I was rescently discussing eahausts with my friend. he says he will always have his stock, because if you put on a bigger exhaust, the air coming out will cool down in the pipe and therefor slow down, causing the engine to work harder to push it out. however ive been always thinking that 2"-2.5" is the ideal size. anyway i just wanted to know if hes right or hes an idiot. id also like to know what the ideal size for an exhaust is.

if this varies car to car id like to know what ideal size would be for a 98-00 gsr teg.

 

if your exhaust is too big, then you will lose back pressure therefore you lose hp. i have a 2.5 catback on my ls, runs great!

 

yeah i know that. bigger exhaust (before it gets too big) means higher hp but less torque right? and i was thinking something like 2.25 was perfect for a teg. i jsut wanted to know if it would be better or worse to have 2-2.5 exhaust or stock

 

I have 2.5in on my GSR and it works great. The only time you would want to go bigger then that would probably be turbo.

 

the bigger the better
why do u think running unbolted exhaust gains

only the header area needs back pressure
thats why it s called tuned headers!

 

I don't know about the whole exhaust-cooling-down-therefore-slowing-down thing. I think he kind of pulled that out of his ***. But it is true, a bigger pipe does mean slower moving air (for much simpler geometric reasons). So if you go too big, the air will move too slow to assist with scavenging of cylinders (I don't understand that part enough to explain in further detail).

Either way, you want the exhaust to move fast, so you want a smaller pipe. However, a smaller pipe and fast moving exhaust increase back pressure, which you don't want (ever). So the key is to find the right size exhaust that will yield the highest exhasut velocity with the lowest backpressure, which I understand is around 2.25" for a car like a GSR. This number will change depending on how much air is being pushed out of the engine (how much power it's making).