Check out SuperTrapp’s Universal Slip-Ons for custom bikes or café racers
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I’ve been a fan of SuperTrapp exhausts after riding a friend’s Harley-Davidson Softail Night Train in the 1990s. The blacked-out beast looked lean and mean, but with its OEM pipes it sounded like a wheezing moped. The next week my buddy scored a 2-into1 SuperTrapp system that I helped install in his driveway in just a few hours. The new exhaust gave his Hog a very distinctive and pleasing exhaust sound and thanks to improved power, the riding experience was vastly improved.
This is when I decided that some day I too would rock a SuperTrapp system on my cruiser. That actually never happened because I ended up building an old-school 4-speed panhead rigid, and using this type of exhaust would have been pure heresy. I kept that SuperTrapp wish on the back burner anyway and recently found an unexpected way to make use of one of their products: my ’07 Ducati Sport 1000 Biposto. A naughties version of a seventies café racer, the Sport 1000 is no cruiser (although it uses an air-cooled twin,) but I thought that its vintage DNA called for a pair of cool megaphones. This is what led me back in the direction of SuperTrapp and its universal-fit mufflers.
Chromed universal muffler with stack of discs and standard closed-end cap (optional open end available).
But before we move on with this install and for those of you who may wonder how pipes with a solid plug at the end can possibly do their job, here’s the skinny on SuperTrapp’s unique Tuneable Disc Technology. Indeed SuperTrapp mufflers feature an end cap; instead of letting spent gasses come straight out the muffler’s body, they are diffused through a stack of stamped stainless steel discs. Tuneability is the name of the game here: the disc stack provides a scavenging effect because the gap between each disc ranges from .023 inches on the inside of the muffler, to .028 inches on the external open edge. As hot exhaust gases pass through the discs to exit the muffler, they enter a larger area that causes a pressure drop as the gas expands while creating a scavenging effect for the hot gas still inside the muffler.
This official SuperTrapp video tells all about assembling and tuning your disc stack.
Each muffler comes with 12 discs that allow you to adjust, or “fine tune,” your motorcycle’s sound level, powerband and performance. Adding discs increases the size of the exhaust outlet, increases exhaust flow and exhaust tone while reducing backpressure. More discs move the power band up to give you more top-end power, and lean out the fuel mixture. Removing discs decreases the size of the exhaust outlet, decreases exhaust tone, and exhaust flow while backpressure is increased. Fewer discs tend to increase low-end torque and richen the fuel mixture. For more technical information and to answer a wider array of questions, go the SuperTrapp Q&A page.
The ’07 Ducati Sport 1000 Biposto and its huge and heavy exhaust cans. They make great door stops now!
Back to our story: the Ducati’s original dual mufflers probably weighted 15 pounds each, they were huge, rather ugly and cost the 92-horsepower L-twin engine several ponies. So last year I considered upgrading the bike to run the factory-approved Termignoni replacement mufflers and computer chip… until I found out that it would set me back about $1,600. Now I understand the plush leather couch, the big screen TV and the endless supply of cappuccino in the customers lounge at the dealership. Scratch the Termis, there had to be a better way.
Painted hi-temp black, the Emgos Looked very sharp, but didn’t sound so good.
I went back to the drawing board, or in this case to the internet, where I searched for inexpensive slip-ons. I was on the market for vintage-looking reverse cone megaphones and sourced a pair of chromed Emgo mufflers. I was able to adapt them to the stock headpipes, using a merge collector bend (that’s a fancy word for an elbow but it will make you sound like a stud if you use it). In this case I calculated the ideal bend that would have the mufflers line up with the road by using a plumb line and construction paper laid out on the garage floor. I found that I needed a 20-degree bend and ordered the merge collector bend fromSPD Exhaust. I ordered 2 of the following part number: MCB20175-18. These Merge Collector Bend are made from Mild Steel with a 20-degree bend, 1.75-inch OD, 18-gauge wall thickness and retailed last year at $16.72 a pop + shipping.
If the super cheap Emgos looked good on the motorcycle, they made me loose torque and were exceedingly loud, especially for a bike that can rev up to 8,000 rpm. So I installed home made baffles and my own glass pack system to bring the exhaust note from unbearable to obnoxious, but eventually grew tired of the high-pitch sound and even went back to using the stock mufflers for a while. When selecting the stubby, small-diameter Emgos, I had forgotten a basic rule of exhaust tone: the bigger the muffler size, the deeper the tone. So this is how I finally saw the light and came full circle with my interest in SuperTrapp and their 4-inch universal slip-ons.
I ordered the brushed stainless steel slip-ons and used the optional competition-only open-end caps in combination with the supplied closed ends (now painted hi-temperature black). It looks racy but the muffler retains full function of the disc technology.
Emgo cans use a clever steel channel with a keyway so you can insert a captive nut and bolt the muffler in place. I used a Dremel with small grinding disc to free the channels from the old muffler bodies and weld them onto the SuperTrapp units.
Available in Straight Cut Satin or Polished Stainless Steel, the Universal Megaphone Series Slip-Ons have 19-inch cone body (17.5-inch cone + 1.5-inch inlet). They come with twelve, 4-inch discs (add discs to increase horsepower, exhaust tone and flow, subtract discs to reduce sound and increase low-end torque). Since these are designed to mount on any bike and even on cars, they include a simple bracket/tab that you need to have welded onto the body. I wanted a less conspicuous attachment and decided to make the install a bit cleaner by repurposing the mounting bracket from the old Emgo mufflers.
Dick Stones is an old-time hot rodder with true grit, a steady hand and a talent for TIG-welding metals that melt at different temperatures. He was the guy to get the job done and a bonus, I got to hang out with him amid his fleet of flahead-powered hot rods.
After experimenting with various numbers of disc, I ended up using 4 out of the 12 supplied discs. This number seems to give me torque where I need it most often and a very limited amount of backfiring when coming off the throttle.
Supertrapp’s quick guide to selecting the right muffler for your application
In this video, the engine has been started cold so you can see how exhaust gases exit around the entire perimeter of the disc stack. You will also get a good idea of the Ducati L-twin sound. With 4 discs, it really barks without being excessively loud. Try stacking more discs for a louder tone.
