What is the normal working temperature of automobile engine? What does it matter if it is too high or too low?

The normal working temperature of automobile engines is generally between 80℃ and 90℃, and the working temperature of some highly intensified engines can reach above 90℃ 100℃ ... For example, the normal working temperature of gasoline engines for cars is generally between 95 C and105 C, and the normal working temperature of highly intensified diesel engines for trucks is generally between 85°C and 95 C (. When the engine is running at this temperature, the fit clearance of each part is just within the design range, the combustion state of fuel in the combustion chamber is the best, and the thermal efficiency and all aspects of the engine are in the best state. If it is lower than this temperature, we call it engine supercooling; Above this temperature, we call it engine overheating. Whether it is too cold or too hot, it has a great influence on the service life of the engine.

First, let's look at the influence of engine supercooling. After the car is parked for a period of time, the temperature of the engine will naturally cool to the ambient temperature, which is quite different from the normal working temperature, especially in winter in the north, and the ambient temperature is even as low as -30℃, which is very harmful to the engine.

Generally, we call the period when the engine starts to the normal working temperature as the cold start stage of the engine. Experimental data show that the wear of automobile engine reaches 80%.

But at the moment of cold start, the wear of the engine at low temperature is 6 times that at normal working temperature! When the engine temperature is 40~50℃, the engine wear increases by 60%~80%, the power decreases by 25%, and the fuel consumption increases by 8%~ 10%. This is also one of the important reasons for the high fuel consumption and short engine life of vehicles used in Northeast China.

In addition, engine supercooling has more hazards:

1. The temperature of mixed gas (or air) entering the cylinder is too low, and the quality of combustible mixed gas is poor, which makes ignition difficult or combustion slow, leading to the decrease of engine power, the increase of fuel consumption and the emission of harmful gases.

2. The viscosity of lubricating oil increases, which leads to poor lubrication, aggravated parts wear and increased engine power consumption;

3. The water vapor in the combustion products is easy to condense into water, which forms acid with acid gas, which intensifies the erosion of the machine body and parts;

4. Oil film on the friction surface (cylinder wall, piston, piston ring, etc.). ) was washed by the fuel that was not vaporized because of the low temperature, and the lubricating oil was diluted, which aggravated the wear of parts.

Therefore, maintaining the normal working temperature of the engine is an important condition to ensure the good work of the engine, improve the working reliability and prolong the service life. At present, many measures have been taken to make the engine warm up quickly, such as installing thermostat, using fan clutch or electronic fan, using shutters with automatic opening adjustment and built-in exhaust pipe. We should ensure that these devices are in good condition when using the car, especially it is not allowed to remove the thermostat to prevent the engine from being hot.

Let's look at the effect of engine overheating. Under normal circumstances, when the engine temperature is higher than the normal temperature range, the coolant boils and vaporizes, and thick white fog emerges from the water tank cover. This phenomenon is called engine high temperature. The causes of high engine temperature include damaged water pump, insufficient or unqualified coolant, damaged thermostat, non-rotating fan, dirty water tank surface, and poor heat dissipation. The harm of engine high temperature is also great.

1. When the engine temperature is too high, the air temperature entering the engine is also relatively high, so the actual amount of air entering the engine is less, which reduces the charging efficiency of the engine, and the power and torque of the engine are also reduced, indicating that the engine power is insufficient;

2. When the engine temperature is too high, the temperature in the combustion chamber is very high, which is easy to reach the ignition point of gasoline, ignite the mixed gas, cause deflagration, cause strong impact and vibration of the engine, and cause early damage of parts due to additional impact load;

3. When the engine temperature is too high, the piston will expand excessively, which will reduce or even disappear the fit gap between the piston and the cylinder wall, thus increasing the movement resistance of the piston and even pulling the piston and the cylinder wall. The normal clearance of other moving parts is also destroyed, resulting in increased wear and even damage;

4. When the engine temperature is too high, the viscosity of lubricating oil will decrease, and a good oil film cannot be formed on the friction surface, which will worsen the lubrication condition and aggravate the wear of parts;

5. When the engine temperature is too high, the elasticity of the piston ring will drop sharply, and the gap between the piston and the cylinder wall can't be sealed well, and the functions of oil scraping and oil distribution can't be better completed, which leads to engine exhaust, engine oil burning and other failures. And this damage is irreversible. Practice has proved that if the engine experiences two high temperatures, the elasticity of the piston ring basically disappears, and the engine will soon have the fault of burning oil. Only the engine can be overhauled at this time. The mechanical strength of other parts will also be reduced, and even the friction pair will be deformed and destroyed.

Therefore, whether the engine temperature is too high or too low, it is very harmful to the engine and will greatly shorten the service life of the engine. We must keep the engine cooling system in good condition during use, and do not disassemble or adjust the cooling intensity adjusting device easily to ensure the normal working temperature of the engine.