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Before we start, let us understand the intake system of an automobile. 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 outside. The amount of air and fuel mixture going inside the engine is controlled by a throttle valve or a butterfly valve.
The throttle valve is included in a carburettor. In an MPFI engine, the throttle valve or butterfly valve is a separate unit. The throttle valve which opens and closes to adjust the air-flow into the engine is controlled by a cable connecting the accelerator pedal. Nowadays, most cars do not have that cable. Instead, the throttle valve is electronically actuated by the ECU (Electronic Control Unit) using inputs from the accelerator pedal. This system is known as Drive-By-Wire. In motorcycles, it is called Ride-By-Wire.
Now that you know what Drive-By-Wire or Ride-By-Wire is, let us go into a bit more detail. Also called Electronic Throttle Control, the system was first introduced in the 1988 BMW E32 7-Series. BMW referred it to as EML back then. EML stands for 'Electronic Throttle Control System' in German. Eventually, the system slowly filtered down to more brands and more cars. The 2006 Yamaha YZF-R6 was the first motorcycle to pioneer the Ride-By-Wire system.
Drive-By-Wire Working In Detail
As told earlier, 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 (a body which moves under the influence of an external element, most probably an electronic unit). The actuator, in turn, opens the throttle valve or butterfly valve to a specified amount. The actuation process is carried out by a servomotor. The inputs to the DC servomotor come in different 'duty cycles'. Duty cycles refer to the amount of time the servomotor needs to be run. Or to be simple, less the running-time or duty cycle, less the valve opening and vice-versa.
Integral to the Drive-By-Wire system is the Throttle Position Sensor (TPS). 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.
- Drive-By-Wire eliminates the need for any mechanical linkages and hence aid in weight savings.
- Today's cars come with a host of safety systems such as Electronic Stability Control (ESC), Adaptive Cruise Control and Hill-Assist, all functioning with the inputs from Drive-By-Wire.
- In some cars and motorcycles, the accelerator becomes tighter to use with time. This occurs mainly due to the wear of the throttle cable. Drive-By-Wire offers fatigue-free driving.
- Drive-By-Wire system is so programmed that the car gives a good balance between performance and fuel efficiency on all throttle inputs.
- Drive-By-Wire also ensures that an amateur driver doesn't lose control easily if he/she floors the car hard.
- Drive-By-Wire is an expensive addition to the engine and is also an expensive replacement.
- Being an electronic system run by a set of codes, a slight change (highly unlikely though) in the program architecture might invite potential hazards such as an uncontrollable acceleration.
- Purists would not prefer it as most Drive-By-Wire systems lack the ‘raw' feel of accelerating the car. Most Throttle-By-Wire systems retardthe initial acceleration of the car to a certain extent. 'Throttle Boosters' are employed to prevent this.
- Being an electronic component, it cannot be worked on manually. Engine builders and enthusiasts love to work on their car and with Drive-By-Wire, they cannot manually adjust the throttle response easily.
Other ‘By-Wire' Systems
With time and advancement in technology, a lot of cable-operated systems have been replaced by electronic controls. Here are some examples:
The system eliminates the need for hydraulic pressure to actuate the brakes. Or, such braking systems do not need a brake fluid to apply the brakes. The brakes are applied electronically.
Almost all automatic transmissions employ this. The Park, Reverse, Neutral and Drive modes are engaged by electronic inputs and not by a cable. Coming under it, Park-By-Wire engages the parking brake or handbrake in automatic cars, by electronically locking the transmission.
This steering system uses motors and actuators on the car's front axle to turn the wheels. It also eliminates the linkage systems in between the steering and the front wheels. It is different from Electronic Power Steering (EPS).
EPS also has the elements of a conventional steering unit. An electric motor is connected to the steering column or the steering gear. Inputs from the steering wheel are converted to actuator motor outputs, which in turn rotates the steering gear or turns the steering column.
Used in aircrafts and spaceships, the system replaces the cable-operated rudder and flap movements, with electronic actuators. Input signals from the ‘yoke' (steering wheel-like control system in a plane) and the ‘side stick' (joystick in a plane) are used by motors on the wings and tail to control the flight direction.
Thoughts On Drive-By-Wire System & Throttle Cable System
With the advancement in automotive technology, conventional mechanical parts are being replaced by electronic components. Though these electronics offer better efficiency and adaptability, they are slowly pulling out the character of an automobile. A car or motorcycle racer from the ‘80s or ‘90s or even the early 2000s, will never prefer Drive-By-Wire. For them, releasing the clutch and adjusting the throttle for the right launch is what matters.