Driver Guide To A Car Engine Operation
31st January 2011
Driver Guide To A Car Engine Operation
Your engine is one of the most complex assemblies under the hood (second only to the transmission). It is filled with moving parts that work together seamlessly to propel your vehicle down the road. But few people are familiar with the process that makes this possible.
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Below, we’ll take you on a brief tour of your car’s engine. You’ll learn about the components that play key roles in its operation. We’ll describe what these parts do so you’ll understand how they contribute to the performance of the assembly. You’ll also begin to appreciate why certain problems surface as the components wear down over time.
Major Components Of Your Engine
The size and power of the assembly is dictated by the number of pistons. Small passenger vehicles may only have four. Sedans may have six, and larger automobiles and performance vehicles often have eight. Some trucks come with more. Each piston is contained within a cylinder. The top section of the cylinder is called the combustion chamber. The piston rises up and down according to a precisely-timed 4-stroke combustion cycle (described in more detail in the following section).
Each of the engine’s pistons are attached to a shared component called the crankshaft. As the pistons rise and fall within their respective cylinders, the crankshaft turns on its axis. It rotation moves your vehicle.
Atop each cylinder is found an intake valve and an exhaust. These open and close to help regulate the flow of fuel, air, and exhaust. The valves are connected to camshafts, which, in turn, are connected to rocker arms, lifters, and other parts. These comprise your car’s valvetrain.
Together, the pistons, crankshaft, and valvetrain control the timing of your engine’s 4-stroke combustion cycle. This cycle occurs inside each cylinder, and is the most important task for which your engine was designed.
The 4-Stroke Combustion Cycle
Recall that fuel enters the cylinders through the intake valves. Also, recall that the up-and-down movement of the pistons causes the crankshaft to rotate, which moves your car. What follows is a step-by-step description of this process. There are four distinct strokes: intake, compression, power, and exhaust.
The intake stroke occurs when a camshaft forces the intake valve open. As it opens, the piston descends within the cylinder. Air and fuel fill the chamber, after which the intake valve closes.
The compression stroke begins when the piston starts to rise from the bottom of the cylinder. With the intake valve sealed, the air-fuel mixture in the combustion chamber starts to compress. By the time the piston reaches the top of its path, the mixture will have been compressed to approximately 10 percent of its beginning volume.
During the power stroke, a spark plug at the top of the cylinder ignites the compressed air-fuel mixture. This produces a rapid expansion of gases. The vapors push the piston downward in the cylinder, causing the crankshaft to rotate.
The exhaust stroke is the last stroke in the cycle. At this point, the piston is at the bottom of the cylinder. The exhaust valve opens, and the piston begins its ascent again. This pushes the vapors in the combustion chamber out of the cylinder via the open valve. Once the gases have been expelled from the chamber, the exhaust valve closes, and the combustion cycle begins anew.
How To Extend Your Engine’s Life
The components mentioned thus far (pistons, valves, camshafts, crankshaft, etc.) will eventually wear out. Under normal driving conditions, a new engine can be expected to last 100,000 miles or more before it needs to be overhauled or replaced. You can prolong its life by keeping the oil level replenished, and changing the oil according to the service interval recommended by your owner’s manual.
Also, make sure to have the timing belt replaced every 60,000 miles. If it breaks while your engine is in operation, it can cause expensive damage to the valves and pistons.
Being familiar with your engine and how it operates is useful for troubleshooting sporadic issues. While repairing engine problems may be beyond your skill and experience, knowing what caused the problems in the first place can prove invaluable.
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