Why are all the car companies stopping their diesel engines in India?

To know the answer to this we have to first understand the main difference between a diesel and a petrol engine.

Petrol has short chain hydrocarbons and hence is easy to ignite. While diesel contains long chain hydrocarbons which requires a very high temperature to combust. They also produce a lot of smoke and hence greater residual exaust gases.

Petrol engines use spark plugs and easy to make and hence cheap. While diesel engines use fuel injection and the fuel is ignited by compression of air-fuel mixture. Diesel engines are hence expensive to build.

In the past vehicle emission regulations (Bharat standard) were not so strict. Hence running a diesel vehicle was significantly profitable to run in the long term than a petrol vehicle. But in the past few years due to more strict regulations like the BS5 and the BS6 it became mandatory for all vehicles to conform to these standards. Which meant that the fuel economy provided by these diesel engines will be reduced. This is because to reduce the emissions the combustion temperature has to be reduced, which inturn decreases the fuel economy.

Hence, the difference of fuel economies between petrol and diesel engines reduced. Diesel engines no longer had the advantages it used to have over petrol engines.

Hence major companies like Suzuki and Hyundai stopped producing diesel cars.

But diesel engines are still used in more heavy- duty vehicles like SUVs and Cross-overs.

Why are diesel locomotives so noisy compared to electric locomotives?

The only sound Electric Locomotives produce are of the cooling blowers that blow air to cool the internals of the Locomotive.

Diesel Locomotives unlike electric Locomotives don't need OHE for power because they contain their own power source i.e. the prime mover.

Prime movers are essentially very big diesel internal combustion engines. Consider a normal diesel engine but with very big displacement e.g. 126000 cc and in a V12 or V16 configuration or V8 for shunters like WDS 6(I don't remember)

Above, ALCo 251 V12 diesel engine used in India locos of ALCo origin.

Diesel Locomotives as the name suggests, run on Diesel burning prime movers and like every other internal combustion engine, produce energy in the forms of mechanical, heat and sound energy.

The mechanical energy is used to run an alternator that produces electricity for the traction motors that turn the wheels of the Locomotive.

Above, an Locomotives alternator.

The heat energy is dessipated through the radiator into the atmosphere

The sound that is produced from the combustion is what we here. These sounds are produced due to small scale detonation of diesel under pressure that happens with each combustion cycle. Modern diesel engines come in either 2 or 4 stroke cycles, that means a cycle of combustion is completed when the Piston completes 2 or 4 strokes.

In consumer vehicles, the sound is expelled through the exhaust manifold that leads to the muffler. The muffler contains catalytic converter that reduces the amount of harmful pollutants released into the atmosphere and as the name suggests, it “muffles” or reduces the sound of the engine.


Above, an exhaust muffler.

Diesel Locomotive have straight pipe exhausts that almost don't have any kind of muffling capabilities so therefore diesel Locomotives produce sounds. But this sound is what adds to the charm of the diesel Locomotives. An accelerating ALCo Locomotive is one of the best sounding machines.