Macster

There isn't.

In fact one could argu DFI engines with their higher output per liter displacement and better gas mileage generate less soot the non-DFI engines.

Macster

Go through any parking lot and all exhaust pipes have soot, are dark with the stuff.

All modern unmodified engines run at the same air:fuel mixture ratio almost all the time. This is approx. 14.7:1 as this air:fuel mixture when fed to a healthy engine generates exhaust gases that are most thoroughly processed by the converters.

Jaws1

Not true. My wife's Odyssey has virtually no soot in the tailpipe. My previous work vehilces (Avalanche, Silverado) had none. My 2008 MDX had none. My 2006 C2S had very little.

In my experience, a clear differentiation can be made between the DFI and non-DFI vehicles in the amount of tailpipe soot.

http://www.aqmd.gov/tao/Ultrafine_Pr...attiMaricq.pdf

kosmo

i think the OP's title "carbon buildup" could be misleading.
the soot can be totally different than carbon "build up"

if you wanna see real carbon build up go over the the Audi and BMW forums.

Fahrer

I agree. The carbon buildup with DI engines is the result of not having he benefit of the fuel "washing" the intake area. Non DI cars can produce some soot. DI engines produce more soot as a result of inadequate mixing of fuel and air.

Robocop305

I think Porsche engineers need to know this things are happening ASAP.

mopar bob

My biddies 78 Dodge Lil Red Express at start up will send the soot across the rear fenders of the truck. You wash and wax it to go to a show then you start it and S*** you need to wash again. He put on dump pipes just to start it. So go on a back road and have some fun and blow it out.

kosmo

Funny.this is an industry wide problem. However the auto cos arent too worried as these issues usually appear after the warranty period.

Wheres the emoticon for a hot potato ?!!

Dadio

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.

As it appeared in Excellence Magazine and mentioned in several of the previous posts.