Purpose of dump pipe

[Black1986Beast]

Hey, I'm just wondering if I'm thinking right..
If I got a 3'' dump pipe, would the purpose of it be to connect to the 3''down pipe and the cat??
If so, is it open all the time? or can it only be opened whenever YOU want?
Also if this is how it works, is it legal to have on? like for inspection?
Thanks

 

[Fred 86 GN]

A 3" dump pipe, like a 3" test pipe, will connect the downpipe (which comes from the exhaust side of the turbo) to you cat-back exhaust. They replace the catalytic converter. Neither will pass an inspection, unless you weld the catalytic converter's clam-shells to the test pipe.

A dump pipe has a "Y" in it and a cap on the blind end of the "Y". You unbolt the cap to "dump" the exhaust and bypass the mufflers and tailpipes.

 

[XLR8]

My dump pipe is in place of the cat and in no way would pass a visual emissions inspection. The dump is only open when I want to dump the exhast before it goes through the complete system. I believe you can run both a dump and cat with the Terry Houston "Jersey" style down pipe. Of course you can not run leaded race gas through the cat.