I wanted to cut some weight on an A-Stock car but didn't want to spend $$ on some Ti exhaust and/or have to deal with the noise for daily driving. Solution? Cut the stock cat-back just ahead of the split. See highly accurate red line in this picture for cut location:

(Not my picture, but I did add the red line!)

The front section weighs between 8 and 9 lbs when cut where indicated. I added a V-band clamp and a turndown to deflect as much hot exhaust down and away from the body as possible. Total is likely around 10 lbs, for the price of a v-band and a scrap piece to make a turndown. It's Stock legal as it exits behind the driver.

It's great at autocross! 5k+ RPM it's got a nice aggessive note and not as loud as the fancy Ti exhausts. 1-4k is a different story, especially off-throttle. Booming bass penetrates the cabin and generally makes me angry. I drove it around town like this for a short while, it gets old real fast. I live with it to/from autocross, then put the stock mufflers back on at home.

Here's a video from the end of an autocross run, you get a sample of the sound at high rpm and get to hear the boom as the car slows down. This doesn't quite capture how loud the bass is, I think most of the sound might be below the frequency range of the mic. http://www.youtube.com/watch?v=joIsckGVnT0&fmt=18

Entire autocross run: http://www.youtube.com/watch?v=J01LecPo3gA&fmt=18 (had mic WAY too close to Modifry shift beeper, sorry!)

The old butt-dyno says there's a considerable loss of torque below 4k rpm. I'm never below 5 for autocross so I don't care!

Just slip on the 4 exhaust hangers* and bolt on the rear section for normal volume levels for daily driving. If you're really anal about weight you could cut it further upstream and either try without the turndown or install a really short one with a slip-fit connection.

* I make this sound easier than it is, it's a pain in the butt! I use a box to support one muffler close while muscling the other into place and connecting the hangers. It takes about 5-10 minutes total to change out the back section.

 

I should add that the single hanger left on the short exhaust is stiff enough to keep it from hitting anything. It can move around with the flexibility of the joint in front of the cat, but it's not that extreme.

 

[QUOTE=captain_pants,Jul 27 2008, 12:26 PM] The old butt-dyno says there's a considerable loss of torque below 4k rpm.

 

I did kinda the same thing 2 years ago except I added a DC universal. It was def heavier than urs and sounded a lot like an Invidia.

 

Corey,

This is extremely interesting, as I think everyone is on the same boat for AS. Do you just slip back on the two OE mufflers, with some clamps holding it together, or do you have a new OE exhaust entirely?

I'd like to see if it's livable, as my Espelir exhaust was just drone mania . Does your "boom bass" happen at 3-4k rpm?

Great post, and post pics

 

Kurt, I am thinking of doing something similar, but getting a single Borla muffler mounted where the right side stock muffler is. Maybe we could both get ours done at the same place. You're in Fresno?

 

I have done this as well, but no turn down, I just cut it in the same place with a hack saw. It is VERY annoying at low RPMS as mentioned, I don't drive it much on the street so it's not THAT bad, there is also some resonance around 3k rpm that is getting old.

Def an easy mod for a LOT of weight savings for autocrossers. I had also considered cutting before the resonator, and running a straight pipe back to an OTS borla or something, but I don't think it would be worth it.

 

I think I will serious consider this. I love the sound of the WS2 system that came on my car when I bought it... but damn that system is heavy.

If I can find a cheap stock system I think I will be doing this.

For the OP who puts the stock mufflers back on... did you just make a sleeve and band clamp it on?

 

[QUOTE=Orthonormal,Aug 4 2008, 08:03 AM] Kurt, I am thinking of doing something similar, but getting a single Borla muffler mounted where the right side stock muffler is.

 

V-band is a 2.5" Vibrant. There's nothing special about the V-band, I just got a deal on it.

My plan is to eventually run a single 2.5" muffler on the passenger side for street use, but this was done in a rush before driving to the Milwaukee Tour event. Didn't want to risk having drone in a 12-hour (each way) drive! My inspiration came from this: https://www.s2ki.com/forums/index.php?showtopic=499893
I wanted an even lighter option for autocross.

Downturn installed:








Stock exhaust rear half. This is 40 lbs!




Stock hanger, a little difficult to pull rubber hanger off without tools:


Shortened version, MUCH easier to get on and off. Haven't had any hangers slip off in about 1600 miles of driving.


Reinstalling the rear section, put a box or something under one side to get it close to the right height:


Install hangers on side without box, can go from below or through wheel well (don't need to remove tire if car is jacked up):


Then attach remaining hangers:


If you look close you can see the male and female ends of Vibrant V-band:


Simply line them up and it slots together very nicely:


Clamp doesn't need much torque at all. Notice bend in T-bolt in below picture, I overtightened it the first time. That's a cheap 8.4V drill with minimal torque - maybe 10-15 lb-ft.


The finished product: