Technical Information Air Inlet System

Subthrottle Control System

The ZR1000-A1 ~ employs large bore throttle bodies to increase power output. However, sudden changes in throttle opening can cause hesitation and jerky throttle response with a single butterfly valve in a large bore. Therefore two throttle valves are placed in each inlet tract, the main throttle valve located closest to the cylinder and a subthrottle valve placed further up the inlet tract. The main throttle valve is operated by the rider when the throttle grip is turned clockwise or counterclockwise, while the subthrottle valve is operated by a stepping motor controlled by the ECU. The subthrottle valve automatically adjusts air inlet to more precisely match engine demand, so that when the main throttle is opened quickly there is no hesitation or jerky response.

The subthrottle valves allow the fuel injection system to provide smooth throttle response, similar to that of a constant velocity carburetor, no matter how quickly the throttle is opened.

A. Main Throttle Valve D. Vacuum Piston

B. Subthrottle Valve E. Inlet Air

C. Throttle Valve

A. Main Throttle Valve D. Vacuum Piston

B. Subthrottle Valve E. Inlet Air

C. Throttle Valve

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