Diffuser Disc Muffler

[chimpvalet]

Looking at specs for street exhaust for my Lotus Esprit, on the way to having a complete system built. The Supertrapp muffler, discs only, has appeal from the packaging point of view in this mid-engine situation. Anyone care to share knowledge of how these mufflers deliver from a power or noise perspective?
Steve

[Kevin Johnson]

I have two of them on my old Benelli Sei so 3:2. They were fabricated back in the 1980s and I swapped them out for the 6:6 pipes. Noise level fine. Induction roar from the 6:6 Honda 500 carbs is significantly louder. No dyno data.

When I last did a search on Supertrapp systems I recall that they were not the optimum setup for an exhaust.

[Walter R. Malik]

I have witnessed the "Supertraps" used where there are short slightly turned tailpipes, (the same diameter as the inlet), which were added to the rear of the muffler and not using the discs as discharge but, as a "silencer" being near the end of the exhaust stream.

In both those instances, the owners were greatly satisfied with the minimal loss of power, although I have no first hand information.

[twl]

On our single cylinder 4-stroke vintage motorcycle applications, we found them not very good.

[Warpspeed]

It seems the supertraps work best when placed right at the very end of an exhaust system, and the more pipe volume you have between the engine and supertrap, the better they work.
On a normal front engine, rear exhaust, "car" type application they work great, but for someting like a motorcycle with short pipes, not nearly so well.
Mid engine, probably somewhere in the middle.

[chimpvalet]

Curious for more on Walter's example. If I understand the scenario, the disc pack is attached to a supplementary tailpipe but does not act as discharge? Do you mean, perhaps by your reference to a "silencer" that this is a case of flow passing through a disc stack with no end cap? In other words, the disc stack is "spliced" in between muffler and original tailpipe?
Steve

[oldjohnno]

Their claim to fame is "tuneability" - ie. by changing the number of disks you can choose between too loud or too restricted or some combination thereof. I don't know of anyone who has run these with complete success, and as others have commented if you must run them get as much volume as possible upstream to help crop the pressure peaks.

[ZIGGY]

"Rattletraps"...if that kind of noise bothers you.

[mk e]

On our single cylinder 4-stroke vintage motorcycle applications, we found them not very good.

Same result on H-D engines. It seemed that if there are enough discs to not cost hp they really don't muffle at all, and when the noise is tolerable the hp loss isn't....10% ish loss IIRC. I found it much better to just have 2 mufflers depending on the noise limits I was dealing with than to mess with the supertraps.

I'm going to try an ECU controlled by-pass valve on my current build (car) so there is no changing anything other than maybe a switch on the dash.

[MadBill]

As above negatives. Either too loud, too restrictive or both. Per Carroll Smith of GT40 at LeMans and the "...to Win" books fame, notorious for rattling the rings out of the old Formula Atlantic engines. Supercrapp.

[Walter R. Malik]

Curious for more on Walter's example. If I understand the scenario, the disc pack is attached to a supplementary tailpipe but does not act as discharge? Do you mean, perhaps by your reference to a "silencer" that this is a case of flow passing through a disc stack with no end cap? In other words, the disc stack is "spliced" in between muffler and original tailpipe?
Steve

All the disks are in place however, the end-cap has a hole the size of the Supertrap inlet and there is simply a short bent piece of tailpipe, (about a foot long, big radius 45 degree), welded to that end-cap; at the end of the exhaust system. These were all the long Supertrap mufflers having the megaphone muffler with the disc pack on the end; not just the disk pack...

All I can surmise is that it must act similar to a pistol silencer.

[Billzilla]

A bit of a thread drift but it might be of interest to some.
It's a long story but I came up with an idea for a muffler that is supposed to be very free-flowing but by the way it's shaped chop up the pulses in the exhaust gas so a to try to make the tone lower and less sharp.
As you can see it in these photos, it doesn't work as well as I'd like.





The car it's on has a Toyota 3SGE two litre and it's fairly quite at idle but still has a bit of a bark with some revs & throttle on, but (subjectively) doesn't get a lot louder when more revs and throttle on. So a partial success ...?
The bottom of it has a nut so I can take the cap off to change the internals - it currently has none - but I plan to add a perforated tube to the middle, along the axis of the threaded road, and it'll have muffling material in it to help soak up the pulses.
The car isn't registered right now so I can't drive it to test that ...... one day I will though.

[pcnsd]

On our single cylinder 4-stroke vintage motorcycle applications, we found them not very good.

Same result on H-D engines. It seemed that if there are enough discs to not cost hp they really don't muffle at all, and when the noise is tolerable the hp loss isn't....10% ish loss IIRC. I found it much better to just have 2 mufflers depending on the noise limits I was dealing with than to mess with the supertraps.

I'm going to try an ECU controlled by-pass valve on my current build (car) so there is no changing anything other than maybe a switch on the dash.

X3. My experience on single cylinder M/C using either tuned primary to megaphone/muffler or tuned total length to muffler systems is a closed end cap creates a powerful reversion pulse and an RPM no pass zone. You can pull your air filter and watch the fuel charge get blown out the carb intake at the affected RPM. Possibly not an issue with autos. Tunable? Not by my definition. Adjustable sound level...maybe.

[BirdMan]

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.

Uncoated headers 007.jpg

Uncoated headers 008.jpg

[pamotorman]

I used a muffler on my dirt bike that had a high temp rubber flap on the end that at idle and low RPMs stayed mostly closed but at WOT the flap blew open for a straight thru exhaust.