CW: Air drag coefficient (or wind drag coefficient).
Generally speaking, you can know whether the horsepower of a car is strong or not from the number of cylinders and displacement of the car. Other things being equal, the higher the power, the higher the speed. The greater the torque, the greater the traction of the car. Sail's power is 66kW/5600rpm and its torque is 128nm/2800rpm. That is to say, when the engine speed reaches 5600 revolutions per minute, the maximum output power is 66 kilowatts; When the engine speed reaches 2800 rpm, the maximum output torque is 128 Nm. Why is the maximum power and torque of the engine not at the same speed? Because there is a minimum stable working speed after the engine is started. With the continuous improvement of engine speed, the output power and torque of the engine also increase. When it reaches 2800 rpm, the torque reaches the maximum, but the engine power does not reach the maximum at this time. If the engine speed increases, the torque decreases and the power continues to increase until the maximum power is reached. What do you think if you find that the maximum power and torque of the two cars are very close when you choose to buy a car, but the corresponding speeds are different? This situation shows that the acceleration characteristics of the two cars are different to some extent. When the maximum torque of the car is at low speed, it shows that the car has good climbing acceleration and is easy to overtake; When its maximum torque appears at a high speed, it shows that the car has a large reserve power. The latter has a low load rate during driving, so the economy is poor. Generally, such an engine will be used in a large RV.
Wind drag coefficient is a parameter rarely mentioned by ordinary consumers when choosing a car. When driving at low speed, the negative influence of air resistance on fuel consumption can be ignored, but with the increase of vehicle speed, the engine power consumed by the vehicle to get rid of air resistance will suddenly increase, and the power consumption has a cubic relationship with vehicle speed -w = cv3 (w is the power consumed by wind resistance, c is the wind resistance coefficient, and v represents vehicle speed). According to the test, when a car is driving at a speed of 80 km/h, 60% of the fuel consumption is used to overcome the wind resistance. It can be seen that the higher the vehicle speed, the closer the relationship between drag coefficient and fuel consumption, even if the drag coefficient is reduced by 1%, it will play a key role.