Gasoline and diesel engines – what are the differences?

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difference between gasoline and diesel engines

We all need our vehicles to move from A to B, but how this transition is made depends on what type of engine the vehicle has. There are two main types of engine used today – gasoline and diesel engines, but what are the differences between them?

An engine’s purpose is to convert chemical energy, in the form of fuel, into mechanical energy. Without this energy, the vehicle has no means of motion. The conversion of chemical energy into mechanical energy is the primary function of the engine.

Gasoline engines

Gasoline engines work to ignite the fuel, so that its energy can be extracted. This is achieved by the following four steps:

  • Intake stroke – fuel is first combined with air
  • Compression stroke – the fuel-air mixture is compressed by the piston
  • Ignition stroke – the fuel-air mixture is then ignited by a device called a spark plug
  • Exhaust stroke – the piston moves up, expelling exhaust fumes through a valve

Oxygen from the air assists in the ‘ignition’ (or ‘explosion’) of fuel, an ignition caused by the spark plug. The movement of the piston helps to both compress the fuel-air mixture and is also involved in removing excess fumes, caused by the ignition, from the engine.

Diesel engines

In contrast, diesel engines do not have a sparkplug. This means that diesel engines need to ‘ignite’ the fuel by different means. The steps involved in this ignition include:

  • Intake stroke – Air first moves through an intake valve into the engine
  • Compression stroke – Air is compressed as the piston rises
  • Ignition stroke – Fuel then enters the engine, ignition occurs and the piston moves down
  • Exhaust stroke – Piston moves up and exhaust fumes escape through the exhaust valve

Yes – the steps are similar, but there are notable differences. Note how, with a diesel engine, the pressure needed to compress air is much, much higher. Without a spark plug, this higher pressure is needed to eventually ignite the air-fuel mixture.

If gasoline engines used the same degree of pressure, it would result in auto-ignition; part of the reason why gasoline engines use considerably lower pressures. These differences in ignition have notable effects on fuel efficiency.

For example, higher compression rates (with diesel engines) results in greater fuel efficiency (36 percent higher). It maximizes the amount of energy one extracts from fuel, in a way that gasoline engines fail to deliver. Diesel engines have become popular for precisely this reason. Diesel fuel is also less volatile, and its vapor less explosive, when compared to gasoline.

If you can think of any more facts about gasoline and diesel engines, be sure to comment below. Check back to our Vegas Cash for Cars blog for even more interesting facts about cars.

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