krystar

by increasing the flow capability of the exhaust system, you're reducing the exhaust gas's inertia. it loses the ability to properly pulse thru the exhaust piping. it's this pulsing that draws out the last of the exhaust gas and draws in the first of the fresh intake charge. it's called scavenging. when u increase the diameter of the exhaust pipe, u decrease the exhaust pulse's velocity and thereby decreasing the scavenging effect.

Reimu

Since search is down can somebody tell me how much pipe I'll need to replace the cat real quick? I could go out and measure but well.. you know.

krystar

i replaced mine with a 2.25" cherry bomb from autozone. $25 and just weld it in. :P it might sound like *** though. whenever u remove the cat, it changes the exhaust note.

V2Rocket

about 2-1/2 feet should be good...i had my cat replaced with a generic schultz unit so i could pass emissions and it sounds pretty cool now...i loved the old sound but now its got a little more raspiness to the note. also around 3000RPMs it starts to resonate and sounds REALLY cool...if i can find a good camera i might do a video for you guys to hear it lol. car seems a bit peppier too with the old cat gone.

i need to get the weld checked though because cruising in 5th at higher speeds i can hear a little whistle (exhaust leak) that is speed dependent coming from under the console...

Ecos

Well I finally got the new exhaust put on. I went with 3" stainless from the y tube back. Magnaflow xl muffler(14"x9" I think) and a hi-flo Magnaflow cat. I'm pretty happy with it so far. It has some fairly strong resonance to it at right around 3,000rpm but it only lasts 100-200rpm. It also has some raspyness to it at certain points that reminds me of a Honda soupcan muffler but it's not too bad. No resonance at highway cruising speed, it's a bit loud at idle but then my idle is high so I expect it to quiet down once I fix the idle problem (probably a vacuum leak, haven't had time to check). Speaking of idle it was idling at 1,300rpm before the exhaust change and now it's at 1,100.

I didn't have a stock exhaust system on when I made the change so I can't do a direct comparison but it feels faster...I'm guessing I shaved a few tenths off my quarter mile, which surprises me. Something else that surprised me is I expected to lose some torque going with the larger pipe but I swear I actually gained some. This car came with wider than stock tires, from my understanding of it, and you had to try pretty darn hard to get them to break loose. While its still not easy to do I actually managed to chirp them hitting second, which I hadn't done before, and when doing a u-turn out onto the road it broke loose with acceleration that normally wouldn't. So even though the sound isn't as good as I hoped for I'm happy with the performance.

I have a performance meter that I did some readings with the old exhaust and I will try it with the new as soon as I can. I'm not sure if the meter is accurate as far as if it says you're doing a 17.1 quarter mile, if you really are doing it in that time but it is consistent. I tested it on multiple vehicles with multiple launches in the same conditions and it was very accurate. I'm looking forward to seeing what it says.

As I said I didn't have a stock setup before the change so this won't be a direct comparison.

Here is my exhaust saga so far:

Car came with stock exhaust with the cat cut out and straight pipe welded in.

A baffle came loose in the muffler so as a temp fix I had the muffler shop weld in a generic turbo muffler. I gained around .5 seconds in the quarter mile (due to the baffle creating blockage...you could feel the restriction above 4,000rpm)

I will list the meter logs and try to take a sound clip of it with my digital cam. Not sure how the sound will turn out on the cam though, it seems to not capture bass well.

Ecos

Yup it shaved .25 seconds off my quarter mile. It really pulls strong right up to the redline now. Even though the exhaust cost me 20% of the price of the car I'm happy with it. Now to get a wideband O2 welded in.

chrisc

So what happened when I replaced the muffler with a straight pipe & kept the the cat in place? Sound is reasonable (still streetable) & it seems to run good. Passed emissions in Georgia.