So recently I've been reading up on the different modifications for the exhaust but I'm trying to clarify some terms I've been coming across such as y-pipe, x-pipe, test pipes, mid pipes, straight pipes, etc. I've attached a picture of an oem exhaust of a g37 with colored boxes around each section of the exhaust. Can someone that's familiar with the terminology fill me in?

Thanks!

 

From bottom to top, you've got the Y-pipe "red box" (which the two ends would connect to the factory catalytic convertors (which can be replaced w/ High Flow Cats aka HFCs, or Test Pipes), you then go up to the mid pipe which is the "blue & yellow box" and included mid pipe resonator chambers, then you go to the final pipes "green box" leading to the mufflers and tail pipe tips which aren't pictured.

Custom setups or cat-back exhaust eliminate the Y-pipe, and use X pipes or sometimes H-pipes to tune the exhaust note while still keeping a dual exhaust, and some run side by side w/ no crossing over.

 

X, Y, H pipe is referencing the exhaust piping design. Each 'crosses' the exhaust gasses differently for different sound. This is the top of the red box in your picture.

Straight pipes are just that...nothing but pipe. from headers back the the tip. No mufflers, Cats, or resonators. Don't do this. Your neighbors will burn your house down.

Test pipes and High flow cats are replacements for the factory cats that allow more of a free flow of the gasses. Test pipes will generally result in more power but be louder and smell a bit more.

In reference to your picture: Green is the end of your exhaust where your mufflers would attach. Yellow is your resonators. Blue I guess would be your mid pipe. Red is where your Y, X, or H setup would be. Further up from that is where your factory cats are located; and where you would install test pipes or high flow cats (HFC). Next is your headers which connect to the block.

 

Thank you for the informative replies!