Drive-by-wire is the common name for electronic throttle control. Traditionally, cars’ accelerator pedals are connected by cable to the throttle control on the engine. The relevance of DBW is that it takes the guesswork out of “stepping on it,” and calculates the appropriate throttle, based on traction, vehicle speed and engine speed. It’s called “drive by wire” because the gas pedal is no longer physically connected to the engine in order to function. Instead, it’s all electronic.
Electronic throttle control (ETC) is an automobile technology which severs the mechanical link between the accelerator pedal and the throttle. Most automobiles already use a throttle position sensor (TPS) to provide input to traction control, antilock brakes, fuel injection, and other systems, but use a bowden cable to directly connect the pedal with the throttle. An ETC-equipped vehicle has no such cable. Instead, the electronic control unit (ECU) determines the required throttle position by calculations from data measured by other sensors such as an accelerator pedal position sensor, engine speed sensor, vehicle speed sensor etc. The electric motor within the ETC is then driven to the required position via a closed-loop control algorithm within the ECU.
The benefits of ETC are largely unnoticed by most drivers because the aim is to make the vehicle power-train characteristics seamlessly consistent irrespective of prevailing conditions, such as engine temperature, altitude, accessory loads etc. The ETC is also working ‘behind the scenes’ to dramatically improve the ease with which the driver can execute gear changes and deal with the dramatic torque changes associated with rapid accelerations and decelerations.
The main benefit is that the car can control the throttle irrespective of the actual position of the accelerator pedal. This makes traction control, cruise control and stability control easer to manage, particularly for those cars that have these features.