What is the normal engine load?
3 Answers
The normal ratio for engine load is between 20 and 50. Below is relevant information about engine load: 1. Definition: The engine load rate, often simply referred to as load, is the ratio of the engine's effective power output at a given speed to the maximum effective power it can produce at the same speed. 2. Characteristics: Engines are broadly categorized into gasoline engines and diesel engines. Gasoline engines regulate load via the throttle valve, hence gasoline engine load characteristics are also known as throttle characteristics. Diesel engines adjust load by varying the fuel injection quantity, altering the air-fuel mixture composition through changes in fuel injection, thus diesel engine load characteristics are termed fuel adjustment characteristics. Since engine speed frequently varies, it is necessary to measure the load characteristics at different speeds to comprehensively evaluate the fuel economy of the engine under various speeds and loads. Engine load characteristics are measured on a test bench. Taking a gasoline engine as an example, after starting the engine, the throttle valve is gradually opened to its maximum while adjusting the load to maintain a stable speed. The engine's output power and fuel consumption are measured under these conditions. The throttle valve is then slightly closed, and the load is adjusted to maintain the same speed for further measurements. This process is repeated until the minimum throttle opening at which the engine can operate stably is reached, obtaining fuel consumption data at different loads and speeds. The trend of engine load characteristic curves at different speeds is similar, with only specific numerical values differing.
Having driven for over a decade, I believe normal engine load values depend on road conditions and driving habits. During smooth city driving, the load typically ranges between 20%-40%, with stable RPM and reasonable fuel consumption. When climbing steep hills or accelerating sharply, it's common to see a momentary spike to 70%, but it quickly drops back. What worries me most is prolonged high load situations, like towing a caravan uphill with sustained loads above 80%, which can easily lead to overheating and carbon buildup. Once my OBD scanner showed idle load exceeding 25%, which turned out to be due to a dirty throttle body - after cleaning, it dropped to around 18%. Regular checks of spark plugs and air filters are crucial, as maintaining good airflow is essential for stable engine loads.
After all these years in auto repair, the normal range of engine load depends on the RPM state. During cold start idling, a fluctuation around 20% is normal, but if it exceeds 30%, you should check for severe carbon buildup. The optimal load during steady highway cruising is 25%-35%, where fuel injection is precise and emissions meet standards. Pay special attention to load fluctuations after hard braking—if it drops below 20% too slowly, it might indicate a mixture imbalance due to a failing oxygen sensor. Last month, I fixed a car that kept complaining about lack of power—it turned out long-term high loads of 50% had damaged the catalytic converter.
