What is the deal with people talking about y-pipes with no catyltic converters, do the y-pipes themselves have like catyltic converters built into them?? I dont really understand... like what is the difference between a free-flowing y-pipe and just a standard one, arent they just a pipe?

 

I'm guessing that what you are referring to are the people who remove the catalytic converter(s) and put a piece of pipe in it's place. And it is all after where the ypipe exits (except on the factory dual cat cars).

 

The stock Y-pipe is tiny, heavy, and crush bent.

Aftermarket ones will be much larger diameter, 16 gauge steel, and completely mandrel bent. Both can have accomidations for the cats if you want them there. Then all you have to do is buy a free flowing cat, weld it on, and call it a day.

 

onebiky nailed it on the head. The cat is what connects the y-pipe to the rest of the exhaust piping. Some people replace that with a peice of pipe while others go the single or dual cat route.