Updated: Sep 9, 2021
Engines - An engine or a motor is a machine designed to convert one or more forms of energy into mechanical energy.
An internal combustion engine (ICE) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some components of the engine. The force is applied typically to pistons, turbines, blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into useful kinetic energy and is used to propel, move or power whatever the engine is attached to. This replaced the external combustion engine for applications where the weight or size of the engine is important. There are two main types of fuels used widely in internal combustion engines, that is petrol and diesel.
Petrol Engines :
Petrol Engines are smoother and produce less knocking than diesel engines. These engines use a spark plug to help and cause the ignition in the engine block which is why combustion is complete. The calorific value is 45.8 MJ/kg, which is slightly more than diesel. These engines have lower compression ratios than diesel as they have spark plugs for the ignition and the engines are therefore less bulky. Petrol engines are all about revolutions per minute (rpm), and they tend to achieve peak power at higher rpm. Petrol vehicles are slightly cheaper to buy and service.
Diesel Engines :
They are comparatively less smooth and produce knocking when RPMs go low. They use compression as the method to combust the fuel. Diesel doesn't need an external spark plug as it can ignite on high compression. That is why the engine block is thicker and heavier to be able to handle the forces of the high compression. Diesel Engines also produce more torque than petrol but need more maintenance as lots of soot can be collected from the headers and exhausts. Since Diesel is denser than Petrol, it produces more energy when combusted and gives higher efficiency. Due to these improvements, they are also costlier than petrol.
In the modern-day context, diesel and petrol engines are usually compared by way of their impact on the environment (emissions and noise). Even though electric powertrains are coming up, there is still time for it to be mainstream, and a few more years to reduce the usage of petrol and diesel.