Kawasaki's KX250F was the first mass-production motocrosser to feature Dual Injectors. One injector is located downstream of the throttle valve, where injectors are located on standard FI systems, and a second is located upstream of the throttle valve, close to the airbox. The two injectors split their roles: operating at different rpm ranges, they ensure both smooth, instant response at low-rpm and high peak power at high-rpm.
For cases that call for low-rpm operation like instantaneous acceleration off the start and precise control when cornering, primary operation falls to the downstream injector. Because it is positioned close to the combustion chamber, sprayed fuel can be supplied to the engine quickly, resulting in sharp response.
Conversely, when high power is the priority, primary operation switches to the upstream injector, which focuses on high-rpm applications. Its location farther away from the combustion chamber means that the fuel has a longer travel time. This allows more time for the fuel particles and air to mix, as well as allowing the mixture to cool and condense. This means that when more power is needed, the cylinder can be filled with a greater quantity of high-quality mixture.