Question

The colour of exhaust from diesel engine is generally __________

(a) white

(b) bluish

(c) black

(d) violet

I had been asked this question by my college director while I was bunking the class.

The question is from Comparison of Two Stroke S.I. and C.I. Engines topic in section Two Stroke Engines of IC Engine

Answer 1

The correct answer is:

(c) black

Explanation:

In a diesel engine, the exhaust gas typically appears black. This is often due to incomplete combustion of the fuel, leading to the presence of soot particles or unburned fuel in the exhaust gases. 

Here’s a breakdown of common exhaust colors:

- **White exhaust**: Typically seen in cold weather or when the engine is initially started, it may indicate water vapor or coolant in the combustion chamber, such as in cases of engine coolant leaks.

  

- Bluish exhaust: Indicates burning oil, which may be caused by engine wear or a faulty valve seal.

- Black exhaust: Common in diesel engines, it indicates excess fuel is being burned, often due to improper fuel-air mixture, faulty injectors, or incorrect tuning.

Thus, black exhaust is the typical color for a diesel engine.