WRIST: Ari Henning
MSRP (2011): $3999
MODS: JETT Tuning engine work
It’s hard to believe all those traces are from the same motor. This graph shows our CBR250R racebike project in its various states of development, from stock (red lines), to hopped-up with Leo Vince exhaust, K&N air filter and Bazzaz Z-Fi fuel module (green), to the “Production” and “Superbike” setups we have now. The blue traces show the engine’s output when the bike conforms to 250 Production class rules, with the airbox in place and pump gas running through the injector. The black line towering above everything else is with the airbox removed, a velocity stack installed, and VP T4 fuel ($12.79 per gallon; www.vpracingfuels.com) in the tank, as is permissible in the 250 Superbike class. The T4 is a more affordable high-octane alternative to VP’s U4.4 race gas that provides the detonation protection needed to safely increase compression and advance the ignition timing.
John Ethell at JETT Tuning (www.jetttuning.com) performed all the engine work on our Honda. He used our CBR250R as a test mule to develop a performance kit, and in the process blessed us with an additional 4.5 horsepower over stock. That number sounds small, but it amounts to a 20 percent increase in peak power. And look at that spread! The power curves follow much more desirable arcs now thanks to increased compression and altered cam and ignition timing, and Ethell even raised the rev limiter with a Power Commander unit he designed and is having manufactured.
With just the pipe, air filter, and Bazzaz unit the power fell off abruptly beyond 8200 rpm, but now the zenith is flatter and the power is sustained longer. Peak output with the airbox in place is 25.9 bhp at 8100 rpm, and remains within 0.5 bhp of that figure for 2000 rpm. The bike breathes much better through a velocity stack, and in Superbike trim the CBR puts down 27.5 bhp and remains strong all the way to the new 10,800-rpm rev limit. If that’s not impressive, I’ll eat a piston. I’ll detail the engine mods—and provide a full race report from the upcoming AFM event at Infineon Raceway—in the next installment.