LocostUSA.com

The bottom line is that the bigger the muffler the quieter it is.

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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 placed the sound meter approximately 3 feet behind the vehicle as shown. Testing was outside with vehicles all around, so I expect that reflected more noise into the meter. The engine block is also exposed to the meter. I think most testing is done at about 12 feet away but I didn’t want to move everything for that. I feel I accomplished enough in testing, removing, building a new system, painting, installing, and retesting in one day.

The existing muffler was a Walker Thrush 17702 universal, connected to the original system which was thick walled tubing. At idle it was 80.5 db. I revved it up a bit under the max hold setting and got a peak of 96.6 db.

The new system is a Walker Quiet Flow 22483 made as an oem replacement for early to mid- 90s Toyota 4wd pickups with the 3.0L v6. The system was assembled from two 180 degree 2 inch mandrel bends. At idle it was 71.9 db, a reduction of 8.6 db, but the tone was deeper and there was a rattle I have not investigated yet. It also seemed less noisy inside. I think I revved it up higher than the previous test since it was quieter and I do not have a tach, but the db was still lower at 96.3 for a reduction of 0.3 db plus the new rattle.

Aesthetically, it was not made to be seen. Mine had a couple dents from transport and I could see some of the internal baffling had made light creases in the outside, so a smooth cover would be a good idea.

I included a drawing on how to add a tail pipe like the caterham 620, which also have a small resonator sideways across the back of the car. There will be a loss of ground clearance so the car should have at least 5.5 inches leaving 3 inches for speed bumps. I think a tail pipe would make as big a difference as any muffler would alone. I’ve seen donks run the tail pipe around the inside of the rear fender so the car can be lower.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

At driving events I've been to that monitor sound, they take readings at 50 feet. You may well be fine with those last mufflers.

_________________
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/

The more pipe after the muffler the quieter and smoother sounding the motor will be.

_________________
mobilito ergo sum
I drive therefore I am

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

An 8.6dB reduction at idle is amazing improvement. Well done.

_________________
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

Thanks Chuck. For those that don’t know, a loss of 6 db equals half the sound pressure. I was “baffled” at how loud this rx7 is with home made mufflers:
https://www.youtube.com/watch?v=iRtc1Y4m798

Interesting comparison of these bikes exhaust systems to a Honda:
https://www.youtube.com/watch?v=cCu6niZr_sc

Totally agree Carguy.

I’ll test again at a distance of 50 feet and 12 feet, add a washer to the outlet, and use some self-adhesive flashing (like Rob used on his trike) to some of the panels that are resonating. I also need to add a hanger on the right side to hold the system up. I may loop the system for a right side outlet to see the effect of a longer tail pipe.

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

This isn't meant to be a solution to the specific problem posed in this thread, just an idea for further discussion. It's a very simple tool for forming baffles, motorcycle style. It's about halfway down this page:

Baffle making tool ==> http://www.jockeyjournal.com/forum/show ... post240160

I have it in mind to design/make my own exhaust system eventually. My idea is a little different: 6 individual tubes of my V6 run to the back of the car. If you look at typical Euro or Asian motorcycles, they seem to do a good job with pretty simple mufflers and I'm wondering if you can't use that technology and apply it to each cylinder of a V6. Obviously, there are packaging issues, but with baffle-style technology, I think they can be overcome.

What do you think about the possibility of their noise-reduction capabilities? There is a specific DB requirement for California, my state of registration, and that was 95 DB using the SAE J1169 test, last I checked.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Lonnie, I built baffles like you linked to in your post and they were still really loud. I bought some glasspacks (Thrush I think) and welded them in my side pipes and it's way quieter now. And the glasspacks are not exactly quiet either.
Kristian

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V6 in a book frame build. Now registered.
viewtopic.php?f=35&t=7587
viewtopic.php?f=33&t=18172

For what it is worth I had some chain link fence post caps and drilled a series of 3/8 holes in the caps and slipped them on my tailpipes.
The didn't seem to change the noise level in regards to my hearing.

Al

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Super Seven 3.4

@turbo_bird, raceral;

Shoot, that's discouraging. Motorcycles have smaller cylinders (smaller bang), but the simple muffler systems they have seem to do a pretty good job. My reserve option is to hide the mufflers in a bustle structure similar in concept (but not the same size or design) to the rear of a Donkervoort, like the photo below. So, the mufflers would run side to side to side, with the drivers side exhaust entering there and exiting on the passenger side. Passenger side to do the opposite, of course.


That would be a lot more work, but there would be some room for cambering instead of just baffles in that case.

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Speaking of solid engineering, check out the cans on this.

I know you asked the other guys Lonnie, but for a v6, I'd consider using the 1987 Buick Grand National muffler, Walker 22395 ($52) with a single pipe down each side to the transverse dual inlet and dual outlets under the rear kick up. If it is too loud, add a muffler on each side also. Should be very clean. 2.25 in and out.

http://www.summitracing.com/parts/wlk-2 ... plications

_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Thanks for the suggestion. It looks like a good solution if you have the room. I'm hoping to avoid two things: 1) having the mufflers along side the car; and 2) having the exhaust exit near the driver and passenger where they will be pretty annoying, I think. A third goal is just to have the cylinders all exiting via their own pipe. I just like the way that sounds.

Than said, my first go-around will be utterly typical. I'll use the stock headers (actually a pretty nice pair of shorties) out to side pipes and some elementry kind of muffler like a glass pack with exits near the rear fenders. That will just be to get it registered. After that, my evil exhaust program gets the go-ahead.

I don't know what the AMG setup is about, but it's interesting. Could they be a pair of exhaust-powered clothes dryers? Man, those mufflers are huge!

Cheers,

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Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886

Few years ago I read a paper about mufflers, and what the optimum sizing was. This paper suggested that for your standard road-car muffler, the ideal size was.... massive. I forget the exact dimensions, but garbage can sized sort of thing. I guess AMG read that paper

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Build log: viewtopic.php?t=9291

Do individual pipes sound different than putting them all together? With a V8 when you group them into each side it sounds different because the firing is not even, but if you put them all together I think it becomes even and wold basically sound the same as 8 individual pipes, except you're likely to face 4 of them more directly.

Since the sound of each cylinder happens at a different time, using one muffler makes sense. The pulses on a V6 just don't overlap much. Putting a little more effort into building one muffler shared by 6 gets you way ahead of anything you can do building 6 different units...

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Marcus Barrow - Car9 an open design community supported sports car for home builders!
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I can certainly appreciate a nice set of cans.
Kristian

_________________
V6 in a book frame build. Now registered.
viewtopic.php?f=35&t=7587
viewtopic.php?f=33&t=18172