Why do automobile exhaust pipes emit white smoke in winter?

That's because once the ambient temperature is relatively low, especially in winter, the exhaust pipe of the car will drip outwards, which is actually a very normal phenomenon. Because gasoline will produce water and carbon dioxide after complete combustion, water is steam at high temperature, and steam is colorless and transparent at high temperature, but when the temperature is lower than 100℃, steam will condense into water. If the condensed water droplets are small and suspended in the air, water vapor will appear in the form of white gas. When the ambient temperature is low, the white smoke emitted from the exhaust pipe is water vapor.

If condensed water drops accumulate, they become water. The water droplets discharged from the exhaust pipe are the result of condensation of water vapor generated after gasoline combustion in the exhaust pipe and muffler. However, when the ambient temperature is high, the water vapor has been discharged without condensation. When the ambient temperature is low, the water vapor will condense on the exhaust pipe wall and flow out with the exhaust gas. This phenomenon is common in cars with good engine working conditions.

Extended data:

Causes of cold start of cars:

1, high viscosity engine oil 10W or 5W is suitable for winter;

2. Too much carbon is deposited in the intake system and intake valve roots, which leads to too thin mixture concentration during cold start;

3. The throttle valve is seriously dirty and the air intake is insufficient;

4, the speed of the starter can not meet the requirements;

5. The contact resistance of the battery connecting wire is too large; The battery power is insufficient;

6. The viscosity of transmission lubricating oil is too thick, resulting in too great engine running resistance;

7. Insufficient compression pressure of engine cylinder;

8. High-voltage ignition system-the performance of spark plug is poor, and it can't produce enough ideal spark to break through the mixture;

9. The spark plug is unreasonable; Engine coolant temperature sensor fault.