The crankshaft is mounted at the base of the engine and is a long steel shaft freely rotating around the attachment points. anchor points (usually four to seven) and crankshaft bearings are called main bearings. A running engine causes the crankshaft to rotate, which is transmitted through the transmission to the wheels of the car.
Connecting rods attached to the crankshaft extend to the pistons inside the cylinders. When the air-fuel mixture inside a well-sealed cylinder is ignited, the explosion forcefully pushes the piston and connecting rod down, and this movement turns the crankshaft. As soon as the piston finishes its active stroke, its subsequent upward movement forces the spent pistons to be discharged out of the cylinder through the just opened exhaust valve. At the top, the exhaust valve closes and the intake valve opens, allowing fresh air/fuel mixture to be drawn into the cylinder by the downward movement of the piston. The intake valve closes, the piston starts moving up again, compressing the mixture in the closed cylinder. Around the top of this stroke, the candle 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 pushing moments on the crankshaft. While the mixture explodes in one cylinder, in the other the piston is already going down, in the third the intake valve opens and in the fourth the mixture is compressed before ignition. Thus, pushing impulses without jerks rotate the crankshaft and a large round flywheel attached to its end, 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 means of a cam (also called distribution) shaft. Candles are screwed into the cylinder heads in such a way that their tips are in the combustion chambers. Because exceptionally accurate valve timing is required (opening and closing) in relation to the process of combustion of the mixture, the camshaft is driven by a belt or chain drive. Each valve is driven by either a push rod (called an overhead valve - a valve above the cam) or a cam pressing on the valve (overhead cam / overhead cam). On all ACCORD and pReLUDE vehicles, engines use the design "upper cam" (OverHead Cam or ONS motors). Some engines use two cams and the engines are called DOHC (Dual Overhead Cam).
Lubricating oil is located in the oil sump at the base of the engine. Lubrication to all parts of the engine is supplied under pressure by an oil pump, which is driven by a crank or camshaft. Oil lubricates the entire engine, circulating in the block and cylinder heads, and, along the way, performs the function of engine cooling by 25-40%.
Due to the fact that the car has to work in a variety of operating conditions, a rotating engine needs a large number of support systems, such as fuel delivery, exhaust regulation, lubrication, cooling, starting, etc. The principles of mechanics, gas dynamics, electronics, etc. are used in the operation of these systems. To learn how to recognize a failed system, it is necessary to acquire knowledge about the signs and causes of possible damage.