the world. The big question for me is..... does the carbon build up a bit and level off or does it get increasing built up over time? If it is the former it might be something relatively mior that most folks will ignore. The latter would require the big tune up.

alexb76

Before I bought my 997.1, was thinking of buying and RS4 (with FSI) and the carbon build up was noted as one of the issues with those cars, without a remedy (one of the reasons of leaning towards 997).

Some folks had their engines rebuilt by Audi under warranty, but since that car was also new, there wasn't much long-term information on carbon build up and the issues it has caused.

johnny goose

as far as i knw its a pretty big issue with audi and people are losing about 20hp every 25k.. which probably wont mean much...cel lights are comming up at about 40-60 th miles.. which might be a warrenty problem..we have to keep on eye on the high milege cars...also audi shops are charging about 1k for a ported clean up..how hard and how much work is needed to take off the heads on a porsche..

ADias

This has been debated to death. BMW and Audi DFI engines are radically different. The 9A1 DFI has a new head design and chances are intake gunk may not be an issue. None has been reported in 9A1 engines w/ 50k+ miles so far.

BTW... the issue is not carbon buildup. The potential gunk accumulation behind intake valves is not hard carbon deposits. If it will occur... it is soft oily gunk that can be cleaned with a Top Engine cleaner.

The funny thing is that the posters with a sky-is-falling concern seem to be 997.1 owners. I wonder why?

wwest

Hmmm..

Is that possibly why the Lexus GS series uses two sets of injectors, DFI and SFI...??

Isn't it the case that DFI, along with the higher CR, is really only important at or near WOT when the cylinders are recieving a full charge...?? No threat of detonation when the effective compression ratio is lowered due to the cylinder only getting a partial charge.

Fahrer

Really....how many 9A1 engines have 50K+ miles on them? The number of Porsches with DFI is a relatively insignificant number compared with VW/Audi or with 996/986/987/997 models.

ADias

I know of 2 50k mile cars with no issues. And I believe that no news is good news.

In any case... I recommend that whoever has these concerns avoid the DFI. Of course, life is short and you do not know what you are missing.

alexb76

Since you are very familiar, is 9A1 totally different than the Cayenne DFI too?

I just came across these:

http://www.planet-9.com/cayman-boxst...-good-buy.html

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