Red Rocks: 2003 Cbr600rr!
RED ROCKS: 2003 CBR600RR!
ROUNDUP
VALENTINO Rossi, EAT your heart out! The new CBR600RR splits Honda’s middleweight offerings in two: The RR aims without compromise at performance, while the carryover CBR600F4i retains the traditional mix of qualities.
A new 600 is always a treat for sportbike enthusiasts because it closely links racing with production. Honda’s rich new source of technology is its brilliant V-Five MotoGP bike, the RC211V The top of the hot-selling 600cc class is a moving target, so advanced concepts must be re-engineered for the showroom.
Honda’s GP four-stroke makes its peak power above 16,000 rpm. The CBR600RR is not far behind, redlining at 15,000 rpm. Claimed max output-117 bhp at the crankshaft-comes at 13,000 rpm, 800 rpm higher than on the CBR600F4i. Why redline an engine 2000 rpm above its power peak when
rev limiters work so well? Racing gives the answer: Engines must pull past peak power when shifting is impossible or would cause delay. “Overrev,” the racers call it.
Cylinder dimensions are 67.0 x 42.5mm. Thanks to this short stroke, even at 15,000 rpm, piston speed remains a comfortable 4200 feet per minute. Production engines now thrive in what was once closed to all but factory racing engines.
The limit for valvetrain stability has been raised by use of dual nested springs on each of the 16 valves. This not only increases spring pressure, it also provides spring-to-spring friction damping to eliminate destructive high-speed wave action in the springs.
Lighter 12:1 pistons and pins offset what would otherwise be an rpm-driven 12 percent increase in bearing friction loss. Pistons have now shrunk to thin discs to carry the rings, with only vestigial skirts to stabilize them. As revs rise, piston weight must fall.
The faster an engine turns, the less time there is in which injected fuel can evaporate. To be ignited by spark, gasoline
must mix with air as vapor-fuel burn poorly. Multi-hole, laser-drilled injector nozzles help, but at 15,000 rpm there is only .003 of a second for evaporation. So even with its 12-hole Denso injectors, the RR’s engine needs assistance. Enter the GP bike’s system of twin injectors-one in the conventional position under the butterfly throttle valve, the other as far upstream as possible, suspended over the open end of each cylinder’s intake pipe. At lower rpm, only the bottom injector sprays into the 40mm throttle body, its closeness to the cylinder giving best throttle response. As the engine accelerates past 5500 rpm, the top injectors-called “showerheads”-chime in. Honda calls this Dual Stage Fuel Injection. A more mundane development is that cold starting is now implemented in software-no more choke on brisk mornings.
To permit use of a long, GPstyle top-braced swingarm, the new engine’s cases are 30mm shorter than before. At the same time, the rider is moved forward almost 3 inches. This forward weight shift increases the bike’s ability to accelerate rapidly without front wheel lift, despite the short 54.7-inch wheelbase. In the compact “Unit Pro-Link’’ suspension shared with the RC21IV, the top of the RR’s shock attaches to the swingarm and extends downward to linkage beneath. This vacates space above the swingarm; could that space in time be filled with an RC-like underseat gas tank? Although the CBR’s frame is black, its swingarm is natural aluminum to underline kinship with the RC-V
Any visual similarity is purely intentional. Both bikes have their fairing sides deeply cut away to reveal engine shape, and similar hot air ports pierce the fairing sides. Look into the fairing front and you see a Superbike-style radiator, filling the opening from top to bottom. When you make more power, you also make more heat.
Where does it all end? It never can. -Kevin Cameron
