Throttle By Wire

An Internal Combustion Engine (ICE) needs air and fuel for initiating combustion inside the cylinders. Fuel is supplied by injectors or a carburettor, Air is taken from the air intake and the flow of fuel into the engine's combustion chamber is controlled/regulated by the throttle, also known as butterfly valve.The throttle valve which opens and closes to adjust the air-flow into the engine is controlled by a cable connecting the accelerator pedal.

           

                                       valve                                                        cable

The throttle cable has almost become extinct on today’s motor vehicle. The newer, drive by wire or throttle by wire technique was first used back in the year 1988 by BMW in its 7 series.BMW has named it EML which is abbreviation of a German term meaning Electronic Throttle Control.

Actually, what this technology does is it replaces the  mechanical linkage between the accelerator pedal and the throttle butterfly, which used to be via a cable or via rods and linkages by some sophisticated electronic control modules, sensors and actuators. This system is also referred to as Fly-by-Wire.Earlier the electronic throttle actuation or EML was based upon the option of becoming a production line ‘add on’ system. It utilised its own Electronic Control Module (ECM), without the requisition of additional hard wear (and programming) to the vehicle’s original ECM. This was achieved by inputting minimal data into the vehicle’s ECM via a serial link from the electronic throttle actuator’s separate control unit.

Today’s systems have a specific ECM that incorporates the necessary programming to facilitate the input signals from the throttle pedal potentiometers and signal outputs to the electronic throttle body.

Drive-By-Wire or Throttle-By-Wire eliminates the use of a cable for controlling the throttle valve. The accelerator pedal is connected to a potentiometer. The various positions of the pedal act as the potentiometer inputs. These inputs are received by the ECU.Based on the inputs, the ECU is programmed to run an actuator.The actuator, in turn, opens the throttle valve or butterfly valve to a specified amount. The actuation process is carried out by a servomotor. Throttle Position Sensor (TPS)  is integrated into the throttle by wire . The TPS sends the position signals of the throttle valve back to the ECU. The signals from the Throttle Position Sensor and the input from the potentiometer connected to the accelerator pedal, helps the ECU to perform the ‘throttling' with greater accuracy.

ADVANTAGES:

• No wear and tear of throttle cable.
• Eliminates significant amount of weight by eliminating the use of mechanical linkages.
• Safety features like ESC, Hill hold assist, and Adaptive Cruise Control system  take inputs from the throttle.
• Maintains control even if the driver floors the accelerator pedal.

DISADVANTAGES:

• Increases the cost.
• Costlier to replace/maintenance cost is higher.
• Throttle response can't be adjusted manually, which some people love to do.
• Leads to more energy consumption
• Delay in response from the engine.