If you drive a car, you surely know what type of engine the car has, but have you ever wondered why there are types in the first place? Both of these engines have their advantages and disadvantages, as well as similarities to each other.
One of their similarities is that both engines consist of the four basic strokes, intake, compression, power and exhaust.
Differences in the way the two fuels burn
When gasoline evaporates it gets mixed with air, and once the engine intakes this mixture it takes no more than a spark to ignite it. Diesel, on the other hand, doesn’t mix with air properly, but if it’s sprayed into the heated air, a spontaneous combustion occurs. In other words, the engine intakes only air and inserts fuel into it once it’s compressed so that it can light the fuel.
So, in petrol engines the fuel and the air are pre-mixed, while in diesel engines mixing happens during the combustion. Hence diesel engines use a fuel injector, and petrol engines use a spark plug.
Differences concerning sound
Petrol engines make less noise and also vibrate less in comparison with diesel engines because of the smoothness of the process in pre-mixed fuel and air. Diesel engines can’t be as quiet because the ignition can start anywhere in the combustion chamber, which is an uncontrolled process.
Differences in size
In order to reduce the noise they make and their vibration, the structural design of these engines is more rugged and therefore they are heavier than petrol engines. Petrol engines are preferred because of their lightweight design.
Efficiency and fuel economy differences
It’s well known that higher compression ratio means a more efficient cycle. This is where diesel engines beat gasoline engines, because by compressing only air they can reach a good ratio without the risk of self-ignition. Gasoline engines, which compress a mixture of air and fuel, can’t reach such a high compression ratio because of the higher self-ignition risk. That means that diesel engines also have better fuel economy.
What would happen if you put petrol into a diesel engine or vice versa?
Diesel in a gasoline engine won’t do anything, because it’s less volatile than and won’t mix with the air the way gasoline would, so the sparking won’t ignite it.
Putting gasoline in a diesel engine isn’t recommended either, as it’s very unstable and in combination with the hot air in the chamber, it will cause detonations and damage.