The dashed lines for rpm and countershaft speeds show the typical lag between the two as play in the gear dogs is taken up. The Ignition Interrupt Control System detects the difference as the engine increases speed while the countershaft doesn't, and issues a signal to reduce power momentarily. The solid lines indicate the typical speeds for each shaft with the system working.
Ignition Interrupt Control System
To improve the 1000's ride-ability, Honda concentrated on the all-important off/on throttle transition with a three-pronged solution to smoothing response. The addition of a slipper clutch reduces the tendency for chatter on deceleration, and the Idle Air Control Valve, first seen on last year's CBR600RR and incorporated into the '08 1000, reduces engine braking and eases the throttle's abruptness. The third aspect to improving the throttle transition is reducing driveline lash, which is addressed by Honda's Ignition Interrupt Control System. The transmission and its gear dogs are responsible for 50 percent of driveline play, and the system detects this lash by comparing crankshaft speed to countershaft speed. Any difference indicates the switch from deceleration to acceleration, and the ECU reduces power for up to 20 milliseconds-while the countershaft catches up to match the crankshaft's relative speed-to ease that transition. A different amount of interrupt is used for each gear, and the system is only active at 2500-6000 rpm; Honda reps indicate the setup is more for the street rider than for track use. It's an interesting and unique solution to a problem most manufacturers have addressed with electronically controlled butterfly valves in the throttle body, and the Honda CBRs are among the few sportbikes that retain a single, rider-controlled butterfly. The Ignition Interrupt Control System, using no new sensors or additional electronics and requiring only additional programming, potentially saves the weight and complexity of a secondary butterfly or more complicated ride-by-wire setup. It would seem an easy step from this system to extend the operating range and parameters to add rate-of-change traction control-again, no new sensors would be required-but a Honda representative pointed out that while implementing such a system would be relatively simple, the development time and costs to perfect it were prohibitive for this year's model.