I originally posted this in the NA forum, but later thought you guys in the Tuning scene would provide better input or have experience with this.

I'm preparing an exhaust setup where both quietness and performace are of great concern (obviously not at the same time). Because of this I want to utilize an exhaust cutout to switch from an open setup to a regular muffler setup. I'll be using an input to my eCtune to switch between maps when the cutout is open and closed.

The setup will consist of 2.5" mandrel bent SS tubing coming off of a 2.5" header collector, using one Vibrant 18" resonator (maybe two resonators if I need to quiet it down more), and one Vibrant muffler. However, space and ground clearance IS a concern when determining where to install the cutout.

Having the cutout directly off the collector might pose a problem with the front sway bar, or conversely with ground clearance. My other option is to mount it towards the rear after the resonator(s) but before the muffler. This would give me more room to install the cutout, and maybe even weld an angle onto it to point it to the ground, but after two 45 degree bends in the exhaust system. Would there be a dramatic difference in exhaust flow between having the cutout right off the collector like an open header versus having it towards the rear, after the resonator but before the muffler?

Simply, if I HAD to put the cutout towards the rear, would it not be worth using at all?

 

With it being NA, the gains you'll see between full exhaust and the cutout will be minimal regardless of placement. But that's what NA is all about, lots of minimal gains.

As far as amounts of restriction, you won't see too much more if the cutout is towards the rear if you don't have a cat for it to go though. The muffler will be the worst restriction, esp if its chaimbered. I think it was Jeff Evans who tested a boosted ITR with stock exhaust: in the 300 range, it picked up 20whp from unbolting the stock axle-back w/o any extra tuning. My experience is that a few feet of piping & straight-through resonator is worth it just for the noise. A turbo exhaust easily 50% louder w/o the extra piping & resonator.


Here is my custom cutout, basicly a v.powerful motor that opens a 65mm throttle body via cable; turbo-back 3" + resonator, stock muffler/piping after the cutout. The area I have it at has about 1" less to work with vertically. It still doesn't bang anything, and the resonator hangs down further. However you may even want to consider putting your cutout right before the shift lever, since yours will have that chunky motor hanging off the side.

http://www.youtube.com/watch?v=1_2RlSZoplw

 

Thanks for the info man! Joseph Davis (my tuner) actually referred me to your cutout, and I've read through several of your threads.

I'm trying to complete this N/A setup to prove a point with a few friends, but I'll be boosting as soon as I get my final all-motor numbers.

That being said, I'm setting up this exhaust to work with both setups. The Vibrant muffler I'll be using is a straight through design, so hopefully it won't be too restrictive. Like you said, I'm expecting to utilize some sort of cutout to get every little bit from the N/A setup, and I know it will help much more with the FI setup.

I also have a stock TB lying around that I'm considering using after seeing your setup. How did you mount the TB to the Y pipe since the TB is aluminum?

 

As far as the vibrant mufflers, they seem to flow well and keep the noise down. Even better is the fact that they look almost "stock" flat black and small tip. I had a 2.5 inch mandrel bent exhaust with 22 inch magnaflow resonator/no cat on my previous 1.8L build. Sound was nice and not too loud/raspy. Current setup is a 2.0L GSR motor, 3 inch KTeller piping with 2 12 inch resonators from SMSP to a 3 inch vibrant flat black muffler. Sounds nice, deep and not super loud..