I’ll show you how the four-stroke engine works here in a bit, but before I do, I thought it would be helpful to go through the various parts of an engine so you’ll have an idea of what’s doing what in the four-stroke process. There is terminology throughout these explanations that relies on other terms in the list, so don’t worry if you get confused at first. Read through the whole thing to get an overall grasp, and then read it again so you have a basic understanding of each piece as it’s being talked about.
Engine Block (Cylinder Block)
The engine block is the foundation of an engine. Most engine blocks are cast from an aluminum alloy, but iron is still used by some manufacturers. The engine block is also referred to as the cylinder block because of the big hole or tubes called cylinders that are cast into the integrated structure. The cylinder is where the engine’s pistons slide up and down. The more cylinders an engine has the more powerful it is. In addition to the cylinders, other ducts and passageways are built into the block that allow for oil and coolant to flow to different parts of the engine.
Why is an engine called a “V6” or “V8”?
Great question! It has to do with the shape and number of cylinders an engine has. In four-cylinder engines, the cylinders are typically mounted in a straight line above the crankshaft. This engine layout is called an inline engine.
Another four-cylinder layout is called the “flat four.” Here the cylinders are laid horizontally in two banks, with the crankshaft going down the middle.
When an engine has more than four cylinders, they are divided into two cylinder banks — three cylinders (or more) per side. The division of cylinders into two banks makes the engine look like a “V.” A V-shaped engine with six cylinders = V6 engine. A V-shaped engine with eight cylinders = V8 — four in each cylinder bank.
The combustion chamber in an engine is where the magic happens. It’s where fuel, air, pressure, and electricity come together to create the small explosion that moves the car’s pistons up and down, thus creating the power to move the vehicle. The combustion chamber is made up of the cylinder, piston, and cylinder head. The cylinder acts as the wall of the combustion chamber, the top of the piston acts as the floor of the combustion chamber, and the cylinder head serves as the ceiling of the combustion chamber.
The cylinder head is a piece of metal that sits over the engine’s cylinders. There are small, rounded indentations cast into the cylinder head in order to create room at the top of the chamber for combustion. A head gasket seals the joint between the cylinder head and cylinder block. Intake and outtake valves, spark plugs, and fuel injectors (these parts are explained later) are also mounted to the cylinder head.
Pistons move up and down the cylinder. They look like upside down soup cans. When fuel ignites in the combustion chamber, the force pushes the piston downward, which in turn moves the crankshaft (see below). The piston attaches to the crankshaft via a connecting rod, aka the con rod. It connects to the connecting rod via a piston pin, and the connecting rod connects to the crankshaft via a connecting rod bearing.