Engine Operations
This is another of the questions that could easily yield a book as an answer but I will limit it to fairly non-technical descriptions. We rely on the vehicles we drive every day to get us to and from the places we need to be. Although your vehicle is "an old fried" to you and you are familiar with the idiosyncrasies it has, do you really know what actually happens when you turn the key and start the engine? There are numerous things that must happen in the proper order and at the proper time just to start the engine; many more have to happen to get the vehicle to move in a useful and safe manner. Hopefully, this will answer your questions of "How does my engine really work"? For the purposes of this explanation, we are assuming that this is a gasoline powered engine. During the process of answering this broad question, I do suggest that you follow the links to other pages that I have written. They will assist in the overall understanding.
Put the key in the ignition switch and turn it to the point that the starter engages. The starter is an electrical motor that has small teeth on it, gears if you will, that mesh with the teeth on the engine's flywheel. Once the key is released to the normal position, the starter is disengaged and is no longer involved in the operation of the engine. The flywheel stands in a vertical position at one end of the block, usually the back, and is bolted to the end of the engine's crankshaft. Obviously, being bolted to the crankshaft, it turns at the same speed that the crankshaft turns. There are also other engine components that are connected to the crankshaft; all are important and each will be discussed. In each engine, there are cylinders in the block. The most popular quantities are 4, 6 and 8 for automobiles and light trucks. There are automotive engines with more and probably some with less. Inside each cylinder is a piston with a set of rings on it. That piston is attached at one end to a connecting rod, which is attached to the crankshaft. The end that attaches to the crankshaft rises and lowers as the crankshaft turns and spins freely because of rod bearings where it is attached.
In each cylinder, in union with the cylinder head, there are valves that allow fuel to enter and burned gases to exit. (See my pages on Diesel and Gasoline Engines, Fuel System Information and Engine Internal Lubrication for some preliminary information.) How those valves open and close is controlled by the timing pattern of the camshaft lobes, timing chain and gear, push rods, lifters, rocker arms and valve springs all working together. Inside that same area of the cylinder is a spark plug that creates the ignition for the compresses fuel that arrives in the cylinder at the proper time. During the starting process, the crankshaft causes the pistons to move up and down, being the power for the engine until it starts; however, after the engine starts, the pistons cause the crankshaft to turn, which in turn, after turning the transmission, causes the car to have the needed energy to propel itself.
After the engine starts, the continual and controlled explosions in each of the cylinders' combustion chambers, produces the energy to generate the rotary movement of the crankshaft at various and controlled speeds. Electrical power for the vehicle, including the spark, is supplied by the alternator. That electrical voltage is 13.8 volts, as opposed to the 12 volts of the battery. That runs and powers all of the needed 12 volt devices on the vehicle, and in turn charges the battery. The greater power is created as the primary voltage is stepped up, transformed if you will, by the coil. The higher voltage is then sent at the proper time to the spark plugs to create the explosion. Because the constant explosions generate a tremendous amount of heat, the engine must be cooled in some manner. That is done by a series of jackets around the cylinders, carrying a cooling liquid around the cylinders to carry away most of the heat. (See our section on the Cooling System.) Burned gases are carried away by the exhaust system. Assuming that fuel and air is supplied in the proper mixtures, the engine keeps running until you turn it off.
Without going into all of the details, the engine runs faster as you press on the accelerator to add more fuel. The faster the engine turns, the more power the vehicle has. That rotational engine power is then passed on to the transmission, manual or automatic, which in turn sends it to the driveshaft, through a universal joint, to the differential, and ultimately to the drive wheels, which make the car move. The transmission determines if the vehicle moves forward or in reverse. Items such as the alternator, power steering, and air conditioning also get the ability to work from the turning of the engine. They are connected directly to the engine by way of pulleys and fan belts, as is the water pump that pushes the flowing liquid that cools the engine. Each of these connections takes away some of the engine's power but supplies some other form of useful addition.
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