Difference between a muffler and a catalytic converter

A muffler makes the car quiet, the cat makes the exhaust clean. Cars built after 1974 originally had both, but it's legal to run with no muffler as long as the car isn't too loud. The cat is required, you can't pass emissions without one. Some people will remove the cat, if they live in a county without emissions testing, but that is illegal.

If you have a car with no catalytic converter, and the muffler goes bad, sure you could put a cat on instead. They're more expensive, and louder, but that would get you legal. Actually, the cat is supposed to be mounted closer to the engine, where there is more exhaust heat to burn off exhaust crud.

I suppose if you wanted to, you could run two catalytic converters. That would greatly restrict your exhaust and cut down on horsepower, probably reduce fuel economy as well. Probably wouldn't help emissions, either.

hey are two totally different things,each with it's own 
seperate purpose. You could put 2 converters on
,but I don't know why you would want to,.....also doing this will give you a ton of back pressure causing your engine to work harder just to keep running

there two different parts. two different things you have to buy or get replaced. catalytic converter may make a rattle noise that gets loud. kinda like if you were to put a screw in a tin can and shake it around. the muffler will make your car loud if you dont have one lol.. two can be expensive repairs!!