4 stroke engines are considered ideal for so many reasons. This hasn’t always been the case though. Not so long ago, all car lovers had were 2 stroke engines. But like it is often the case in the automotive field, things change so fast. 4 stroke engines came into the market and everyone liked them. Volvo, being the automotive giant it is, sought to not just embrace the 4 stroke engine concept but to also improve it. They lived up to their expectations as one of the most innovative brands in the world. The engine model is available in nearly all new Volvo models. But how does it work in the first place? Is there anything that makes it better or special compared to 2 stroke engines? Read on to learn more.
As the name suggests, Volvo 4 stroke engines have four separate strokes. There is the intake, the compression, combustion and finally, exhaustion. That explains why they are stronger than 2 stroke engines. Note that each of these strokes has a special function.
It is a piston stroke also known as suction or induction. The stroke begins at the Top Dead Center (TDC) and concludes at the Bottom Dead Center (BDC). For the intake stroke to work, the intake valve should be in the open position. This makes it easy for the piston to pull an air fuel mixture into the cylinder by generating vacuum pressure inside the cylinder via its downward motion. As the piston moves down, air gets sucked in through the downward motion against the piston.
Unlike intake stroke, compression begins at the BDC or at the end of the intake stroke. The piston here compresses air-fuel mixture as it prepares for ignition which happens during the power stroke. Note that both the exhaust and intake valves are closed as this happens.
Also referred to as ignition or power stroke, it is the stroke that happens at the start of the second revolution of the four stroke cycle. It is perhaps the most important cycle because at this exact point, the crankshaft swiftly completes a complete 360⁰ revolution. While the piston is at the end of the compression stroke (TDC), the compressed air fuel mixture gets ignited by the spark plug. This forces the piston to return to BDC. That explains why the combustion stroke produces mechanical work from the car engine so as to turn the crankshaft.
The Exhaust Stroke
It is sometimes referred to as the outlet stroke. Here, the piston returns from BDC to TDC again. The exhaust valve is also open at this time so as to allow expulsion of spent air and fuel mixture through the rear exhaust valve.
Petrol and Diesel 4 Stroke Engines
The main difference between 4 stroke diesel and 4 stroke petrol Volvo engines boils down to how these two models burn air fuel mixture. In petrol engines, the burning of air fuel mixture is ignited by the spark plug. This is a little bit different in diesel engines where burning or air fuel mixture occurs as a result of highly compressed hot air. There’s also spark plug in diesel 4 stroke engines.