Exhaust Size

[ratherbriding99]

Well, this next weekend i'm going to be building exhaust for my 420a sebring. I'm just wondering what size tubing you guys recommend. I'm running the stock exhaust manifold and i have a borla can that has a 2 1/4 inlet. But i'm putting a flange on the exhaust so i can put a different can or straight pipe on if i want. I do plan on putting a header on in the spring. I'm also getting rid of the cat.

 

[spdtckts]

Well, this next weekend i'm going to be building exhaust for my 420a sebring. I'm just wondering what size tubing you guys recommend. I'm running the stock exhaust manifold and i have a borla can that has a 2 1/4 inlet. But i'm putting a flange on the exhaust so i can put a different can or straight pipe on if i want. I do plan on putting a header on in the spring. I'm also getting rid of the cat.

if you keep it reletivly close to 2.5-3 inch you shuldnt loose your back pressure but if you go to much bigger you will loose your back pressure and some power

 

[VelocitàPaola]

For a 2.0L N/A car, 2.5" is a good diameter for the exhaust pipes. Turbo guys usually bump it up to 3", but rarely bigger than that.

 

[ratherbriding99]

well i got it all done, after about 20 hours of work on it . I put 2 1/4 on it because the shop didn't have 2 1/2 at the time. I never thought the cat would make that much difference in sound. Its significantly louder now, and sounds a lot more "ricey". It does feel a little faster, but i needed to have it on the dyno because the sound is so distracting. I'll put a video on here later this week for reference.

 

[BigRand]

Worse comes to worst, just spring for a high flow cat. I'm even thinking about putting my old 2.5" one back on my car to pass inspection.

 

[ratherbriding99]

thats what i was thinking about doing. Do you have or know anybody who has an o2 simulator on their car. I made the one with the 3 50 ohm resistors on the heater wires and a 1 micro farad capacitor and 1 mega ohm resistor on the signal wires, although the tech article on here shows two different orders for the capacitor and little resistor. Regardless my cel came back on today. I have about 40 miles on the eliminator.

 

[xXaTaXx]

if you keep it reletivly close to 2.5-3 inch you shuldnt loose your back pressure but if you go to much bigger you will loose your back pressure and some power

Backpressure isn't what causes the loss in power (I assume you mean torque?), It's the loss of velocity and temperature of the gasses in the pipe which reduces scavenging. I think its something like, once you install a larger exhaust on a n/t (w/o turbo) car, your effective RPM range for scavenging slopes into a higher RPM range, this take power away from your low-rpm range, hence the noticible loss of power. Backpressure is always your enemy, in ANY case.
--
Chris