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I english wheeled some alum and attached it to my roll cage to reduce the muffler noise. It works quite well as it takes the noise level from ear plugs to OK to talk to passenger. It looks better than the pictures show but any idea's for a better finished look ?

Starting on replacing my hood and kept staring at some acylic sheet that came off an exterior sign. Just had to try it out as a hood. After a father's day morning of work it was a fun failure. I heated and molded in the needed bulges in the top. The sheet shattered as you can see in the second photo, but for practice I molded the one side in it's curve. Sheet had 10 years exposure to sunlight but behind vinyl. It would be great for show but I doubt it would hold up to the turbo heat coming off. Ok back to the alum I have waiting.

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CMC frame the GRM original build, now turbo miata track/street 311hp, complete but always being updated. thanks to LocostUSA Forum

I definitely like your aluminium "wings". I have felt the hot air rolling up the rear of the cockpit opening and wondered if a shield there would help. I guess this is the answer. Did you find it easier to talk due to the exhaust sound or the wind buffeting reduced? Maybe both?

Nice try on the clear hood. That acrylic doesn't stand a chance with your turbo heat!

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Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

For my car it was the exhaust note. I am trying for a quite exhaust but power/weight has the priority. With the rotary perhaps adding some sound deading will help you. I have thought of it as making it a nice arm rest.... but then next step might be adding a cup holder...
Plan to add wings to the windshield as the wind buffeting is bad. I could just drill thru my polycarbonate windshield but will look for some hardware when its time.

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CMC frame the GRM original build, now turbo miata track/street 311hp, complete but always being updated. thanks to LocostUSA Forum

Try rotating the exhaust outlet down 30-45 degrees. That should help disburse the sound. No cup holder required.

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."
Ultima Spyder, Northstar 4.0, Porsche G50/52

You could try it. I've found it makes things noisier.
Cheers - Gavin.

I will try the rotation when I bolt up a Laguna Seca spec ( decibels checked) muffler, its welded in place with only 120 degree rotation available. I've got 2 - 3" Burnstainless inline now that I found on ebay used, they have held up much better than Dynaflow/ dynamax ? mufflers, the second set burnt out in two weeks. thanks for the imputs - Congrat's on getting the CMC rotary up running - The Ultima site is great.

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CMC frame the GRM original build, now turbo miata track/street 311hp, complete but always being updated. thanks to LocostUSA Forum

But they must be a lot louder than a glass-filled muffler that's 10x the volume. I suspect the glass gets melted because the mufflers aren't at the end of a 5-ft exhaust with catalytic converters in between.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

Yes louder but for their size amazingly quite and very light weight. Next time my son drops by I will have him record and post on Utube or something. As you said the glass filled must have melted out and I was left with a straight pipe, could get new ones again with warranty but what was the point.

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CMC frame the GRM original build, now turbo miata track/street 311hp, complete but always being updated. thanks to LocostUSA Forum

While my car's not done yet, the Dynomax muffler worked pretty well - on the dyno, but if your two mufflers get you by the 92-db limit at Laguna you'll convince me to switch. I'm all for using mufflers that don't have "stuffing" in them (my SuperTrapp melted, too) but am suspicious that such small mufflers can work. Hoping for the best though.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I bought them more from some luck. I was reading up on mufflers, came across the Burnstainless for racing and then looked at ebay as a "why not" and found someone selling them for less than a 1/3 of retail in the size I needed. Yes my goal is to go to Laguna later this year, I will take a known quiet muffler to bolt up and then try these out after some runs and see if they pass. Any easier way to do a decibel check ?

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CMC frame the GRM original build, now turbo miata track/street 311hp, complete but always being updated. thanks to LocostUSA Forum

Yo, Twnpipe-
You might check and see if the local (?) SCCA or NASA group has a meter and if they'll let you (or help you) use it. Cars are usually tested on track with the meter 50 feet from the pavement.

H-T-H

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JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

Radio Shack sells db meters for pretty cheap.

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mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

The trouble with sound readings is that they depend so much on reflections. A true back-to-back comparison would be most helpful, but if you accidently change where the exhaust points when changing the muffler, it becomes hard to know if the improvement was the change in muffer, the new exhaust direction, or both.

On top of this, since my engine is turbocharged, that'll hopefully help cut down on noise and also cool the exhaust some. Hopefully it'll keep the Dynomax muffler from frying but I won't know until it's run hard.

Keep us updated, as I think everyone would love to have a small, light, all-metal muffler that really works.

_________________
Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I believe sound is on the right side at Laguna Seca, so your left side exhaust should help some. Also on the reflections, if your plans will allow, now that there is no direct line from the exhaust tip to your ear it might be interesting to actually rotate the exhaust tip to point in a ~45 degree upward angle* away from the car to minimize reflections from the ground/walls and maximize dispertion. While it may not be any quieter for the driver, it might knock one or two dB off as measured track side. Even though you can't predetermine what your actual measured dB at Laguna Seca will be, even a cheapy sound meter would definitely allow you to at least do enough testing to figure out generally what helps and what hurts. I believe the sound meter should be set for dBA weighting, as that is what will generally be used to record your car at the track.


* Exercise common sense regarding the use of such potential 'rain collection' devices.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

couple pictures. On the sound shield I painted the zip tie area on the cage black and it looks neater. Working on bending hood, I had to hammer out more space for the VVT area on the Miata and need to smooth it out. I used a very British tie down on front of hood as the small rubber straps have always concerned me at the track at 100 mph. The front one is stainless metal spring with very crude but strong appearance, perhaps I should put one on the back to match. The front fenders were just a temporary measure to cover my street wheels, selling these 17" and going to 15" for the street also. I'll let everyone know on decibels when I get some readings. Taking off next couple weeks to Seattle for first time cruise and vist my sister in N. Vancouver and couldn't convince the wife to take the "yellow car"

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CMC frame the GRM original build, now turbo miata track/street 311hp, complete but always being updated. thanks to LocostUSA Forum