what would be the best size exhaust for a mosty stock 1988 rx7 with a 13b?

 

2 1/2 or 3" works great. But what you use for cats and muffs is going to be another factor.

 

when I was getting my exhaust done on my car (unfortunatly not a rx7) my friend who was putting it on said that you don't need huge size pipes, the 2 1/4 size pipes that he put on my car I saw him put the same pipes on a huge truck, and i"m talking about the one that's like 30" long and have a huge bed in it. but then again, it might matter if you're blowing tones of boost through it, that's still something I have to learn much about

 

For a normally aspirated car, I would say no bigger than 2.5". For a turbo car, 3" should be fine, maybe a tiny bit bigger if you're going to be running a lot of boost. I'm going with a straight through 3" exhaust for my TurboII.

 

yeah i was thinking 2 1/2 i work in an automotive machine shop i use to have a mk2 vw golf that i put a turbo on i had 3" all the way back bigger the better on a turbo u do not need back presure after the turob no matter what any one tells u bigger is always better on a turbo

 

shoot, i have a camaro with a 350 in it and a 3" main pipe is plenty. i plan on going 3" all the way with my TII. instead of a pre-cat/silencer then y-pipe, i was just gonna get a straight through Magnaflow muffler that's single in/dual out...kinda like two birds with one stone. then get some Magnaflows out back.

 

For a mostly stock 88 NA go with 2.5"
For a turbocharged go with 3" or 3.5" if it's lots of power (like someone said before).

What is more important though, is that the piping you get has MANDREL BENDS and that the joints are smooth and nice. A pipe with X diameter and mandrel bends will work better than a pipe with a slightly larger diameter and non-mandrel bends.

It's all about EGV (exhasut gas velocity). The faster you can get it out, the more power you will make, and the more torque you will make.

Get 2.5" with Mandrel Bends... full system, no 1/2 way back crap.