Diffuser Disc Muffler

[mk e]

I have made two sets of header collector mufflers and will attach a couple of pictures of the latest for my 412. I also did the same concept for my 97 Ford diesel 7.3 using 3 1/2" tubing from down pipe to tail pipe tip. Used a 5" x 48" tube over it ahead of rear axle. From front for 12" I used a 14" chop saw, then from 12" to 24" position I used a 3" body cutter and rest of the inside tube un touched except for 4 cuts just ahead of rear of muffler 5" shell. Exhaust noise is very mellow and not too loud.

On my 319 or 347 the collector used 1 7/8" header tubes with a 3" outlet cut the same as pictures. Decibel level before was 98 and with this collector/muffler 85 with both on A scale and ??? don't remember the other additional option.

Sons 412 is 83/85 decibel. 2 1/8" in and 3 1/2" outlet.

Very cool!

any idea what it does to hp?

[Warpspeed]

I tried something like this many years ago myself, and it was very effective at attenuating the objectionable higher frequencies in the sound.
My system used two inch and four inch pipes with a fibreglass wool layer packed loosley in the cavity between the two pipes.
I think it would make for a very effective solution on a larger vehicle that had sufficient ground clearance.

The resulting system on my own fairly small car ended up being rather heavy, much heavier than I would have liked, and four inch pipe significantly reduced ground clearance, a problem I could see no easy way around.
For me it was not ideal from the istallation aspect, but it certainly worked very well, and on a much more suitable vehicle definitely well worth looking into.

[amcenthusiast]

SuperTrap mufflers were originally marketed for motorcycles.

As implied by name, they can 'trap sound' but also trap sparks.

Spark arrestor and muffler has broad appeal for off road motorcyclists.

Automotive marketplace is simply another way to sell the product.

I would not advise using off road spark arrestor motorcycle mufflers on a car.

On a mid-engined Lotus, you have a length limitation.

In order to make the car quiet (assuming no cat converters) you will need to fit the largest mufflers possible for maximum sound wave dissipation: the further the sound waves travel, the weaker they become. -Expansion also; when the exhaust pulses expand there is a cooling effect, the pulses lose heat, and with heat loss there is loss of energy, and with energy loss, there is sound reduction.

Do some research on 'Porsche muffler'; notice how the exhaust pipe dumps into a large bulb type chamber. And they simply appear to have a perforated screen inside -which kills sound wave propagation.

Otherwise, try to fit the largest two tube/turbo type muffler you can within the space limitations of the car.

-The overall size dimensions of the muffler is basically your 'gauge' on how quiet the muffler will be on the car, where 'smaller' is 'louder' and 'larger' is 'quieter'.

The overall size of a SuperTrap muffler is indicative of how much sound absorbtion there is ...without the restrictive spark arrestor plates installed.

We can't change the Laws of Physics. Study and learn more about sound on various websites like Georgia State University's "Hyperphysics' website.

[chimpvalet]

I'd say Amcenthusiast sums up pretty well what is the consensus on this topic, thanks to all for many worthwhile thoughts.

As a Lotus owner/enthusiast I tilted in the direction of S/T as much because of their remarkably compact size as anything. Years ago, running Laguna Seca on a Club trackday, I was meatballed for excessive dB's while running my own, custom take on a small, 40 Series Flowmaster. Damn thing was loud but had been shown to attenuate when A-B'd with straight pipe. Luckily for me the good folks at Jim Russell Driving School were so kind as to not only lend me an S/T disc/cap unit but also rig it temporarily onto my tailpipe, at no charge!! That kindness saved the day for me and I have enjoyed the memories ever since.

The Cyclone Sonic Turbo style mufflers were tried on a buddy's Esprit where we found the baffle plates were knocked loose in short order. I had a reverse flow type made up for my Elan which was heavy and fully welded so durable, just a bit hard on the fiberglass where it was hung. Eventually I resorted to an S/T 5" disc/cap package for weight and aesthetics ( car weight 1550 lb., less driver ) and grew to like the growl in-car. Ran well on track at Sonoma and, interestingly, sound levels were unremarkable from spectator points of view. I imagine the diffuser aspect of the design may account for the difference between apparent sound levels up-close and at a distance.