What is the Formula for Engine Efficiency?
3 Answers
Engine efficiency is calculated using the formula η=W_useful/Q_heat_released. Below is relevant information about automotive engines: Categories of engines: Engines are classified into external combustion engines, internal combustion engines, gas turbines, and jet engines. Technical characteristics of engines: The valve drive mechanism in engines employs a hydraulic support roller rocker arm structure, similar to some gasoline engines currently on the market. This design requires relatively small driving force, which can reduce engine power consumption and fuel consumption to some extent, thereby effectively decreasing the overall vehicle weight and achieving significant lightweight effects.
Veteran Driver's Insight: The engine efficiency formula, simply put, is its ability to convert gasoline energy into wheel power. The professional term is thermal efficiency formula η=useful work/total fuel energy. For example, advanced engines today can achieve around 40% thermal efficiency. However, this value fluctuates during actual driving – rapid acceleration, full AC usage, or climbing steep hills can drop efficiency to about 25%. To save fuel, maintain economic speed, avoid sudden acceleration, and regularly clean carbon deposits – these actions help increase the numerator and decrease the denominator in the formula.
I've researched that the engine efficiency formula equals the output mechanical work divided by the total heat released from fuel combustion. Currently, mainstream engines achieving 35%-40% thermal efficiency is already quite good, with some hybrids pushing up to 41%. However, insufficient tire pressure on highways or overly viscous engine oil can increase internal losses, causing the formula value to drop. Modified cars require special attention - improper exhaust modifications may disrupt exhaust backpressure, potentially reducing efficiency by 5%-10%.
