My failed muffler design

[Billzilla]

I thought I'd come up with a great idea of how to make a quiet muffler with no restriction, but to cut a long story short, it doesn't work.
Sound is made up the air particles wobbling back & forth. The more they wobble, the more sound. A simplistic expanation, but it'll do for now.
If you can chop up or make the pulses smaller, then there's less perceived noise.
So the muffler I though up was supposed to do all that, but with no baffles or any real restriction. I've had the idea for a while, and finally got around to making it. Pete (Rz from Performance Forums) did all the welding for me 'cause I suck at fabricating.



That's the three main parts to it you can see - the two pipes, one in one out, and the central chamber. You can see the chamber below ...



The pipes have a lot of large holes in them, and they bleed off the pulses bit by bit into the chamber. Then the opposite happens when the gas goes out the exit. The pulses all bounce around in the chanber and mix up with each other, so it should have shut the thing up a bit.

Here's how it looks on the back of the Sprinter. (convenient noisy test car)



Okay, when dirivng it, it pretty much did the opposite of what I wanted it to do - It was raspy, loud, and sounded crappy. Pete & I have since shut it up a lot but by adding some perforated tubing inside, and that's why it's a failure - It was supposed to work without all that stuff.
Now, it is still raspy at times, but is also pretty quiet at some revs and throttle settings. There's still some more fiddling to be done, but the main concept is a failure.
Just thought some would get a laff or interest from it.
(And look at Pete's cool welding skills)

[jezza323]

awesome welding, interesting idea...shame it didnt work out

better luck with the next one bill

[infotechplus]

Just thought some would get a laff or interest from it.
(And look at Pete's cool welding skills)

Love to but can't see a thing Bill. What's the go?

PS. Interesting theory - shame about the proof-of-concept

Cheers,

Peter

[Screamn_Sleeka]

Seems that anything that even slightly resembles a turbo is bad for the exhaust.

Im sure you could sell them to kids, call it the "Rasponator" or something, increases 20% hp.

[twentyEight]

Photo's are working here...

It's quite a good theory Bill, and I think you've got a great idea for a performance part that, if you can get it to work properly, will market quite well...

Keep working on it, but be very careful posting Ideas like this up online, as people will steal your idea and beat you to the final release... Although, you now have proof of a date of concept...

[thechuckster]

maybe take a leaf out of the design book for recording studios:
-no parallel surfaces
-pliable coatings that don't vibrate in sympathy

no idea how you can replicate that with metal and hot air, but when you walk into a well-designed studio, it's amazing how a big room can have no echo at all.

[oldcorollas]

perhaps the holes are too big or the air is running around the outside of the pipe?
being a fluid, when turned like that, it will stick to the outside... although sound is made up of pressure pulses mixing the pulses is not so easy to set up destructive interference at a wide range of frequencies...

perhaps if you replaced the holes with slits, ala the old audi(?) turbo intake manifold, with the total slit area the same as the pipe cross-section (ie, pretty thin slit).
no restriction is hard cos any change in direction gives rise to restriction.. but...
anyway, awesome welding

Seems that anything that even slightly resembles a turbo is bad for the exhaust.

?? turbos make exhaust much quieter/smoother by chopping exhuast into little bits..

[Ben Wilson]

Are the holes evenly spaced/sized? Could you be setting up a bunch of harmonics in the central chamber?

[Wildsupra]

I love it when people try out their own theory's regardless of what other people may think.

The design in itself appears to be good, however i think the holes in the centre of the chamber are far too big. Something to consider would be the inlet and outlet diameter's of the pipes in relation to the size and amount of holes in the centre chamber.
If you want as little restriction as possible and the smoothest flow, would you not be better off keeping the inside holes of the muffler the same over all surface area of the inlet and outlets. By means of a lot of smaller holes. For example maybe 40 10mm holes.
I'm not thinkin straight enough at the moment to actually work it out, but basically drill a certain number of small holes on the inside which equals the same hole area of that of the inlet. Then to help even further add a centre baffle between the 2 tubes with also the same amount of holes (hole area)

So in the end you will have 3 sets of say 40 holes is each "baffling stage" however without any glass packing and keeping the hole areas the same it shouldnt restrict flow.

We make mufflers at work for vintage and veteran rolls royces, admittadly they are quite a bit bigger than yours, but we use a similar principal to what i tried to explain, but we normally redirect the exhaust flow through about 6 or so chambers. The end result is a 7.5litre straight 6 engine that is near on silent at the rear end.

Hope that helps
Matty

[infotechplus]

Ahhhh, I'm at home and can see the marvel of engineering that is your design. Very ingenious indeed. I can just see you now on The New Inventors.

Are you going to keep playing with the design? Don't give up on it just yet.

BTW, how heavy is the unit itself compared to a standard type muffler?

Cheers,

Peter

[mic*]

It would be difficult to model whats gonna happen accoustically thru the rev range. Makes R&D a pain...

If it were my idea and i was gonna try more options, foremost Id suggest that the outlet is not parallel to the inlet - ie you need to clock your muffler Secondly id suggest that the holes inside each scroll are sized differently on the in scroll compared to the out scroll. Also, id try to use something else in place of the bolt as your centre pin - ie something not round...

[oldcorollas]

bah, just stick a T04 turbo on there, with the compresor outlet and turbine inlet connected

i wonder how a stationary impeller would go at breaking things up?

heres an idea (attached) make some small U shaped tubes and connect up the holes... the "last" hole of the first tube to the "first" hole of the second tube.... since oyu are experimenting
not much effort except getting tube in that size and radius (copper to play? even PVC for a short time?)

[Draven]

Biggest problem will be that type of muffler will (as you found out) generally be really good for certain rev bands, and really crap for others due to change in frequency. Even professional audio areas get tuned for a "preferred" frequency of sound (opera house, etc. Anyone who says Ent Cent will be shot).

I love the idea tho

[Billzilla]

Are you going to keep playing with the design? Don't give up on it just yet.

BTW, how heavy is the unit itself compared to a standard type muffler?

Yeah I'll keep fiddling, but the concept of making it muffler without baffles and having it easy to make (ah-hem ...) didn't work, so on that criteria it's a failure.

It's about the same weight as a regular muffler.


Stewie - Yeah mate, stuff like that I really should try as well I guess.

[JustenGT8]

If you are willing to have a crack at a totally different design Bill, a gun silencer is the model i have been keen to scale up to a full sized muffler. Should have nothing to impede flow as just a series of lots od small expansion chambers. The killer is weight as all the baffle plates would soon add up, even if made from light guage. I was thinking that alloy plate would probably handle the heat as doesn't melt until over 800 deg and exhaust gases should have cooled well below that by the rear muffler?

I have seen a similar design work OK on stationary diesels but wasn't pretty and some effort would have a much nicer design.

What do you think?

PS dibs on royalties when the millions start rolling in