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Power Sports and Electronic Fuel Injection Glossary


To ensure comparable emissions data, the temporal progression curves for the speeds and forces acting on the vehicle during the simulated cycle on the chassis dynamometer must precisely coincide with those for highway operation.


A temporary restriction in a carburetor throat that reduces the flow of air and enriches the fuel-air mixture to aid in starting the engine.


A mechanism that uses plates coated with a high-friction material to transfer power from the engine to the drive train. Used when changing gear ratios during acceleration. Clutches are also used to isolate rotating and non-rotating components. Clutches can allow slip between components to reduce shock loads between rotating and stationary components. Manual transmission vehicles use a clutch to transfer power from the gearbox to the wheels. Air conditioning compressors use clutches as well.


Originally, a motorcycle that has had all non-essential parts removed (or chopped) to make it lighter and faster. Today, this name generally applies to custom built motorcycles that may have a rigid frame (no rear suspension), an extended fork, and a stretched or elongated appearance.


A motorcycle built to resemble and function like a Harley-Davidson motorcycle without actually being a Harley-Davidson motorcycle (the vehicle title will identify it as something other than a Harley-Davidson).


Depending upon the engine temperature, the cold-start valve injects an additional quantity of fuel for a limited period of time during starting.


The space remaining at the top of the cylinder when the piston is at the top dead center position where the fuel-air mixture begins to burn. Since most of the air-fuel mixture's combustion takes place in this space, its design and shape can greatly affect the power, fuel efficiency, and emissions of the engine.


Under certain conditions, combustion in the spark-ignition engine can degenerate into an abnormal process characterized by typical 'knocking' or 'pinging' sound. This undesirable combustion phenomenon marks the outer limits of ignition timing advance, and thus, at the same time, defines the boundaries of power-generation potential and efficiency. It occurs when fresh mixture pre-ignites in spontaneous combustion before being reached by the expanding flame front. During an otherwise normally initiated combustion event, the pressure and temperature peaks created by the piston's compressive force generate self ignition in the end gas (remaining unburned mixture).


All injectors in a CI (Continuous Injection) system spray at the same time and the same amount. There is no timing as with mechanical injection.


While the two-state sensor can only indicate two states - rich and lean - with a corresponding voltage jump, the wide-band sensor monitors deviations from lambda=1 by transmitting a continuous signal. In other words, this wide-band sensor makes it possible to implement lambda control strategies based on continuous instead of dual-state information.

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