This is my street car so I need driveability. Which is a better choice. I want the best performance but I don't want to lose low end either. My car is an S5 so the the 6 ports accuation isn't a problem.
Charles

 

Exhaust narrative from Mazdatrix. They have done a lot of testing.

http://www.mazdatrix.com/e1.htm

 

FOr low end power, you want backpressure. SO 2.25. For *** kickin on the highway, you want as little backpressure as possible, so 2.5. I like highway racing, so I went 2.5 to a 3inch muffler. It all depends on what you want to do w/ your car.


When I get my TII, I'm commin over to Austin to cruise around wit ya man!!!

 

sweet rico. Sounds like a plan to me.
I wanna kick some *** all over the place.

Charles

 

Header with 27" primaries collected into a 2.25" pipe, then gradually increase the diameter of the pipe each time you add components (cat, pre-silencers, mufflers, whatever).

 

If Mazdatrix knew that much their car would be setting records by now.

 

Chuck, you should just rip the muffler off of Brian's TII and run same size pipe.

 

Considering the primaries on my header are 2", and its an RB piece, I think that would answer your question. On a turbo car, the story is much different I think.

 

I just sold 2 N1's to a customer with an NA and enough 2.5" piping. I suggested 2.25" but he wanted 2.5". He also purchased a good quality Y pipe. Assuming the welding/fabbing is done well, how do you guys think this will affect its HP over(hopefully!) stock? The only other mod is an intake. One thing I know is it will sond and look great!

 

Also theoretically you could put a choke inline just before the Y pipe and tune the backpressure( and noise). Any objections to that statement?

 

When I say choke I mean butterfly valve and cable, like the one Arospeed manufactures. Sorry for the many posts in a row.

 

So will the 2.25 be better for my street car or should I go all out and do 2.5?
Charles

 

2.25 is better for the low end (in theory) but honestly, if you're keeping them separate, it probably won't make THAT much of a difference than 2.50 on the street. maybe on a dyno, but i doubt if you'll feel the difference on the street.

.02

 

So Evil,
You would go 2.25 from colector to cat, 2.5 from cat to Y and 3 to mufflers? Would that be a good set up?
Charles

 

The 2.25 to 2.5 to 3 would be good for a single exhaust. For a Y with dual exhaust, then I would keep the same diameter before and after the Y.

Using Pi R^2 you can calculate the diameters. With the stats below, you can see that dual 2.25" pipes are nearly 1 sq in larger than a single 3" pipe.

2.00" = 3.14 sq in
2.25" = 3.97 sq in
2.50" = 4.91 sq in
3.00" = 7.07 sq in