EGO and the Smog Pump

[Johnny]

Robert Harris wrote:
> 
> Dah, correct me if I am wrong ( aw go ahead and do it anyway)
> but doesn't the EGO sense total oxygen in the exhaust stream
> and get "happy" around stoic?   If true, then when we shove
> extra oxygen via the smog pump into the exhaust, do we not have
> to shove unburned fuel from a too too rich mixture into the exhaust
> to make shore that the result is stoic at the sensor?  Am I missing
> something here or is the total extra oxygen so low that it doesn't
> make much difference in the fuel consumed??

There are a couple factors involving the smog pump. Firstly, by
injecting air (has O2 in it) into the exhaust manifold right at the
port, it enables any unburnt hydrocarbons to get burned, or reburned
even. Besides cleaning up the exhaust, this post combustion also
increases the temp going into the cat, which helps the reaction that
takes place there. Secondly, at least in the old days, exhaust sniffers
measured hydrocarbons in ppm, so if you add air, you are reducing the
ppm, even though the actual total emissions would stay the same (except
for the reburning effect). This was especially true in the few years of
smog pumps with no cats. Because the O2 part of the injected air gets
used up in the post combustion process, it shouldn't change the output.
I'm not even sure if air pumps are still the rage or not though.

Even the cleanest of piston engine combustions are still pretty dirty
right at the exhaust port. Burning gasoline, even with the best of
combustion chamber designs, and "perfect" injector and spark management,
you still have to massage the exhaust to get it to meet the current
spec. Don't all new US gasoline vehicals have cats? I am no expert on
what's currently out there in production land. Are there any? Not sure
about post combustion enhancers (smog pumps). Seems like most of the
stuff I have worked on had 'em, but I try to stay away from that new
stuff as much as I can.

-j-