Loud Miata

[jimalley]

Looking for cure for a very loud ITA Miata. This car is noticably louder than any other Miata on the track and depending on conditions I have had sound readings from the high 90's to 104. I installed a new muffler between the last two events without any noticable difference.

We have changed the muffler location to see if this would make a difference without any noticable effect.

Looking for a non-restrictive muffler that will quiet this car down:shrug:

[Greg Amy]

Jim, I'm a big proponent of quieting race cars down. It will improve our health and community relations, and if you do it well it won't even hurt performance.

What mufflers are you using now? I'm assuming you're running one of those annoying Spec Miata exhaust that the pack is so fond of? I've gotten to the point with those cars that I'd prefer to listen to Jake's rotary engine than the SM race...

Anyway, on both the ITA NX and the ITB Swift I ran a single Dynomax Ultra Flo with a center dump, and both cars were the most quiet in the pack. It turns it from an annoying, raspy sound into something much more mellow:

http://www.summitracing.com/parts/WLK-17230/


BTW, if you want to try that part I linked to above, 2.5" UltraFlo muffler, I have a brandy-new one in my garage. Try it, see if it works, and if so make me an offer. I tried to use that on the STL Integra, but the floor pan/tunnel on the 'Teg is too small and the muffler sat too low to the ground. However, I seem to recall that the Miata tunnel is better.

What I went with for the Integra was a pair of these in series:

http://www.summitracing.com/parts/WLK-24236/

I cannot yet offer feedback, but the sound level is similar (at near-idle speeds) as the UltraFlo. We've used that muffler successfully on the Integra (another raspy annoying-sounding engine) coupled to one of these in series:

http://www.summitracing.com/parts/MPE-10416/

...and we passed sound at NHMS. We were also told that it was the quietest ITS car out there (at the Road America Runoffs folks on the front straight said they could barely hear the car...) I also have one of those Magnaflow (used, but in good condition) that I took off the Integra that you're welcome to try.

In summary, my suggestion would be that if you have the space under there to try the UltraFlo first with a SM tailpipe exit under the rear. Then, if that doesn't work well enough (though I think it will) you can try adding in one of the smaller resonators like the Magnaflow. Give me a ring and I can get these parts to you for a tryout.

GA

[jimalley]

Thanks Greg. PM sent.

[ddewhurst]

I'm assuming you're running one of those annoying Spec Miata exhaust that the pack is so fond of? I've gotten to the point with those cars that I'd prefer to listen to Jake's rotary engine than the SM race...


Come on Greg, no one likes to listen to a rotary. My ITA rotary had the ISC Racing exhaust & it was a hell of a lot more annoying than my SD exhaust on my Spec Miata.

Or is it the competition of the Spec Miata's that is anoying?;)

[Andy Bettencourt]

Jim,

We did mine from scratch, made it quieter and found area under the curve. Call Nick.

[Matt93SE]

I use a single one of these on my 240SX with 2.5" pipe from the header back:
http://www.summitracing.com/parts/MOR-94050/

It's not as loud as the SM guys, and I get a lot of compliments on how the car sounds vs. the rest of the stuff out there. I don't know what it sounds like outside the car (since I'm always driving), but it sounds like a throaty SM to me from the inside.
I'm also usually 3-5dB quieter than the SM guys when I look at sound reading charts. 88-90dB when they're 91-95.

[jimalley]

Thanks everyone for the input and suggestions. I installed an Ultra Flo on the car tonight and I am very happy with the results:happy204:

The sound control personnel will be happy as well:026:

[StephenB]

Thread hijack :) Figured I wouldn't start an entire new thread for an exhaust question related to sound...

I am contemplating between the Borla XR-1 oval or Round muffler. I am not sure why they make both styles. For fitment? Is one louder than the other? I don't think that one performs better than the other... this is according to them anyway.

Any experience or advice is appreciated!
Stephen

For reference you can go to the summit website above and plug in the following part numbers that were recomended from borla for a racing exhaust. Oval 40575 and round is 400373 (This round one is designed for rotaries)

[Greg Gauper]

I've been running a Borla XR-1 Oval for several years on my H-prod Honda.
Very happy with its performance. It is very quiet, yet makes very good power.
I usually hit around 89-90db for sound.

Fitment is a bit of an issue for me due to lack of ground clearence. I have to use my old IT tires on the rear to load the car on the trailer, but that has more to do with my trailer ramps than anything else.

I have a small turn down just behind the driver. As such, it is makes the car sound much louder inside than outside. I suspect if I had a traditional rear or side exit it would be much quieter inside.

[TStiles]

I have a small turn down just behind the driver.

Please be careful where you exit the exhaust ... I had a buddy that terminated his exhaust " just behind the driver " on a miata ... The hot exhaust heated his fuel tank , the gas cap pressure relief failed , pressure built and the filler hose exploded , filling the car with a massive vapor cloud @ 90 MPH

Me thinks he was very , very lucky :o

[Greg Gauper]

Yes I am aware of issues that others have had with exhausts exiting behind the driver.
I run a fuel cell, not a stock tank.
My turn down does not point towards my cell.
I do have a heat shield in front of the cell as a precaution.

[mossaidis]

To add to the intel here...

I run a tunnel dump exhaust, 2.5" ID to 22" long/4" OD Magnaflow resonator to 3" down turn "just behind the driver". I blow 99 db at LRP, 98 db at NHMS and after a 20 minute session you might as well fire off a piston near my head... I won't care (READ: numb).

I will be at the June 18th LRP event with that 99 db exhaust. I hope I can get a similar setup as Greg mentioned before the July 2nd event at LRP. Being that loud, I will never be able to run my car at HPDE's other than at WGI, I will piss off every track neighbor and the annoyance of racing will grow for me.