When combustion gases escape through the exhaust valves they help to create a “scavenging” effect that helps to pull the intake air in. The intake valves open slightly before the piston reaches the top end of the exhaust stroke. Similarly, the exhaust valves open before the piston reaches the bottom of the power stroke, as the majority of the useful work has already been done by the gases and the pressure surplus in the cylinder should be minimized so that the exhaust stroke doesn’t have to actively compress the exhaust gases. If you look at the cross section of the block you’ll notice that the areas around cylinders are empty:įirstly, notice that the intake valves close after the piston reaches the bottom end of the intake stroke – the air coming through the valve has some inertia, which, especially at high engine speeds, makes it pile up in the cylinder despite the opposite movement of the piston. You may also have realized that the top part of the block is perfectly flat – we’ll soon attach another component there. The sides of the block are reinforced by various ribs to improve the rigidity of the structure – the body has to withhold the power of the explosions inside the cylinders. Other engines may use different arrangements of cylinders, usually in a flat or V-shape configuration. Since the four cylinders are inline, the engine we’ll build is known as an inline four cylinder engine. I’ll discuss these concepts in more depth near the end of the article.

in a lawn mower, a typical car engine has more than one cylinder to ensure a more even delivery of power.

While it’s often acceptable for smaller engines e.g. This uneven action creates a lot of vibration. Recall that a piston exerts a pushing force on the crankshaft only during the power stroke, so only for about a quarter of time. Notice that this block contains four large cylindrical openings that define the four cylinders.

Car engine builder 3d