London Banter - View Single Post - Buses

Guy Perry · January 15th 05, 08:55 AM posted to uk.transport.london

wrote:
Apples wrote:
I quite often see (and sometimes get on)
buses which have just come from the garage that are giving off a
pretty large amount of blue smokey exhaust...
What I was wondering was whether these buses have some sort of engine
damage, or whether they need to warm up properly.

I am no expert but as a former diesel car owner, a diesel will always
smoke a bit on start up as you are pumping unburnt fuel into the
exhaust until the engine fires up. I guess in cold weather this will
condense in the exhaust system then evapourate out over time. But 10
minutes seems excessive. My car would smoke a bit for the first few
hundred yards and that was all. A bigger diesel may behave differently.

Warm up is the main reason. For the comparison with cars, the only thing
cars and buses have in common is that the engine works the same way yet
that's about it. AFAIK the biggest diesel in cars was the Mercedes 300D
(6 cylinder 3.0 litres) the most common are about 2 litres now. The most
common bus engine will be around 10 to 12 litres (the smallest about 7
litres going up to 14 in coaches). These things do behave a little
different, especially when cold.

Yet there could be another reason: additional heating system (like
Webasto or Eberspächer). These tend to smoke quite a bit too.
As for that I've recently seen a car smoking like hell from the engine
compartment (wheel housing to be precise) but it was certainly not from
the engine itself. From what I know it looked more like heating.