Air Pumps

[George Beston <gbeston@domain.elided>]

In alfa-digest V8#592, Joe Elliot wrote "I don't understand why you'd have
an air pump on a car with no cat".  What follows is my understanding of what
the air pump was all about, which no doubt someone with greater insights
than I have could probably elaborate on.

Air pumps were commonly used in the pre-catalytic converter (also
pre-unleaded gas) era as part of a strategy to minimize emissions.
Typically, the engine was set up to run well on the "rich" side of
stoichiometric which contributed to  minimizing NOx emissions. Air from the
air pump was dumped into the exhaust gasses (at the manifold, in Alfa's
case) to burn off the excess fuel in order to achieve acceptably low
unburned hydrocarbon and carbon monoxide emissions.

Obviously, this approach wasn't particularly efficient.  In Alfas, it
resulted in poor fuel economy and some red-hot exhaust manifolds.  My
Alfetta had the drive belt for the air pump removed from day one, and the
air pump came out and stayed out the first time the SPICA FI oil filter
needed changing.

George Beston
Alfetta
Spider Jr.

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