Originally Posted By Jappo
Originally Posted By Cicerone
Just the newness wearing off.


How do you mean? It's a 2003 S1 with 26K miles on it.


Sorry, an old joke.

Link to a few BMW forums (thought these may be more relevant than Toyota etc.):

http://www.m5board.com/vbulletin/e39-m5-e52-z8-discussion/99231-ammonia-smell-out-exhaust.html

http://forum.e46fanatics.com/showthread.php?t=301136

http://www.m3forum.net/m3forum/showthread.php?t=40302

Everything seems to point towards it not being uncommon and nothing to be worried about - seemingly they are post-filter fumes, something to do with the cats and various nitrogen doo-dads...

See also here:

http://www.wheels.ca/Article%20Category/article/31671

"BMW uses a particulate filter, right at the exhaust manifold, that traps the tiny soot particles in a complex honey-comb structure. When deemed necessary by the computing powers that be, the ECU adjusts various parameters of the fuel mixture and valve-timing to increase the exhaust temperature, and the particulates are burned off.

Now, about that pesky NOx. Just downstream from the particulate filter, liquid urea (a common organic compound made from ammonia and CO2) is injected into the exhaust stream. Here, it reverts back to ammonia and CO2, mixes with the NOx, and then the whole concoction is neutralized in the catalytic converter, emitting only nitrogen and oxygen. A small reservoir of urea is refilled at every service interval."

Last edited by Cicerone; 02/08/10 08:45 PM.