Yoshimura has long been a performance innovator, and the latest gem from the company is a dual-outlet muffler for the RS-4 exhaust that turns it into the RS-4D. We are just starting to see these systems at the track.
The new muffler was developed in conjunction with the Rockstar Makita Suzuki Yoshimura race team. Since that team largely consists of multitime champ Ryan Dungey, you could say Yosh has good feedback to work with. Word on the dirt claims that dyno numbers aren’t greatly different for the dual-outlet muffler, but the response the rider feels is increased.
The increases in measurable power are that are shown on the dyno are all in the bottom and middle rpm ranges – where most humans spend time on a 450cc motocrosser. At the moment the RS-4D is available for the Suzuki RM-Z450, but models for the RM-Z250 and the Honda CRF250R and CRF450R are expected. For more information go to www.yoshimura-rd.com.
