By-pass pipe instead of cat?
 

While tearing down my '81 engine (930/16 US version) I discovered that I have what I think is a by-pass pipe instead of a cat in my exhaust. Right? I didn't pay much attention to the exhaust since I have bought the cat a year ago and always assumed the car would have a cat. All the CIS components are there including the O2 sensor, and the system is perfectly working in closed loop mode (term?).

As a European I'm not familiar with US regulations. I have always read about the strict US smog tests (visual and measurement) and I'm now wondering how the car may have passed these tests. The by-pass and the bolts are such rusted that it must have been there at least the last ten years. The car was last registered in Wisconsin, and I have a bill that shows the O2 sensor has been changed in 2011.

Any thoughts???

Thanks, Manfred

http://forums.pelicanparts.com/uploa...1364496546.jpg

Smog tests are a state-by-state issue. The rules in each state are different.

Many/most states no longer smog test a car that old.

that is a bypass. in Europe they had a premuffler in that spot; it was a straight through design but had an outer tube and perforated inner tube and reduced the sound a little (probably tuned the sound more than reduced it). only some states have smog testing, like California. most in the South don't.