I hope this hasn't been discussed a billion times, and I did search for the answer and I read the FAQS,

I have an extra OE exhaust and wanted to mod it for Autocross (AS). I don't expect to gain any power by doing this but I'd also like to avoid losing any. I mostly want to lose reduce the mass of the system.

Has anyone played with this before? I feel like removing half and running a single with a stock muffler would be too restrictive due to the reduction in volume, while just removing the mufflers and running two straight pipes may be too loud.

I don't daily the car, and have no problem swapping for the stock system for race days, am I wasting my time?

 

I removed my stock exhaust and had a muffler shop build me a single. They just built a single pipe from the Y pipe back to a Magnaflow muffler. No 8" coffee can just a black painted 3" tip.

Net result in weight was 48 lbs lighter. The sound is mellow and not too loud.

My butt-dyno tells me there's a bit more hp but weight was my primary objective.

It cost me $400.00.

SOLO

 

Which Magnaflow did you use? I have a 14# single exhaust with a muffler that doesn't do a good job of muffling. "Mellow" is not an adjective I would use to describe it.

 

I will have to take a photo, but I made a "prototype" single exhaust using stock exhaust parts. I call it a prototype because it was an experiment and has some cosmetically unappealing welds. I plan to make another one with a cleaner execution.

It is the stock exhaust from cat back to just in front of the Y including the stock resonator. I took another stock resonator and used it for a muffler suspended from the rear most hanger. To this a stock polished tip was attached. I really like the sound and use it for daily driving. It weighs less than 20 lbs. Stock exhaust weighs 54 lbs, so a nice weight savings greater than 34 lbs.

This setup cost me about $30. I gave a $20 Starbucks card to the person that donated their exhaust so I could make it. The other $10 covered the few exhaust pieces I bought at the auto parts store to join it together.

You can hear it okay in this video...
Autocross Video

Here's a video from when I made it. It is mostly passes in first and second gear. There are a couple of other cars that pass by for comparison.

Home Made Exhaust Sound Clip

 

OP...sounds like you're wasting your time.

 

You can just cut the mufflers for weight, autocross has no specific noise rules. It will be ridiculously load. If you need to drive it to/from the track, put flanges on the ends of the pipes and the mufflers.

Or just get/make a light single with a decent muffler you never have to change.

 

Depends on where you run. Our local region enforces noise levels. I would say about half of the regions I've run in have some sort of noise requirement.

 

Exactly: no specific noise rules. Most regions I've heard of with rules simply specify "not too loud." I doubt you will ever run into a sound meter.

Either way, reading the rules and checking with your local region should obviously be part of the measure twice, cut once philosophy.

 

SD Nat. Tour has strict restrictions on db levels, I've seen the meters out.

 

Wanna meet our sound meter? Calibrated and all.