Eddy current dynamometers are electromagnetic load devices. The engine or vehicle being tested spins a disk in the dynamometer. Electrical current passes through coils surrounding the disk, and induce a magnetic resistance to the motion of the disk.

Varying the current varies the load on the engine.

Due to the fact that Eddy current dyno’s can be controlled throughout the entire load range they allow engine tuners to do a much beter job of the tuning process.

A dynamometer is a load device which is generally used for measuring the power output of an engine. Several kinds of dynamometers are common, some of them being referred to as “breaks” or “break dynamometers”: dry friction break dynamometers, hydraulic or water break dynamometers and eddy current dynamometers.

The dynamometer applies a resistance to the rotation of the engine. If the dynamometer is connected to the engine’s output shaft it is referred to as an Engine Dynamometer. When the dynamometer is connected to the vehicles drive wheels it is called a Chassis Dynamometer.

The force exerted on the dynamometer housing is resisted by a strain measuring device (for example a strain gauge).

Dyno tuning is the careful manipulation of mechanical or electronically controlled inputs to the engine while the vehicle is being driven on a chassis dyno or the engine is attached to an engine dyno.

The most popular form of dyno tuning is done on a chassis dyno because it does not require removal of the engine.

Dyno tuning is done to achieve maximum engine efficiency. When engine efficiency is maximized fuel consumption during cruise is optimized and  horsepower during full throttle operation is increased to it full potential.

A stand alone engine management system or after market ECU is an engine management system that is not OEM and one that can be fully manipulated via computer based software to control all engine functions.

ECU stands for engine control unit and it controls engine functions such as engine timing, fuel input, cold start fueling, fuel pump control, detonation detection and control, cooling fan switching and many other functions.

ECU’s are also referred to as:

EMS = Engine Management System
PCM = Power Control Module

A Reluctor Interface is used where an engine is equipped with magnetic sensors. It converts the magnetic signal to a signal that looks to the Engine Management System (EMS) like a Hall signal.

A Hall signal is produced by a Hall effect sensor and it looks in its basic form like an on-off signal or square wave.

Fuel from the fuel rail, under pressure, is sprayed in a very fine miss from the tip of the injector. To achieve this, a current must flow through the fuel injector electrical field coils. Contrary to popular belief, this is NOT done by sending power to the injector. Fuel injectors are normally fed power whenever the ignition key is on, but the circuit is not completed and therefore the injector is still close. The computer controls the ground side of the circuit. When the computer provides the injector with a ground, the circuit is completed and current is allowed to flow through the injector. This energizes an electromagnetic coil inside the injector, which pulls a sealing mechanism such as a pintle, ball, or disc away from its seat. This makes it possible for fuel to flow through the injector and into the engine. When the computer removes the electrical ground to the injector, the electromagnetic coil becomes demagnetized and a spring forces the pintle, ball, or disc shut to cut off fuel flow. Even at an engine speed of just 1000 RPM, this is done hundreds of times per minute.

A fuel injector is an electronically controlled valve that consist of a body that houses an electromagnetic coil and a sealing mechanism such as a pintle, ball or disc that is either fully open or fully close. The amount of fuel injected is determined by how long the pintle, disc or ball is removed from its seat.  Fuel Injectors are either fully open or fully closed and the  period the valve is fully open is measured in millionths of a second.

Injectors have the finest tolerances of any mechanical part on the engine.