At 2:50 AM -0600 6/14/96, Tony Robinson wrote:
> Although, in my opinion, a smog pump, which actually just pumps fresh
>air into the exhaust is a cruel hoax by auto manufacturers. It reduces
>the % of CO and hydrocarbons by merely pumping in additional quantities of
>raw air. Thus, fooling test equipment into thinking that solid emissions
>comprize a smaller % of the total exhaust gases.
Please, this is not true. Think about it.
Your engine displaces something like 100 cubic inches, which means it pumps
roughly that volume of air every two revolutions (more, if your manifolds
are well tuned...). Your smog pump spins at about the same speed, and
displaces two or three cubic inches. So, it pumps maybe 1/20th of the air
the engine does. How could it possibly dilute anything enough to matter?
The thing it does do is dump fresh oxygen into the hot exhaust gas. This
causes much of the partially combusted, but still toasty, HC and CO to
finish oxidizing itself into relatively harmless carbon dioxide and water.
If there's a converter downstream, it feeds the converter the oxygen it
needs to do even more of the job.
Simple and effective, actually. And it doesn't even affect the performance
of the car, other than to swipe a HP or two at high speed. More than you
can say about leaned-out carbs and mid-70's ignition timing...
-john
John Wroclawski
jtw@lcs.mit.edu
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