What is the normal RPM range for a truck?
2 Answers
The normal RPM range for a truck is generally between 500~800 r/min. If the RPM is too low, the engine may vibrate; if it's too high, it will lead to increased fuel consumption. As long as there is no vibration, design engineers aim to keep the RPM as low as possible to save fuel. Additional information: 1. During idle, the cylinder leakage is higher, leading to more energy loss in the cylinders, resulting in lower compression temperature and pressure, poor fuel atomization, and greater combustion fluctuations. The fuel supply during idle is small, and minor variations in fuel supply to each cylinder can cause differences in their working conditions. This uneven fuel supply during idle can lead to the 'idle hunting' phenomenon in diesel engines. 2. The direct injection in diesel engines has led to the development of high-pressure fuel injection, especially with the use of multi-hole injectors. This makes the injector less precise when supplying small amounts of fuel, leading to fluctuations. Unstable fuel supply in diesel engines is a major cause of idle instability. 3. As the fuel injection system ages with prolonged use, differences in components like injectors and delivery valves among cylinders can lead to further uneven fuel distribution, exacerbating idle RPM fluctuations.
I've been driving trucks for over a decade, and I find the most comfortable idle speed to be between 700 and 900 RPM, as long as the engine runs smoothly without any shaking. When driving on highways, maintaining the RPM between 2000 and 2500 is ideal, as this range offers the best fuel efficiency with sufficient power. Different brands may vary; for example, my Foton truck idles at 750 RPM, while a FAW truck might idle as high as 850 RPM. When carrying heavy loads or going uphill, the RPM naturally increases to around 3000, but prolonged high RPM should be avoided to prevent accelerated engine wear. It's normal for the RPM to be higher during cold starts in winter, but it should drop back after about a minute. The key is to adjust your driving rhythm based on the dashboard signals, avoiding aggressive acceleration to save fuel and ensure safety.
