The normal human body temperature is 36.5-37.2°C; temperatures below or above this range indicate an abnormality. An engine, much like the human body, needs a specific temperature range to function optimally. Excessive engine temperature can cause cylinder block or cylinder head deformation, increased clearance in parts leading to coolant or gasoline oil leaks, and in severe cases, cylinder scoring. However, excessively low engine temperature will also result in poor engine performance. For example, in winter mornings, the warm-up time is usually longer to allow the engine to reach a stable operating temperature. If the temperature is low, the engine idle speed will not be ideal. Engine temperature is generally judged using a coolant temperature gauge; a gauge temperature of 80°C-90°C is considered reasonable.
Everything expands and contracts with temperature changes.
Engines operate in harsh environments. Their exteriors are constantly exposed to air, experiencing significant temperature variations depending on time and region. They are also affected by dust, vibration, and electrochemical corrosion. Internally, they operate under high temperature and pressure, and are subject to frequent explosions and friction. Therefore, engines are designed and manufactured using very high-quality materials that are relatively unaffected by temperature changes. Even so, some degree of thermal expansion and contraction still exists. Ideally, the engine temperature should be maintained at 90 degrees Celsius, as indicated by the coolant temperature gauge.
Although the piston rings are tightly attached to the cylinder wall and have a certain tension, there will be a certain gap because they are in moving contact. When the temperature is relatively low, the cylinder wall will contract more than the piston rings. This will inevitably cause the resistance during piston movement to be higher than at normal temperatures. As a result, the idle speed will be lower and more unstable. Moreover, because of the tightness, the engine oil may not be able to lubricate properly, which will lead to much greater wear.
Low temperature affects fuel supply performance
For gasoline to burn completely, two things are necessary: controlling the air-fuel ratio and ensuring that the gasoline is fully atomized in the combustion chamber. This increases the contact area between the fuel and air, making ignition easier and ensuring that the fuel burns completely and promptly. This maximizes the engine's thermal efficiency, reduces emissions, and results in ideal vehicle power.
If the engine temperature is low, the fuel injected into the manifold, after being drawn in by negative pressure, doesn't evaporate as ideally, resulting in incomplete atomization. This requires more ignition energy to ignite, and even then, combustion is often incomplete. In modern fuel-injected vehicles, poor combustion leads to sluggish power. The ECU will then increase the fuel injection, significantly increasing fuel consumption, emissions, and carbon buildup, directly impacting spark plug life. Carbon particles also exacerbate friction between the piston rings and cylinder liners, causing severe wear and potentially damaging the catalytic converter and oxygen sensor.
Furthermore, some of the unburned gasoline will adhere to the cylinder walls, directly reducing the effectiveness of the engine oil. Some may even seep into the crankcase, mixing with the engine oil and decreasing its viscosity, resulting in poor lubrication and ultimately accelerated wear on parts. Even if you can detect the oil deterioration in time and change it, the long-term excessive oil consumption will significantly increase maintenance costs.
Other adverse effects
Low engine temperature means lower cylinder wall temperature, resulting in faster heat dissipation. This leads to lower pressure in the air-fuel mixture within the cylinder, causing incomplete combustion and resulting in unstable engine speed or insufficient torque. Gasoline contains hydrogen, which produces water upon combustion. If the engine is at low temperature and pressure, this water cannot completely evaporate and escape. Water droplets remaining in the cylinder, along with other impurities, can create a galvanic effect on the cylinder's metal components, causing corrosion.
At low temperatures, engine oil viscosity increases, and its flow properties significantly decrease. Similar to winter, a more fluid oil is needed. Due to inadequate lubrication, piston rings, camshafts, and bearings wear much faster than usual. The engine has a cooling system that controls the circulation, a closed-loop control circuit. A thermostat regulates the large and small circulation cycles to ensure the engine temperature remains within a certain range. If the engine temperature is low, it is essential to check the thermostat for proper function.
