i got together with a bunch of guys to talk about engine mods and do some racing and i overheard someone talk about how their exhaust goes from a 4 to a 3 to a 2 in or something like that i didn't get a chance to ask him but can anyone explain?

 

well im guessing first off they he is an idiot if he has that big of a difference in pipe sizes (which is what he was refering to. Now im guessing he was starting the sizes from the muffler. So maybe he has a 4" muffler tip, then a 3" catback exhaust, and then 2" downpipe. That would just be my guess.

 

or they could have been talking about a 4 cyl car header. 4-2-1