Modern electronic fuel injection consists essentially of a pressurized fuel source, a solenoid valve and an electronic controller. The amount of fuel delivered to the engine is determined by the amount of time that the solenoid valve is open. It is up to the electronic controller to determine the engine's fuel needs and tell the solenoid valve when to open and when to close. This solenoid valve is commonly called a fuel injector. The amount of time that the injector is open is called the fuel pulse width. 

Fuel Injection 
Fuel is picked up from the fuel tank through a supply line. The fuel is passed through a fuel filter and delivered to the fuel pump. A positive displacement electric fuel pump then pressurizes the fuel. The pressurized fuel circulates past the two fuel injectors, then goes to the fuel pressure regulator. The pressure regulator returns fuel to the fuel tank via the fuel return line as required to maintain at a constant pressure the fuel supplied to the injectors. The constant flow of fuel provides cooling to the fuel pump and clears any tendency for vaporlock in the fuel system. 
Both injectors feed each cylinder. There are two injectors for the sake of fuel flow, not because there are two cylinders. The MCU determines which cylinder is breathing, and fires the injectors to provide fuel to that cylinder. Since the MCU knows which cylinder is breathing, the mixture for each cylinder can be individually adjusted. Injecting fuel only when the intake valve is open eliminates fuel puddling in the intake tract and provides crisp response and good fuel atomization. 
This fuel injection system lies somewhere between what is called a "throttle body injector" and what is called a "port style injector". Unlike throttle body injectors (pressure carburetors), the injectors in the WhiTek system are located downstream of the throttle plate and do not impede the airflow. Although the injectors are not mounted in the intake ports, the injectors are so close to the intake valve that the system functions like port injection.

Ignition 
Two separate transistorized ignition systems exist in the control system. They are intended to each drive their own spark coil, providing a single-fire capability. The two coil leads may be connected together to drive a stock coil double-fire, like a normal Harley ignition system. The ignition timing is extremely adjustable. Any desired "curve" can be achieved. The timing curve is actually a timing map, since the spark timing is a function of both the engine RPM and the throttle position. The curve that results is smoothed between the adjustment points, so that there are no abrupt jumps in the spark timing.

Electronic Controller 
The Master Control Unit (MCU) consists of a digital computer, analog amplifiers (for reading sensors), power output section (pump, injector and spark coil drivers), power supplies (conditioned power for computer and sensors), digital input/output (for communicating with the control/display unit), and a serial port (used primarily in factory testing).

Control/Display Unit  
This consists of an alphanumeric Liquid Crystal Display (LCD) and three push-buttons. The system is controlled and the engine's parameters and settings are monitored from this unit. The LCD is backlit (to be visible at night) and temperature compensated (to keep display contrast constant as the ambient temperature changes). The unit is splash proof, by virtue of using sealed push-buttons and sealing the display window against dust and moisture. Washing the unit or riding in a heavy rain will not affect it. The unit is not waterproof. Do not direct pressurized water at it.

Adjusting 
The system is adjusted from the control/display unit. The concept behind using the control/display unit is this: Pressing the top (T) or bottom (B) buttons steps through choices, nothing happens except that the display changes. Pressing the middle button (M) causes something to happen.

Fuel Mixture 
Mixture can be controlled in a number of different ways. The amount of fuel that is injected during each intake stroke is primarily controlled by the Mixture Map. Changes to fuel can be made by directly altering the entries in the Mixture Map. This is seldom done, since there are default maps to choose from that fit most needs. More commonly, the mixture is adjusted from the Tuning submenu, where changes are easily made in a fashion that more closely relates to carburetor tuning techniques. Here, the mixture can be adjusted for the equivalent of changing the main jet, the midrange jet, and the idle mixture.

Spark Timing  
Spark timing is controlled in the same fashion as is the mixture, except that the map entries control the spark timing. This allows for spark timing that varies with engine load and provides an extremely adjustable spark timing "curve." The default timing maps available are highly developed, so spark timing adjustments are normally done from the Tuning submenu, where the overall timing is easily changed.