What does the speed ratio of a car mean?
2 Answers
The speed ratio of a car refers to the transmission ratio, which is the ratio of the rotational speeds between the front and rear transmission mechanisms in the vehicle's drivetrain. There are two types of transmission ratios in a car's drivetrain: the speed ratio of the main transmission (final drive) and the speed ratio of the gearbox. In the same vehicle model, the speed ratio of the main transmission is a fixed value, while the speed ratio of the gearbox varies depending on the gear used. The speed ratio data for various types of vehicles can be found in the vehicle performance manual. When the minimum transmission ratio is too small, the car will operate under heavy load, resulting in poor acceleration and possible noise and vibration. Conversely, if the minimum transmission ratio is too large, fuel economy will suffer, and the engine will produce more noise at high speeds.
The gear ratio is essentially the transmission ratio in our cars, which, to put it simply, defines the relationship between how fast the engine spins and how fast the wheels turn. For example, when driving a manual transmission car, shifting into first gear feels like a high gear ratio—the engine revs hard, but the car doesn't move very fast, making it particularly powerful for climbing hills. In higher gears, the gear ratio decreases, allowing the car to glide swiftly while saving fuel. Choosing the right gear ratio has a significant impact on daily driving. For instance, using a low gear ratio on the highway consumes more fuel, but in city traffic, a high gear ratio may lack power. Most modern cars have automatic transmissions that adjust the gear ratio in real-time, but it's still essential to understand the basics. This knowledge helps when selecting a suitable car model, like SUVs, which often feature high gear ratio designs for off-roading or heavy loads. Over time, experienced drivers naturally grasp this trick—it directly affects both driving experience and fuel efficiency, so don’t overlook these small details!
