Variable Restrictiveness Exhaust

[William T Wilson]

Okay, this seems to be the best place to talk about random, goofy car mods
that just might work. :}

Suppose I have a car that I want to pass emissions, but I also want it to
gogood.  Why couldn't I make some sort of cat-bypass system which would
allow the exhaust to flow openly at high revs, but flow through the cat at
more "normal" RPM?  Maybe a solenoid-activated valve attached to the tach,
or perhaps just a flap on a spring like at the top of a big-diesel
smokestack.