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-   -   9A2 tailpipe soot (https://rennlist.com/forums/991/1038572-9a2-tailpipe-soot.html)

Jaws1 12-09-2017 06:43 PM

9A2 tailpipe soot
 
i previously owned a 997.2 and was constantly having to clay bar the rear bumper in order to get rid of the exhaust soot. The car did burn a little bit of oil, but I think the soot was mostly a function of the DI. I picked up a .2 C2 yesterday and the tailpipes are remarkably soot-free. Is there a difference between the 9A1 and 9A2 to account for this difference?

subshooter 12-09-2017 06:56 PM

I have two Porsches, one with the 9A1 (38k miles) and the other with the 9A2 (5.2k miles). I have never experienced any soot on the bumper on either of them. I have a lot of soot that builds up on the 9A1 exhaust tips though. On my 991.2, it has black tips so it's hard to tell but the body is white and there is absolute no soot.

koala 12-09-2017 07:07 PM

Ethanol fuel seems to be a major contributor. I'm not sure about the USA, but here in Canada, Shell 91 is the only fuel in the entire country without any ethanol added.

That said, I run 94 because horsepower

Jaws1 12-09-2017 07:27 PM


Originally Posted by koala (Post 14659472)
Ethanol fuel seems to be a major contributor. I'm not sure about the USA, but here in Canada, Shell 91 is the only fuel in the entire country without any ethanol added.

That said, I run 94 because horsepower

My 997 only saw Shell because it is ethanol free. Iíve never heard of ethanol being a contributor to soot.

Rambler_13 12-09-2017 07:29 PM

My 997.2 definitely leaves a good amount of soot on the exhaust tips and sometimes will spray onto the bumper but it easily wipes off. I had 2 other 991 9A1s but they had black pipes and exterior so I couldn't tell. Other DI cars I've owned have done the same though.

DBH 12-09-2017 08:50 PM

Just for the record, my Cayman GTS with 9A1 threw a lot of soot out the pipes. I was constantly cleaning them. My current 911 GTS (9A2) has no evidence of soot at all. I don't know why? NA vs turbo?

Rambler_13 12-09-2017 10:15 PM


Originally Posted by DBH (Post 14659631)
Just for the record, my Cayman GTS with 9A1 threw a lot of soot out the pipes. I was constantly cleaning them. My current 911 GTS (9A2) has no evidence of soot at all. I don't know why? NA vs turbo?

I don't think that's the reason, my 997 is turbo.

Rambler_13 01-08-2018 01:47 PM

Deleted

Valvefloat991 01-08-2018 05:13 PM

DI typically produces more particulates in the exhaust because there is so much less time for the air and the fuel to thoroughly mix. That leaves pockets of slightly lean and slightly rich mixtures. The rich ones produce soot.

As the particulate emissions standards get tougher going forward, it is likely that some DI gasoline engines will need particulate traps in their exhaust systems, much like diesels. This is one reason that some newer engines are employing both port and direct injection on their engines.


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