Rockstar Makita Suzuki's Tommy Hayden leads the AMA Pro American SuperBike field this past August at Virginia International Raceway. Team Cycle World Attack Performance Yoshimura Suzuki rider Eric Bostrom (32) qualified on the front row of the grid. He finished seventh on Saturday and crashed out on Sunday.
CW Dynojet rear-wheel dyno, and I personally conducted the runs following the same procedures that are standard for all of our dyno tests. Stanboli attended the test, as did representatives ofYoshimura and LeoVince, and all involved were able to make fuel-mapping adjustments to the MoTeC engine-management system as needed based on 02 readings taken by Dynojet's wide-band exhaust-gas analyzer.
Considering the substantial differences in the two systems' designs, the end results were remarkably close, and both even produced smooth, streetbike-quality torque curves. With the Yosh exhaust—a 360-degree, 4-into-l system—the 1000 spun out 182.14 peak horsepower at 13,130 rpm (17.54 hp and 1530 rpm more than our bike's output when stock) and 78.66 ft.-lb. of torque at 10,810 revs. The LeoVince exhaust—a 4-into-2 system with 180-degree header-pipe mating—managed 180.86 hp at 12,785 rpm, a mere 1.28 horses short of the Yosh system's numbers and at a marginally lower engine speed, but with a virtually identical torque output of 78.63 ft.-lb. at 10,775 rpm.
Really, the biggest discrepancies occurred down in the 4000-to-6000-rpm neighborhood, where the Yoshimura system out-torqued the LeoVince by more than 6
ft.-lb. On a streetbike, that differential might be meaningful; but on a racebike that never dips down to that rpm level once it's off the start line, it's inconsequential. For all roadracing intents and purposes, the end result was a toss-up.
This seemed to assuage Yoshimura's concerns about the engine's power output with an "unfamiliar" exhaust, yet it also allowed Stanboli to maintain his close association with LeoVince. And as the bike has proven on-track in its first three outings at Mid-Ohio, Laguna Seca and Virginia International Raceway, it is competitive. Very much so.
Balance achieved. —Paul Dean
At its best, professional racing is a balancing act. On one hand, a race team tries its mightiest to do everything possible to win, but it also has sponsors and supporters whose needs must be met. And often, those needs end up in direct conflict with one another.
Such was the case with the Team Cycle World Attack Performance Yoshimura Suzuki AMA Pro American SuperBike. Our engine provider, Yoshimura Racing, wanted us to run the exhaust it had developed on the company's GSX-R1000 race motors; it was, in fact, the same system that four-time 2010 SuperBike winner Tommy Hayden has been using on his Yoshimura Suzuki. But our bike's builder, tuner and crew chief, Richard Stanboli of Attack Performance, has a long-standing relationship with LeoVince, so he was strongly motivated to use its exhaust. Stanboli was convinced that the LeoVince system would be fully competitive, while the Yosh people were worried that the Gixxer might not make full power with an exhaust they had never tested. It wasn't quite a Mexican standoff, but both parties had legitimate concerns.
In an effort to resolve the matter, we conducted a thorough dyno test of the racebike engine using both exhaust systems. To ensure fairness and allow the resultant numbers to be comparable to those we normally publish, we used the cycleworld.com/cwsb
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