335i black soot

[Redrussell12]

So I cleaned my factory exhaust tips the other day cause they had some black spot on them. But after driving it once the black soot is back. I just got the car. Is this normal? It’s a 2013


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[mryakan]

Think about it, what do you expect to come out of the tailpipe when burning gasoline?

[328 Power 04]

Stoichiometric (afr of ~14.7:1) gasoline burning will be very much soot free. These cars run near stoich on gentle driving, sometimes even ultra lean burn for efficiency.

BUT, when you use full throttle, the 335i goes rich to about 11.5:1 to keep exhaust temps lower, to protect your turbo and catalytic. Running it slightly rich reduces the power (compared to stoichiometric for that air amount), and creates some minor soot due to some fuel not being fully burned.


If you have some soot, it may indicate you are driving the car hard often.

It's all perfectly normal as long as you don't have check engine on and/or failure of components.