Yep, that looks like a good design. Good luck in your quest for silence.

 

Thats exactly what I had pictured in my head Doc.

 

Maybe it's the artist in me, but does that look a little weird--the resonator thingy between the two other thingies?
Especially with my unfortunate shading...

 

lol, yes it does. It would be extremely hard, since you have no piping after the mufflers, and im not an sound engineer. but its also possible to reduce the sound of the exhaust over all ( not sure if it would work for resonance,but i believe it would) if you got a sound calibration of each muffler, and then had "tuned" pipes of DIFFERENT lengths coming out of the back of each muffler in an attempt to have the peaks and troughs of the sound coming out of the two mufflers line up opposite each other in your 3000-4000 range, at least reducing the sound output
Bose does a similar thing with their sub woofers, except in reverse and have the ports on the inside tuned so the negative waves from the back of the woofer are delayed just enough through the tubing on the inside, that when they come out of the port they help to clean up some of the noise of the front output, and also line up with the front waves magnifying the sound output.
It would be hard to get right, but you could try contacting a sound engineer and get their opinion.

 

I got an email back from the dual bypass muffler people, who seem to have a lot of experience with Hondas and other 4 cylinder motors. He said the following:
1. The Helmholtz resonator won't work, but will cause more droning.
2. Chambered mufflers like the Sweet Thunder are not designed for 4 cylinder motors
3. I need lots of big packed flow-through mufflers in the system.

Aaargghh...

 

I tried two cheapie "glass packs" on my S, exited out the right rear side, ala
Cooper. No drone but it sounded like a giant hair dryer. Stock one went back on.
Maybe with some good quality "packs" and a straight through application it may
sound good(?). I do know these would be less expensive to experiment with.

 

exactly why I built these

nothing like them in the world

 

Sport Compact Car had a really interesting article a few years back about flow-through mufflers. It had to do with the turbo Focus project car they were building.

Essentially they found that they could use the fluted cheap cherry bomb mufflers without HP loss provided that the smallest internal diameter (including the flues) was the same as or larger than the rest of the exhaust system.

Focus Sport used this discovery to manufacturer a "stealth exhaust" for the ZX4 that is way quieter & pulls exactly the same as the non stealth system.

Also over the years SCC has had quite a few exhaust systems ceramic coated & says that it makes a huge difference in noise if you have the expendable cash.

 

MASSIVE DIFFERENCE BETWEEN A TURBO AND SUPERCHARGED CAR!!!!

If you heard Longboards car with the Rotrex vs the M45 you wouldn't believe it.... the EATON is a NOISE MONSTER through the exhaust.

It's so much quieter and the turbo is even more quiet

it takes a totally different exhaust to quiet the car.... this is why I had to build those special mufflers to quiet the car
there isn't anything on the shelf that will do it when you get to the big power cars

 

Doc Phil,

What diameter pipe are you using for your set up. And are the dimensions the same for the entire system from header to tailpipe ?

 

Ah, the wisdom of Jan! ...and those cool mufflers to back up everything he's said. Unfortunately there's a $415 RMW cam calling my name, which is the same price as the dual bypass muffler from hytech, or the cost of messing around with more mufflers and packs and assorted thingies.
I think I know my course...I hear the cam calling...

Eurothrasher. 2.5" the whole way.

I'm out.

 

Your system set up seems to be a real "free" breather - some engines actually require a certain amount of back pressure and with that comes the tuning you desire.

Have you thought about using a Supertrapp muffler set up ? It worked great on straight pipe set up's on some V8's I've done for track and awesome on a Harley.

http://www.supertrapp.com/product_se...rsal/index.asp

 

The standard Borla for the MCS has a nice mellow sound with only the slightest of drone in a very short range. After ceramic coating the entire cat back, sound levels reduced further and done was almost eliminated. But, after hard driving the sound acquired an unpleasant woody quality; very annoying from outside of the vehicle. In conjunction with a free flowing header, more annoying, even inside the vehicle. Not excessively loud, more like boards slapping together. I now know it could have been softened with a fat resonator. My recommendation for ceramic coating on a cat back is to confine it to the tips.

 

God I wish you would sell me one of these already...

 

you can get one but you may need to re-finance the house

 

Don't you mean "re" re-finance

 

space for these type cans ?

http://www.millteksport.com/product....fm?articleid=4

or is the battery box pinching too much space?

also the jcw cans seem to hang low, are they a good soloution sound wise [if not for power]

 

I doubt any aftermarket exhaust from another car will fit in the MINI but you could be the first to try

 

You could try as Jan suggests, but I'll bet there's not enough room for that system and a battery box. The JCW cans are the same size and design as the Milltek ones for the MCS. Actually you'd think you were seeing double if you laid a Milltek and JCW catback next to each other...

 

At least for my 2006 GP, the Milltek and JCW cans are different. The Milltek cans are much smaller. I switched from a JCW cat-back to Milltek. You can see the JCW cans from the rear of the vehicle but not the Milltek cans.

 

Well being the *** that recommended the sweet-thunder to the good Doc I feel a little bad. I guess the Rotrex really changes the sound. I run the RMW race header to a sweet-thunder down the center to the new style magnaflow rear section which just sounds awesome.

Longboard

 

Keep rubbin' it in, will ya?

 

Longboard--your suggestion was great, and given in the classic NAM tradition. When I talked with the ST people I never even broached the subject of 4 cyl verses 8 cyl, supercharged verses NA, etc. I take full responsibility and I wish I could use the system as I really like the way they manufactured it, and the tips are truly unique. But in the end, I can't keep throwing money at this experiment when I simply MUST install an RMW cam. It's time to get serious and remove something from the engine (!!)

Someday I might get the HyTech dual bypass muffler...

 

By the way, Doc... your priorities are good - because I agree that you MUST install the cam.

You'll like it.

 

On behalf of all the lurkers like me, thanks to the good Dr. and all who responded, (except Paul the cammer bragger, yes I'm just jealous ;-0), for an interesting and informative read.

It's neat to have you guys pushing the envelope and looking for more elegant solutions to our common problems, and sharing the evolution with us.

BTW, I had a 5.0 Mustang with a B303 cam and dual Flowmasters and it droned so bad I sold the car and bought the MINI, so not all drones are bad!