Just wondered if * all * your petrol - engined cars are catalyzed
in your state ? Our cold limey weather does leave a lot of
rotten egg smells coming out of the pipe while the EGT rises high
enough ( on small 84 cubic inch engines & smaller still )  to get
the cat working. A real design & legislative mistake IMO !

We are also looking at looming plans to silence our motorbikes
to 74 dBl arrgghh!

Paul Lamar responded:

Yes I think they are. Rapid warm up is also given strict attention
with double valve thermostats that recirculate the coolant until
it gets hot. Engines less than 1.8 liter (100 ci) are rare however.
Only in the high mountains (2000 meters) do we see low temperatures
much less than 30 F.

Paul is speaking of California.  There are many parts of the US where
the winter low temperatures are below 0 degC (32 degF).  There are
winter days in the upper plains states (Nebraska, Wyoming, Montana,
Minnesota, the Dakotas) where the *highs* fail to break 0 degC.

Russell Kent