What is the relationship between torque and horsepower?
2 Answers
Torque and horsepower are both important indicators for measuring car performance. Under fixed power conditions, there is an inverse relationship between car torque and engine speed—the faster the speed, the smaller the torque, and vice versa. This reflects the vehicle's load capacity within a certain range. Like horsepower, car torque is one of the main indices of an engine, influencing performance aspects such as acceleration, climbing ability, and suspension. Horsepower is a crucial parameter for measuring engine performance and can be converted into power, where 1 horsepower = 1 HP = 0.735 kilowatts. Horsepower indicates how quickly work is done and is related to speed, while the ability to pull a certain load is related to torque. For example, if Engine 1 has a power of 110 horsepower, a small displacement, and a maximum torque of 140 Nm, while Engine 2 has a power of 90 horsepower, a large displacement, and a maximum torque of 240 Nm, Engine 1 has higher horsepower and smaller displacement and torque compared to Engine 2. Therefore, Engine 2 can pull more cargo than Engine 1. Higher engine power inevitably leads to higher fuel consumption, increased emissions, and pollution. For consumers and the environment, blindly pursuing horsepower or power is one-sided. In reality, the reason some domestic and international models can offer a wide price range to consumers is due to the variety of engines, transmissions, powertrains, and electrical systems provided by manufacturers. However, using a high-performance engine will significantly increase the price of the car.
I've driven quite a few cars, and I feel that torque is like the explosive power of an engine, giving the car instant acceleration from a standstill, such as when starting or climbing a hill—it's particularly powerful with noticeable back-pushing force. Horsepower, on the other hand, is responsible for sustained high-speed running, like overtaking on the highway or maintaining fast speeds. Simply put, the two have a mathematical relationship: horsepower is roughly equal to torque multiplied by RPM divided by 5252. At an engine speed of 5252 RPM, the two values coincide. In actual driving, a car with high torque feels more exhilarating for city commuting, while a high-horsepower car is more fuel-efficient for long-distance travel. To choose a good car, I look for balance—for example, an SUV with higher torque is better for off-roading, while a sedan with higher horsepower is more suitable for speeding.
