[s-cars] (no subject)

[Brian Powell]

> My guess would be that it will run richer for a greater period of time
> if
> the car is sitting there idling, thereby polluting the air with greater
> quantities of crapola than if you were to start driving the car
> immediately.

Cold start emissions is the worst pollution your car is capable of.
You should always start your car and drive immediately so as to warm
the engine (and mostly the catalytic converter) quickly to reduce its
emissions.  It is not due to fuel/air mixture (though that plays a
minor role thanks to the engine seals, etc. are designed for normal
operating temperature) but that the catalytic converter does virtually
nothing until it is heated up.  NREL (about two miles from my house)
designed a catalytic converter that retains much of its heat and
reduces standard car emissions 91%.  Remember, if you take a 20 minute
drive, >60% of your emissions will be in the first 2 minutes while the
car warms up.  By letting the car idle, you are stretching this time
out much further.  Electric coolant heaters reduce many of the problems
associated with cold-start emissions by warming the engine and thus
heating the cat much quicker (not to mention your heater will be on
immediately).

Manufacturers (Audi is one of the leaders in this) are spending lots of
money to research this very topic.  There was an interesting article a
couple of years ago in European Car about the 1.8t engine's cold-start
emissions controls.  Cold start emissions are the major emissions
problem with gasoline cars and if we can eliminate them, we won't have
to drive a damn electric car.

As an oceanographer, I can tell you these emissions are affecting the
Earth's oceans (which are tightly coupled with our climate).  I can't
tell you what it will mean for us though.

Here is a blurb from NREL:

> This is good news for our environment. But not as good as it could be,
> because EPA standards primarily address pollutants that are emitted
> while a car is warmed up and running. They do not address the warm-up,
> or "cold-start," period, during which time today's cars and small
> trucks produce more than 50% of their emissions. The reason for so
> much emissions during the cold-start period is due to the fact that
> current-technology catalytic converters don't start to work until they
> reach a temperature of about 300 oC (572 oF).  To reach this
> temperature, it typically takes about two minutes of operation.
> During those two minutes, the vehicle produces 60%-80% of its
> pollutants. Of all vehicle trips taken, 98% are within 24 hours of the
> previous trip. Conventional catalytic converters cool down within half
> an hour after the vehicle is turned off, which means for the great
> majority of trips, cold-start pollution raises its ugly specter.

Cheers,
Brian