<VV> Catalytic Converter for Corvair

[Craig Nicol]

Bill said:
<big snip>
I brought my car to an exhuast specialist, who was a
really nice guy.  He looked my car over and mentioned
that all horizontally opposed engines had a sort of
grumble to the exhaust.

He tried a resonator tip on the end of the pipe, but
it didn't make any difference.   He told me that the
only thing that would really make a difference would
be a catalytic converter.  those thing are supposed
really quiet down the exhuast, but he wanted around
$250. to custom-install one in my car.  He said there
is no reason why it shouldn't work.

Meanwhile, I saw universal, mini-catalytic converters
for $59.00 plus  shipping.  I was willing to try that
just to see what would happen.  The unit is very
small, only 4" diameter at its thickest, and around
10" long.  

I kept the stock system but mounted the converter
behind the muffler, replacing the tailpipe.  The
exhuast now dumps behind the car instead of out the
side.  The first thing I noticed was that the exahust
was much quieter.  The second thing I noticed was that
the exhaust no longer stunk with that pre-emission
smell, but smelled more like a modern car.  It's a
much cleaner smell.

Only time will tell if it holds up, but I'll keep
everyone in the loop as the miles roll up, G-d
willing.

Assuming that CO is reduced with the converter, I
expect that it will be safe even with the windows
rolled up.  My digital CO monitor inside the car will
let me know levels in the interior as I back the car
out of the garage and drive at different speeds in
different weather conditions.

In addition, the large diameter exhaust outlet (2")
looks cool, even with no tip on it yet.  I'll try to
get a picture of it when I have the chance...Bill
Hershkowitz 69 Monza Coupe 110 PG <unsnip>

Craig opines:
The typical catalytic converter converts CO and HC to CO2 and H20, assuming
the components are fed from an engine that's running neither rich nor lean
but in exact 14.8:1 ratio of fuel to air.  Corvairs are not calibrated to
run at this stoichiometric ratio.  Usually, they are relatively rich.  This
puts the cat into the business of burning the excess HC, which is what
creates the "rotten egg" smell (H2SO4?).  After a steady diet of excessive
HC, the catalyst's substrate will melt, fuse, and clog the exhaust.  There's
also a fire hazard, especially when they're fed excess HC, which is why cats
have a heat shield on the upper side. Excessive backpressure can burn
exhaust valves too. 

'68 and '69 smog engines might have the best chance of all years for this to
work 'cause the carburetors have more accurate mixture control.  Since
you're a pioneer, keep us posted!  The only other Corvair I've heard of with
a cat has a 4.3V6!
Craig Nicol

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