Back in about 1971, Triumph stopped putting its traditional tidy sausage-shaped mufflers on 750 Bonnevilles, replacing them with swoopy, Honda CB750-style megaphone mufflers. Very Buck Rogers. But young men, cash in hand, would ask at the dealership if they could still get, you know, the other kind. And we at the dealers had to say no. They were disappointed. Disappointed because for so many people, mufflers speak a powerful subconscious language. Don’t mess with it. Sausage mufflers belonged on Bonnevilles. They looked right.
Megaphone-mufflers remained fashionable only until “four-into-ones” took over—the unique style of the 1025cc “sit-up-and-beg” Superbikes of the late 1970s. Soon, everyone knew that four-into-ones made way better power than phony megs. It stood to reason, right? Race bikes had ’em. They hadda be good. And as soon as social pressures required mufflers on racebikes (1976-onward, pretty much), a big upswept can with a fiberglass-backed perforated-metal liner became the hot muffler of choice. Looking into those straight-throughs, you could almost see the exhaust valves. Naturally, this wasn’t quiet enough for production, so vaguely racy-looking upswept cans were filled with the usual array of really effective quarter-wave tubes.
That pretty much left us where we’ve been for a couple of decades now, with some small exceptions. A straight four-into-one gave way to the powerband-widening four-into-two-into-one pipe, but if you didn’t look carefully under the engine, a 4-2-1 looked just like its simpler predecessor. And, maybe because humans have bilateral symmetry (you know—two arms, two legs…), there were always a few companies that split the collector and put a dashing, upswept, racer-style muffler on each side.
The central issue of muffling is what I will call “the Sportster problem.” The Harley Sportster hit the market in 1957—in the sausage muffler era. Trouble is, there’s not room enough for a full EPA-approved array of free-flowing and quiet quarter-wave tubes in such little mufflers, so you either get stylish-and-restrictive or good performance with giant mufflers the size of RFD (rural) mailboxes. That’s why, so often, big-engined sportbikes have not one muffler (for years the racers’ choice) but two. That much volume is required to combine good sound control and free flow.
Enter Erik Buell, a man with his eyes always focused on performance. He sees all that room under the engine and comes up with his “torpedo-plane” muffler—a big, torpedo-like cylinder slung under the engine, with a little outlet out one side at the back. Yeah, it looks funny—call it “a Corvair muffler” if you like, but performance is good.
The stylists at the Big Four saw possibilities. What if the whole muffler could be concealed in the belly-pan? That would allow new visual solutions for the rear half of bikes, undisturbed by hot plumbing. Novelty! Increased sales!
Better yet, the wonks from the Mass Properties Department had a look. Bikes turn more quickly and require less suspension interference from damping when their major masses are pulled in toward the center. It’s the old difference in maneuverability between a 24-pound cannonball and a 24-pound ladder—the ball can be rotated in all directions a lot more easily than the ladder.
An alternative style put mufflers under the seat—a good visual solution but about as far in the “ladder direction” as you can go. Big cans on either side of the rear wheel were also “ladder-ish”—pretty far from the bike’s center—its engine. So you can bet that prototypes with Buell-like under-engine mufflers went into mass properties testing everywhere.
Production Departments loved the under-engine muffler because it’s hidden. That meant they could make a purely functional part that doesn’t have to be expensively “dressed-up” in eye-catching stainless or carbon fiber, as upswept mufflers do. Money saved! But the aftermarket resents being denied the usual place to present its logo or printed message.
With a car, you can close the lid (hood) on the perpetual war between available vehicle volume and the territorial claims of all its parts—the engine bay is packed full to the top. But on a bike you can still see the battle raging—many mufflers have been stuffed under engines but still squeeze out here and there, but we now have the problem of exhaust heat raising oil sump temperature.
There is a lot happening in research and development departments as manufacturers explore all the new possibilities and solutions. But any time there is an attempt to make a lot of power and pass EPA sound tests, the exhaust volume will need to be large. As this larger volume has become more necessary, styling continues to find ways to incorporate it into the overall design. As with many things, sometimes it works, and sometimes it doesn’t!