Will the Vehicle Maintain a Constant Speed Without Pressing the Accelerator?

[EmersonFitz]

If the accelerator is not pressed, the vehicle will not maintain a constant speed. If the accelerator pedal is released during driving, the speed of the motor vehicle will decrease. The movement of the vehicle is directly controlled by the accelerator pedal, and maintaining a constant speed can result in relatively lower fuel consumption. Throttle, also known as the accelerator, refers to the control device that regulates the engine's power (thrust). In piston aircraft engines, the throttle controls the carburetor's throttle opening to adjust the cylinder's weight, thereby determining the engine's output power. In gas turbine engines, the throttle controls the fuel flow measured by the fuel regulator, thus determining the thrust generated by the engine. To maintain a constant speed in a motor vehicle: The vehicle's cruise control system needs to be activated to keep the vehicle moving at a constant speed. Once the cruise control system is engaged, the vehicle will maintain a constant speed without the need to press the accelerator pedal. This is particularly suitable for long-distance driving and travel, effectively reducing driver fatigue. Principle of the Cruise Control System: The system mainly consists of a control switch, a control unit (cruise computer), and a servo (actuator). Simply put, the cruise control system works by the cruise control unit comparing the pulse signals from the speed sensor with the set speed and then adjusting the throttle opening to increase or decrease, ensuring the vehicle maintains the set speed. For example, when the vehicle is going uphill and the speed drops, the pulse signals from the speed sensor decrease, and the control unit will send a command to the servo actuator to open the throttle at an appropriate angle to maintain the speed. Conversely, when going downhill, the throttle opening will be reduced. Additionally, the driver can manually accelerate, decelerate, or resume a memorized speed by operating the control switch. The cruise control system can be deactivated by pressing the brake pedal or clutch pedal or by turning off the control switch. Advantages of Constant Speed Driving: The benefit of maintaining a constant speed in a motor vehicle is that it provides excellent fuel economy, but it also requires finding an appropriate speed range. The optimal constant speed interval for a motor vehicle is between 80 km/h and 110 km/h, primarily determined by the engine's characteristics.

[SanCody]

When you don't press the accelerator, the car usually doesn't maintain a constant speed; it gradually slows down. This is mainly because the engine produces a small resistance when idling, called engine braking, which is like having a small brake pulling you. Combined with the resistance from wind and road friction, the entire car gradually slows down. I've driven many cars, from older models to newer ones, and unless the cruise control system is activated, releasing the accelerator on a flat road will also result in a gradual speed reduction. Different cars behave differently: manual transmission cars feel this deceleration more noticeably because the mechanical structure of the gearbox is at work; automatic transmissions are smoother due to electronic control. At high speeds, air resistance is greater, leading to faster deceleration; on low-speed city roads, deceleration is relatively gentler. In short, if you want to drive at a constant speed, it's best to press the accelerator slightly or use the cruise control function, which is both convenient and fuel-efficient. Car designs are quite ingenious, and well-tuned idle speeds can reduce that jerky feeling.

[FranciscoFitz]

As a driver who frequently takes long-distance trips, I can tell you: when you don't press the accelerator, the car won't maintain a constant speed; it will start to decelerate, especially on mountain roads or slopes, where it noticeably rolls downhill. I remember trying this on the highway last time—within less than half a minute after releasing the accelerator, the speedometer dropped by several kilometers. This is due to the resistance generated by the engine idling, somewhat like being dragged by a low gear. Modern automatic transmission cars decelerate more gradually on flat roads, but overall, speed still depends on your accelerator input. If you want to maintain a steady speed, cruise control is a lifesaver—just press a button and you won't have to worry. In daily driving, practicing coasting techniques can save some fuel, but don't expect the car to balance itself. Vehicle conditions like tire wear also affect this—proper tire pressure makes deceleration smoother. In short, for safety, don't rely on coasting to maintain speed; active control is the way to go.

[Brenda]

Maintaining a constant speed without pressing the accelerator is quite elusive; most of the time, the car will decelerate, with the engine idle becoming a source of resistance. In my years of experience, this varies by car: older manual transmission cars exhibit strong jerking and rapid speed loss when the accelerator is released; newer automatic transmission cars are smoother but still slow down gradually. On a flat road, releasing the accelerator might approximate a constant speed briefly, but wind resistance and tire pressure make it unstable. I recommend paying attention to feedback while driving: at low speeds, it feels like lightly tapping the brakes, while at high speeds, it's like gliding. Proper car maintenance can reduce such issues, such as cleaning the throttle body to improve idle efficiency. In short, maintaining a constant speed relies on throttle adjustment and control.