Superbike racing –––– such as Suzuka 8 Hours, JSB1000, WorldSBK and AMA superbike –––– is the top competition series between production-based motorcycles and runs under strict noise regulations. Japan Superbike 1000 for example limits the exhaust noise level to 105dB at 5500rpm which is relatively quiet for a race bike (especially when compared with MotoGP’s 130dB at 5500rpm for a four-cylinder bike).

“The Racing Department told us that the R-11 can no longer cope with the bike’s higher performance,” says Yusuke Yoneyama of the Muffler Development Department. “So we needed to design a silencer that would further suppress noise.”

The requirements were high. Engine performance, lean angles, weight, size, rigidity and other numerous aspects had to be taken into account in the design process. Yoshimura engineers finally came up with a unique and innovative solution –––– a square silencer.

For 2015, Yoshimura Suzuki Racing Team replaced the R-11 muffler with the newborn R-11Sq, but as they expected, “no one including rival teams and press noticed the difference except for Suzuki satellite teams.” The resemblance was deliberate as they share the same design concept.

The task was to increase the muffler capacity in order to handle the exhaust noise while retaining the core design, but simply enlarging the size of the R-11 will ruin the overall visual appearance. What they pursued was a subtle but distinct difference.

The R-11Sq has a canister capacity larger than that of the R-11 and is filled with more packing (sound-absorbing material). “It provides 2 to 3dB more noise reduction. Which might seem like no big deal, but it’s a huge difference.”

Structural rigidity of the muffler itself in turn becomes an issue since you are trying to turn a triangle into a square. “It took a lot of tweaking to optimize all the curvatures, corner radiuses, bending coordinates, welding points and so on from scratch,” he recalls.

Following the success in competitions, the R-11Sq went through the transition from the racetrack to the street. The R-11 on the other hand also has great style and performance, and it perfectly emphasizes the excitement and agility of supersports bikes, but some say it looks a little too small for 1300-1400cc mega-sports bikes.

“We were somewhat concerned that the R-11 might be a bit understated on bigger bikes. Then we realized that the larger, square silencer looks great on them.”

Not too big, not too small. Having the larger capacity makes the exhaust sound more sonorous and sweeter. It has a good silencing effect and it suits perfectly on big bikes. If you appreciate the modest attitude and sportiness in its appearance, this would be a great upgrade.

“The overall size is bigger than the R-11,” Yoneyama says, “but we tried not to make it look too bulky.”

Although the size difference between R-11Sq (above) and R-11 (below) is obvious in comparison, each muffler looks the right size when fitted on a bike.

The new R-11Sq series are initially available as slip-ons for GSX-R1000, GSX-S1000/F, YZF-R1/R1M and Ninja H2. More releases are expected in the future, so big-bike riders should stay tuned. The R-11Sq will no doubt become another flagship muffler of Yoshimura Japan.