This stuff is exhausting...

[JohnW8]

I'm driving a former spec miata in ITA and am looking to make improvements to the exhaust. I've added a racing beat header, which isn't ideal but it was sitting on the shelf in the garage. The car has the Springfield Dyno exhaust which is very popular in the Spec Miata class but it's dang loud and lacking in low end torque. What would be a good source for info regarding a better exhaust system for a Miata that helps low end torque, still breathes up top and quiets things down a bit to eliminate sound violation worry at some tracks?

Keep in mind, I'm not made of money.

[Greg Gauper]

I happen to be a very big fan of the Borla Sportsman XR1 racing muffler.
I run one on my H-Prod. Doesn't seem to hurt the power and it is very quiet.
I'm typically 85db to less than 90db at most tracks.
They run around $141

http://www.borla.com/products/produc...?cat=5&type=72

[Andy Bettencourt]

I'm driving a former spec miata in ITA and am looking to make improvements to the exhaust. I've added a racing beat header, which isn't ideal but it was sitting on the shelf in the garage. The car has the Springfield Dyno exhaust which is very popular in the Spec Miata class but it's dang loud and lacking in low end torque. What would be a good source for info regarding a better exhaust system for a Miata that helps low end torque, still breathes up top and quiets things down a bit to eliminate sound violation worry at some tracks?

Keep in mind, I'm not made of money.

You are describing what we have done over the 4 or so versions of my system. I get to pay for the development, our customers benefit!

[JohnW8]

You are describing what we have done over the 4 or so versions of my system. I get to pay for the development, our customers benefit!

Andy, your website doesn't have much to say regarding exhaust.

[Andy Bettencourt]

Andy, your website doesn't have much to say regarding exhaust.

True. All this stuff is custom one off's effectively built and tuned on the dyno. If you want more info, PM me. Unfortunately, the parts aren't real cheap.

[FLATKITTY]

There is no hard & fast rule about the perfect performance muffler for every engine or exhaust system. However, years ago, I became a Borla convert.

#1 ... Many moons ago, we did a dyno test on a customer's ITS 240SX KA24DE engine w/open exhaust (cuz that's how he planned on running it). After the final test, we installed a Borla exhaust (sans pre-muffler). No HP loss, but an immediate 12 ft/lb torque increase.

#2 ... My own street Mustang GT came w/a Magnaflow exhaust system that was straining to push 6500 RPM. With nothing more than Borla system, the engine immediately pulled to 7000 RPM.

#3 ... And my newly built ITS car has 2 of the Borla XR-1 mufflers tho no before/after test was made. I chose them only cuz I never felt cheated buying Borlas.

And I have never seen Borla not finish well (if not 1st OA) in any muffler test article.

With all that said, it does surprise me a bit that due to probably more dyno testing than any other sports car engine out there, that THE muffler has not been determined for the Miata.

Andy, you sound like a person who has spent a fair amount of time under the hood of the Miata ... is there not THE perfect muffler for the Miata?

[lateapex911]

The issue isn't the muffler. It's the size of the primaries, the bends, the length, The collector. 2 into 2 into 1? 4 into 1? Shape of the collector, and length. Size of the pipe after that...length of the pipe.
Then there's reversion stuff, and crossover balances, etc etc etc.
Oh, and the muffler.

This stuff depends on other factors as well. The porting and gasket work. The intake. Etc etc. And, of course, the tuning via the ECu.
It's all interrelated, which is why you usually find the guys who have done it, and done it again, are pretty quiet about "the answer". One, because they spent $$$ (I did three complete systems on my car searching for better answers, and one header is unlike any I've ever heard of, a complete custom unit), and two, because there IS no ONE answer....it's all dependent on many other factors.