![]() Because of the conventional injectors' proximity to the intake valves, the CBR600RR's throttle response is razor-sharp below 5500 rpm. At higher engine speeds-5500 rpm and above-the showerheads deliver fuel just a fraction of an instant before the main throttle-body-mounted injectors do. On the RR, this advanced system utilizes a set of four 12-hole fuel injectors mounted in new, larger 40mm throttle bodies, plus another full set of 12-hole injectors mounted high in the roof of the airbox. The same concept drove the design of the CBR600RR's fuel delivery, its Dual Stage Fuel Injection System (PGM-DSFI). Honda incorporated such a system on its RC45 Superbike machines, and more recently on the world-championship-winning RC211V. It also significantly cools the airflow, resulting in a denser charge that yields more horsepower. Its greater distance from the cylinder provides extra vaporization time, plus exposure to the turbulent mixing of the intake flow. This so-called showerhead injector, positioned over the open end of each velocity stack, injects fuel at higher rpm. In Formula 1, the successful answer was to place a second injector as far from the intake valve as the length of the intake tract would permit. The RR's engine demands at that rpm exceed the capabilities of conventional fuel delivery systems, however sophisticated-there's just not enough time. ![]() ![]() More importantly, at 15,000 rpm there's only 4 milliseconds for the fuel squirting out of the Denso injectors to vaporize and combine with incoming air into a combustible mixture fuel droplets simply do not burn well. That means the valves will open and close 31 times before the rider can even blink. At 15,000 rpm, each intake and exhaust valve of Honda's CBR600RR opens and closes 125 times a second, or 8 milliseconds. The blink of an eye takes about one-quarter of a second, or 250 milliseconds. ![]()
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