New patents filed by Kawasaki shows a four-cylinder supercharged unit that features two sets of injectors per cylinder, one located in the conventional location – within the throttle body and another pointing into the top of the combustion chamber.

Direct injection was first used in cars using a rudimentary system since the 1950s. But only recently has the motorcycle manufacturers have started experimenting with the method, mostly due of ever-tightening EU emissions regulations.

Using just direct injection on a motorcycle engine is unlikely to work with high-revving engines, hence why Kawasaki is opting for a hybrid method to get most from both direct and port injection.

Direct injection has one other advantage that it keeps the combustion chamber of the engine cool, which helps to prevent knocking or abnormal combustion. A direct-injection engine can also more accurately monitor the air/fuel mixture entering the engine, as the fuel is squirted in neat, not mixed with air before entering the engine. Also fuel can be added at different points of the combustion cycle. In comparison, I port injection engine can only add the fuel (and the air) when the intake valves with allow.

Alas, there sure is one disadvantage. A conventional port injection engine has a cleaning effect on the valves, helping to slow the build-up of carbon deposits. The air and fuel mixing in the throttle body also has a cooling effect on the top end of the engine, cooling the head and intakes a little. This cooler area of the engine helps to keep the air drawn in cooler too. Cooler air means denser air with more oxygen molecules and that makes for a bigger bang within the combustion chamber.


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