carbon collecting on the exhaust pipe

[Andy Leszczynski]

All Subarus I have seen (and some cars of other brands) tend to collect
some black (I guess it is carbon) stuff around the exhaust pipe.

But majority, even big truks have them just clean.

Anybody know why is that?

A.

 

[Rick Courtright]

All Subarus I have seen (and some cars of other brands) tend to collect
some black (I guess it is carbon) stuff around the exhaust pipe.

Hi,

My Subie's been "sooty" at the tail pipe since I got it at 209k miles
(still the same at 360k when it died), as was my Toyota truck (stolen at
136k.) My Camry is absolutely clean at 232k (rub a finger inside the
pipe and you don't even get a smudge.) Back in pre-smog days we'd have
said the sooty ones were running too rich, but nothing I've been told
about this "syndrome" really makes sense today, especially when the
vehicles run thru smog inspection: the Subie barely registers on most
scales they test for despite the fact it was burning a quart of oil in
400 miles at the last test, the Toy truck registered about as close to
zero as possible on all scales, yet the Camry is listed as a "borderline
polluter" or some such by the State of California cuz it's come in right
at the limit for one item twice after failing once. Guy at the smog
station says that's an indication the cat's probably on its way out.

So I quit worrying or even trying to figure this one out!

Rick

 

[Michael Pardee]

All Subarus I have seen (and some cars of other brands) tend to collect
some black (I guess it is carbon) stuff around the exhaust pipe.

But majority, even big truks have them just clean.

Anybody know why is that?

A.

Just guessing here... I think the soot around the tailpipe is because of air
flow there. If there is no easy way for air to flow past the exhaust pipe
the exhaust will swirl back and make a mess. I suppose you could clean it
off and experiment with little deflectors under the body around the pipe to
scoop some of the air past the exhaust. It shouldn't take much. There might
even be a market for a simple solution

Mike