Fuel Injected Motorcycles Know How, Know What

Motorcycle fuel injection uses what is called an "N Alpha" system, which is mapped injection. Manufacturers take an example of the engine, run it on a dyno at all different throttle levels and rpm, work out the correct fuel mixture for every condition, and then they make a map. They have all the N variables and the map connects those variables by supplying a particular amount of fuel and telling the injectors how long to stay open. Air is controlled by a butterfly valve. If you have a steel throttle cable, when you turn the throttle the cable physically pulls the throttles open. If you have a throttle-by-wire system, like those found on more modern motorcycles, turning the grip tells the computer what you want and it opens the throttles a certain amount. To burn the gasoline in an engine, it must first be mixed with air and then ignited with a spark. For many years, carburetors were the main device for this purpose, blending the air and fuel together to form a mist to be ignited. However, since they are mechanical in nature, carburetors are easily affected by the climate, so a more effective system was desired. With concern for the environment also growing, this presented a greater need for a system that would put out fewer emissions and deliver both better fuel efficiency and power. These needs led to the development of fuel injection systems, which are used by the majority of cars and motorcycles today. The fuel is sent through the injector at high pressure to atomize it into droplets just a few microns in diameter to increase the fuel’s surface area, and it is then sprayed into the intake passage through the tiny holes—usually 4 to 12—at the tip. There, it mixes with the air and is directed into the cylinder’s combustion chamber, where it is ignited to combust.