Different cars have different engine RPMs (revolutions per minute) at the same speed because of variations in their gear ratios, final drive ratios, transmission types, tire sizes, and engine characteristics.
Here are the main reasons:
Gear Ratios:
Cars have different transmission gear ratios. A lower gear ratio results in higher RPMs at a given speed, while a higher (taller) gear ratio reduces RPMs.
Final Drive Ratio (Differential):
This ratio affects how many times the engine turns to rotate the wheels once. A high final drive ratio increases RPM at a given speed.
Transmission Type:
Manual, automatic, and CVT (continuously variable transmissions) behave differently. CVTs can keep the engine at an optimal RPM regardless of road speed, while manuals and automatics follow fixed gear steps.
Tire Size:
Larger tires cover more distance per revolution, which lowers engine RPM at a given speed. Smaller tires do the opposite.
Engine Design and Purpose:
Some engines are tuned to run efficiently at lower RPMs (like diesel engines), while high-performance or smaller engines may need higher RPMs for power delivery.
Example:
A sports car and an SUV both traveling at 100 km/h could have very different RPMs-one might be at 2,500 RPM while the other is at 1,800 RPM-due to differences in gear ratios, transmission design, and intended vehicle performance.
In summary:
Even at the same speed, how hard the engine is working (RPM) depends on how the car is engineered for performance, efficiency, or load capacity.
