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What is the engine/what does it do?

It goes without saying that the heart of a vehicle is the engine. Without it your vehicle will be going nowhere fast, so it’s important to keep it running smoothly and recognise any signs of engine trouble before they become catastrophic. There are two main types of engine, the diesel engine and the petrol, and both of these engine types use internal combustion (small explosions) to operate the engine.

Getting into the details of the engine

The engine has a series of pistons attached to a crankshaft below them and a camshaft above them via a connecting rod. The amount of pistons varies depending on the vehicle. Motorcycles for example, often have two cylinders, but a vehicle can have up to eight depending on the power of the engine. These cylinders can be positioned in an inline position, sideways, as in a VW Beetle (known as a flat four), or in a V position such as a V6 or V8 engine.

The job of the crankshaft is to carry power generated by the pistons to the rest of the vehicle, and eventually the wheels in order to move the vehicle. This crankshaft has counterweights to ensure that its movement is consistent. The crankshaft is attached at the side to the engine’s flywheel. The flywheel stores torque from the torque converter, and combined allows the engine to spin independently of the transmission.

The crankshaft, along with the camshaft are controlled by a timing belt to ensure that they both move in synchronicity. This is important as the correctly timed opening and closing movement of the engine’s valves are essential to prevent the pistons from striking the valves when moving.

When an engine is operating, it goes through what is commonly known as ‘four strokes.’ The first is intake stroke, which is where the piston is in the top position and moves down, allowing the engine to take in petrol and air.

The next is the compression stroke, which is where the valves close and the piston moves back up compressing the fuel and air mixture.

The third stroke differs between a diesel and petrol engine, but nonetheless is still called the power stroke. In a petrol vehicle a spark is given off by a spark plug which ignites the fuel and water mixture. In a diesel engine, the fuel is injected in to the compressed air. Because compressed air is hotter than non-compressed air the introduction of the diesel causes combustion when the two mix. In either case, the fuel mixture explodes, and drives the piston back in to the down position.

When the piston hits the bottom this opens the exhaust valve and the remaining spent fuel mixture leaves the exhaust.

What if something goes wrong with the engine?

There are many reasons in which a vehicle’s engine can fail and these are most often caused by damaged or worn engine parts. For example, a lack of compression in your engine could be caused by a problem with the cylinder, or damage to the piston or its surrounding ring. This could cause air to be leaked out of the engine.

Alternatively, a spark plug can fail. Firstly, try cleaning off a spark plug as this can sometimes sort the problem. If a spark plug has failed, it will need to be replaced as this provides the essential spark to the engine’s internal combustion. A lack of power could also be caused by the ignition timing being wrong, which will cause the spark at the wrong time. Alternatively, the battery could be flat, meaning the engine can’t be turned over.