Why Do Four-Cylinder Cars with the Same Displacement Have Different Horsepower?
3 Answers
Four-cylinder cars with the same engine displacement can have different horsepower outputs due to the two different operating conditions: naturally aspirated and turbocharged. Main Function of Turbocharging: Turbocharging increases the engine's air intake, thereby enhancing the engine's power and torque, making the car more dynamic. Horsepower with Turbocharging: When a turbocharger is installed on an engine, its maximum power can be 40% or more higher than without the turbocharger. This means the same engine can output significantly more power after being turbocharged. Taking the most common 1.8T turbocharged engine as an example, after turbocharging, its power can match that of a 2.4L engine while still maintaining a 1.8-liter displacement. In this scenario, the engine's horsepower is much higher than that of a naturally aspirated 1.8-liter engine.
The horsepower difference in seemingly identical four-cylinder engines primarily stems from engine tuning. As an engineer who frequently studies mechanical principles, I can confirm that engine power isn't solely determined by cylinder count. Factors like compression ratio settings, turbocharging systems, and ECU control units all play crucial roles. Manufacturers adjust these parameters based on vehicle positioning - sportier models receive higher horsepower through increased boost pressure or optimized air intake flow, while economy-focused family cars adopt conservative tuning prioritizing fuel efficiency and emission control, preventing overheating or excessive noise. Additionally, material strength (e.g., pistons and crankshafts) affects performance limits. Some engines employ lightweight alloys capable of sustaining higher RPMs, naturally yielding greater power output. Tuning also involves exhaust system optimization, where reduced backpressure unleashes additional horsepower. Ultimately, identical exterior appearances conceal vastly different internal designs, resulting in significant final horsepower variations.
My four-cylinder car has significantly less horsepower than my friend's similar model, which puzzles me. During daily commutes, I always feel it's a bit sluggish at startup. Turns out, manufacturers intentionally detuned the engine to save costs and fuel. Others might have added turbochargers or optimized combustion systems, resulting in stronger output. On car enthusiast forums, I've seen people even flash ECU software to boost horsepower. It also relates to the cooling system—better heat dissipation maintains higher performance. When buying a car, different configurations offer varying horsepower. The difference becomes obvious when overtaking on highways—higher horsepower cars are noticeably more agile and efficient, though fuel consumption increases slightly. It's a clever design that caters to different needs and budgets.
