The crankshaft is attached to the base of the engine and is a long, steel shaft that rotates freely around mounting points. The mounting points (usually four to seven) and the crankshaft bearings are called main bearings. When the engine is running, the crankshaft rotates, which is transmitted to the vehicle's wheels via the transmission.
Attached to the crankshaft, the connecting rods extend to the pistons inside the cylinders. When the fuel-air mixture ignites inside the tightly sealed cylinder, the explosion pushes the piston and connecting rod downward with force, and this movement turns the crankshaft. As the piston completes its active stroke, its subsequent upward movement forces the spent gases to be expelled from the cylinder through the exhaust valve, which has just opened. At the top, the exhaust valve closes and the intake valve opens, allowing fresh fuel-air mixture to be sucked into the cylinder by the downward movement of the piston. The intake valve closes, and the piston begins its upward movement again, compressing the mixture in the closed cylinder. Around the top of this stroke, the spark plug ignites, the mixture explodes, and a new stroke begins. If you count the number of piston movements in a cycle, you will understand why automobile engines are called four-stroke.
At the same time, all cylinders are in different stages of the cycle. This is necessary to ensure uniformity of the flow of pushing moments to the crankshaft. While the mixture explodes in one cylinder, the piston in another is already moving down, in the third the intake valve opens and in the fourth the mixture is compressed before ignition. Thus, the pushing impulses rotate the crankshaft and the large round flywheel attached to its end without jerks, providing with its mass sufficient rotational inertia to maintain the stability of the cycles in the cylinders.
At the top of the engine, the cylinder heads provide a good seal for the combustion chambers. Each combustion chamber contains at least one intake and one exhaust valve, which are opened and closed by a camshaft (also called a camshaft). The spark plugs are screwed into the cylinder heads so that their tips are in the combustion chambers. Since extremely precise timing of the valve action (opening and closing) in relation to the combustion process of the mixture is necessary, the camshaft is driven by a belt or chain drive. Each valve is driven either by a push rod (called an overhead valve - valve over cam) or by a cam pressing on the valve (overhead cam). All ACCORD and pReLUDE cars use an "overhead cam" design in their engines (OverHead Cam or OHC engines). Some engines use two cams and are called DOHC (Dual Overhead Cam) engines.
Lubricating oil is located in the oil pan at the base of the engine. Lubrication is supplied to all parts of the engine under pressure by an oil pump, which is driven by a crank or camshaft. The oil lubricates the entire engine, circulating in the block and cylinder heads, and, incidentally, performs 25-40% of the engine cooling function.
Due to the fact that the car has to work in a variety of operating modes, the engine rotating the shaft requires a large number of support systems, such as fuel delivery, exhaust regulation, lubrication, cooling, starting, etc. The operation of these systems uses the principles of mechanics, gas dynamics, electronics, etc. In order to learn how to recognize a failed system, it is necessary to acquire knowledge about the signs and causes of possible damage.
[Original material on the website: HONDABOOK]