What is the typical RPM when a car reaches 120km/h?
2 Answers
When a car reaches 120km/h, the RPM is typically between 2500-3300, depending on the engine displacement and the manufacturer's power tuning. The relationship between RPM and speed, as well as influencing factors, are as follows: Relationship between RPM and speed: Generally, the higher the engine RPM, the higher the car's speed, showing a proportional relationship. The specific calculation formula is: Speed = RPM × Gear Ratio × Tire Circumference. Influencing factors: Besides RPM affecting speed, the gear ratio of the transmission and the tire circumference also influence speed. Additionally, friction and air resistance are significant factors. It's worth noting that once the engine reaches its rated power, even if the RPM increases, the speed will not increase because the onboard computer will cut off the fuel supply.
There's actually no standard answer to this question; it largely depends on what car you're driving. I've driven many cars and found significant differences between manual and automatic transmissions. For example, in an old 5-speed manual Volkswagen Sagitar, the RPM can soar to around 3100 at 120km/h, with the engine buzzing loudly. But in an 8AT BMW 3 Series at the same speed, it's only 1800 RPM, making the cabin as quiet as a library. Small-displacement cars like the 1.5L Nissan Sylphy often exceed 3000 RPM, while a large-displacement V6 Audi A6 might only be slightly over 2000 RPM. The number of gears in the transmission makes a big difference—cars with 9-speed transmissions clearly run at lower RPMs. The other day, I drove a friend's CVT Nissan Qashqai, and the tachometer seemed glued to 2200 RPM without budging. If you notice the RPM suddenly 500 higher than usual, it's likely the transmission isn't upshifting or the clutch is slipping, and you should get it checked immediately.
