What is the reason why there is black ash in the exhaust pipe by hand?

There is black ash in the automobile exhaust pipe, which belongs to carbon deposition. The reason is that the exhaust pipe of a car burning engine oil must be black, but a car with a black exhaust pipe does not necessarily burn engine oil. The black carbon of automobile exhaust pipe is serious. Although it is not a fault, one thing is certain, the air-fuel ratio of the engine is likely to often go wrong, that is, the gasoline in the engine often burns insufficiently, resulting in excessive carbon deposition.

In addition, some unburned oil and gas will be carbonized when catalyzed by three-way catalyst. After a long time, these soot will accumulate in the exhaust pipe, causing the exhaust pipe of more than 80% turbocharged engines to turn black.

Extended data:

Compared with ordinary turbine models, the exhaust pipe of direct injection turbocharged engine is darker, so it can be said that most of them can't escape the fate of black exhaust pipe, even the new exhaust pipe of new car will soon turn black.

The direct injection engine injects gasoline directly into the cylinder through the fuel nozzle, instead of supplying oil through steam. After the direct injection technology is adopted, the fuel enters the cylinder in the form of fine droplets.

Due to the special structure of direct injection engine, its "self-cleaning" ability to carbon deposit on the back of intake valve is much weaker than that of ordinary EFI engine. Therefore, although the direct injection engine has obvious fuel-saving advantages, carbon deposition is also a thorny problem that has to be faced, especially on the back of the intake valve.