Autocross exhaust questions
 

1. For those that have run turndowns, have they attached them directly after the last cat, deleting the entire pipe before the muffler? If not, why not? I would think that would be the lightest option possible.

2. How can I keep my exhausts swappable? The exhaust shop I went to doesn't have a flange that matches up to the last cat. I've tried to find a second OEM pipe to cut up, but new they run $125+shipping, mazmart has none, nor are there any junkyards close enough to me to make it cost effective. Is it possible/legal to cut off the cat flange and replace it with a generic one?

Thanks.

Zach,

If you are going to the Marina event next weekend, check out my exhaust. I have it flanged so that I can swap out mufflers or put a down turn on if you want.

One consideration to keep in mind, with a turn-down ending directly after the final cat, there will be a substantial increase in interior NVH.

I ended up buying a Mazdaspeed Version 2 exhaust for street use, and used my stock catback pipe to make a light-weight 8.1lbs race exhaust that exits behind the car. It's too loud for daily driving, but just right for competition purposes.

I bought mine for $40 (the entire aft-cat section to the tips) from a kid on Craig's List who had just purchased a high-dollar exhaust. Had less than 1000 miles on it. I hung it in the garage and cut up my old one to do the single exit Borla setup. Took about two weeks of watching till it came up for sale.

Btw, if you're looking for a universal 2.5" mandrel bent turn-down, Summit Racing sells them:

https://static.summitracing.com/glob...10410flt_w.jpg

I don't have the part #'s handy, but you should be able to make one of those work, or take it to an exhaust shop and they could adjust the flange to make it match up with the flange on the cat.

Zach, the turn down will work for our local events, but won't pass sound at SD. But, if you cut your midpipe at the factory attachment to the muffler, it is easy enough to weld flanges on both sides, making the muffler easily removeable...about 15 minutes on/off.

I told Bryan that, if you want, I can give you the parts list for the single exit that I copied off of Jason. You would still have to find a mid pipe, but like kjchristopher said, they do come up fairly often, on craigslist or mazmart. Ultimately, that is the most convenient solution, imho.

Glen, is Matt going to install the exhaust I sold him? If not, maybe he'd be willing to sell it to Zach...

Marina as in Marina, CA? Did I see you guys at the Jan. AutoX? There were 2 other 8's there and I meant to stop by and say hello. You guys were in BS, I was in OSP

Thanks for all the responses.

Glen, I think I'll be at Marina, so will take a look at yours then. Thanks for the offer.

Mike, the plan is to do an Isley-style exhaust for SD and daily driving, but I also want the turndown for nats (there aren't any sound restrictions at Lincoln, are there?) I also want to keep the stock exhaust for when I sell the car. Three exhausts should be enough, right? :)

Ross_Dawg, I wasn't at Marina in January, have only been doing SFR SCCA events so far this year. But, the next SFR event is at Marina next Sunday.

If I can't find a pipe, I might just cut the original pipe, insert flanges and have that be the swap point for all 3. Then I wouldn't need a second pipe. The question is where to cut it. Near the cat for added lightness, but extra loudness? Or near the muffler for easier swapping at the expense of about, what, 5 pounds for the pipe? Or somewhere in the middle if I can't decide? :)

The design of the single exit "Isley" exhaust is going to dictate where you cut the mid pipe and weld in the flange...

That's exactly what I did. Put in a flange, and then you can swap out to anything with a flange on it. I put min closer to the back for ease of swapping. I don't know if the extra 3-5 lbs of pipe makes much of a difference.

swapping is a PITA as is the noise, I'll take the extra few pounds over the bother

https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/latest-teamrx8-custom-catback-dual-exhaust-139662/

they make electric cut-outs (turndowns) too. You can flip the switch and it closes the normal exhaust and exits the pipe thats not connected. That way you can have it loud whenever you want. That is what I'm buying. It is around $175. I can't find the demensions of 2004 Rx8 6spd exhaust for this cut-out. What are they? Also where did you go to get this installed? It's illegal and I don't know if locals will do it.

And whats the point with that? it will even be little heavier then not having that switch.

I'm guessing he's mistaken the purpose of the mod.

I say the electric one is a good choice because that way it is legal for inspections and you can have your car quiet or loud.

except that the point of the conversation is how to lose weight off the exhaust while still coming in under the sound limits at autocross events. :) keeping the stock 37lb muffler on the car and installing extra stuff to simply make it louder isn't really a benefit in this context.

The "Isley" package is the way to go. It's loud enough to remind you why you bought a rotary in the first place, significantly reduces weight, and is just under the db limit. IIRC, I was in the low 90's at Dixie last year and we ranged from 87 - 89 at Nats.