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Ringa,

after a lifetime spent modifying bikes I learnt long ago that exhaust design is a mix of art and science. The science is all to do with pressure waves, back pressure and flow rate. The art is getting it to look right and to sound right... It is possible to have an exhaust that sounds wonderful but is quieter, on a db meter, than one that sounds harsh and aggressive.... It is also possible to make an exhaust that sounds fantastic but makes the engine run badly and develop less power than the stock exhaust.

At least the S&S twin functions, from an exhaust perspective, as two singles, no crossover or balance pipe. But I hope MMC spent more time designing and testing the exhausts than they did the transmission... Has anyone taken a M3W to a bike exhaust specialist like Zortstec or Armour?

"after a lifetime spent modifying bikes I learnt long ago that exhaust design is a mix of art and science. The science is all to do with pressure waves, back pressure and flow rate. The art is getting it to look right and to sound right... It is possible to have an exhaust that sounds wonderful but is quieter, on a db meter, than one that sounds harsh and aggressive.... It is also possible to make an exhaust that sounds fantastic but makes the engine run badly and develop less power than the stock exhaust. "
=!:)))

I think I have finally grown out of super noisy exhausts but it took 4 TVRs, Lotus Exige S Stage 3, M3W sports etc. I do love a burble on the overrun or the paddles on my M3 which has a modified exhaust on change down.

The standard M3W does sound rather good.

Which is exactly my point - all the circuit Noise Testers have their own process and therefore we cannot take one reading to have any relevance to another circuits' requirements. I carry a pair of slip-on 8" cans when I attend a track day now, just in case.

As others have said, decibel readings are a bit of a nonsense and it is the wave length that makes the difference.

I remember that, when waiting to race a TVR Tuscan at Donington, I watched the Civic CRX race. The Tuscans made a splendidly deep growling sound and you did not need ear protection at the side of the track, whereas a full field of CRX racers passing was phyically painful. The TVR barely scraped through the sound test, whereas the CRX was given the signature without any problem.

Anyone tuning a Harley for peak power will most always use a 2 into 1 type exhaust system.

On my last '08 110" bike, I had true duals and they told me it would rob power, which I was almost sure I could feel.

Sometimes something that sounds so very cool, is NOT he best for you.

I remember many years ago friends of my dad had Harley Sportsters and it was Halloween. They pulled their standard short pipes off and made up very long pipes that went low to the rear wheel and then swept upward about 3' each. These pipes basically robbed them all their performance.

I couldn't help but wonder the first time I saw a M3W how they ran as good as they did with that very long exhaust system. But if the cam is "adjusted" to run with the length of pipe and backpressure, I could see them working okay.

I know a tuner that does baffles for Harleys and also does his own dyno work. He's found that with his tune the larger baffles make higher peak power, but a mild loss in mid range. The smaller baffles, read quieter, made more average hp and lots more mid to low range torque.

I believe what most of you guys want is lower mid range torque and max peak at WOT.

I'm in agreement with Dan.
A cool 2 into 1 system on the passenger side or even, perish the thought, underneath, might work better than the "styled" side pipes.

Or perhaps a balance pipe connecting the two under the chassis like the Triking?

And Shmee, I follow both you and MMC on FB, my feed has been a blanket of blue this last week.

A balance pipe will 'balance' the exhaust pulses, which will take away the 'bark'. I prefer the 'raffish ripsaw' of separate pipes ...

Scmee out in London in the M3W