Most of the cars we have today have gasoline powered engines. Gasoline engine is an internal-combustion engine which generates power by burning a liquid fuel or gasoline, or a gasoline mixture like ethanol with ignition that is initiated by an electric spark.
Gasoline engine have different types which depend on several criteria. These criteria include their application, method of fuel management, ignition, rotor arrangement, strokes per cycle, cooling system, and valve type and location. Two basic engine types are piston-and-cylinder engines and rotary engines.
- Piston-and-Cylinder Engine: In this type of engine, the pressure produced by combustion of gasoline creates a force on the head of a piston that moves the length of the cylinder in a back-and-forth motion. The force it exerts drives the piston away from the head of the cylinder and performs work.
- Rotary Engine: This type of engine does not have conventional cylinders fitted with back-and-forth moving pistons. The gas pressure acts on the surfaces of a rotor instead, which cause the rotor to turn and thus perform work.
Components of a Gasoline Engine
A gasoline engine is composed of different parts and its overall structure may vary depending on the intended application. Here are the essential components of a piston-and-cylinder engine.
- Cylinder Block
This is the main structural member of all automotive engines. It usually extends upward from the center line of the main support for the crankshaft to the junction with the cylinder head. The block stands as the framework of the engine. It carries the mounting pad by which the engine is supported in the framework. The cylinder block of an automobile engine has appropriate surfaces and threaded holes for attaching the cylinder head, main bearings, oil pan, and other units.
- Combustion Chamber
The size, location, and position of the piston within the cylinder defines the combustion chamber. The combustion chamber is an enclosed space in an internal combustion engine where the fuel mix is burned.
These are cup-shaped cylindrical castings of steel or aluminum alloy. Its upper closed end which is called the crown, forms the lower surface of the combustion chamber. It receives the force applied by the combustion gases. Its outer surface is made to fit the cylinder bore closely and is indented to fit the piston rings that seal the gap between the piston and the cylinder wall. There are plain compression rings in the upper piston grooves which prevent the combustion gases from blowing past the piston. Its lower rings are vented to distribute as well as to limit the amount of lubricant on the cylinder wall.
- Connecting Rod and Crankshaft
The connecting rod is a shaft that connects the piston to the crankshaft. It converts the reciprocating or back-and-forth motion of the piston to the rotating motion of the crank. The design of the crankshaft also establishes the length of the piston stroke because the radial offset of each throw is equal to half the stroke conveyed to the piston.
- Valves, Pushrods, and Rocker Arms
Located overhead, on one side, on one side and overhead, or on opposite sides of the cylinder, are valves for controlling intake and exhaust. They are called poppet or mushroom valve. They are consisting of a stem with one end enlarged to form a head that permits flow through a passage surrounding the stem when raised from its seat. It prevents flow when the head is moved down to contact the valve seat formed in the cylinder block.
The pushrod is operated by cams which opens and closes the valves in the internal combustion engine. To assure proper closing of the valves, clearance must be maintained between the ends of the valve stems and the filter mechanism. This can be done by providing pushrod length adjustment or by using hydraulic filters.
Camshaft is responsible for opening and closing the valves. It is driven from the crankshaft by a chain drive or gears on the front end of the engine. One turn of the camshaft completes the valve operation for an entire engine cycle. The camshaft is located above and to one side of the crankshaft, directly under the valves of the pushrods that extend down from the rocker arms of the valve-in-head engine.
It is consisting of a heavy circular cast-iron disk with a hub for attachment to the engine. It can oppose all changes in its rotational speed because its heavy rotating mass has sufficient momentum. It can also force the crankshaft to turn steadily at a fast speed. It allows the engine to run smoothly without rotational pulsations.
The crankshaft contains bearing surfaces on each cranks throw and three or more main bearings. All engines, except the smallest ones use split-shell bearings that are usually made of bronze with Babbitt metal linings. Smallest engines on the other hand have Cast-Babbitt bearings.
- Ignition System
Ignition is the process of starting combustion of fuel in the cylinders of the engine. There are two types of ignition systems. The electric ignition system or magneto, and the battery-and-coil system.
The magneto only requires the spark plugs and connecting wires to complete the system. The battery-and-coil ignition system on the other hand requires several separate components such as a distributor, a battery, a coil, and a circuit breaker.
- Spark Plugs
An important component of the ignition system is the spark plug. It is the part that must operate under the most severe conditions. It is usually the shortest-lived component of the gasoline engine because it is exposed to the temperatures and pressures of the combustion chamber. It is responsible for firing the explosive mixture, or fuel in the engine.
The carburetor in a gasoline engine is a device that introduces fuel into the airstream as it flows into the engine. It mixes vaporized fuel with air to produce a combustible mixture.
The supercharger is a device in a gasoline engine which increases the pressure of the fuel-air mixture. It is used to achieve greater engine efficiency. It uses a pump or blower to raise the pressure of the air supplied to the cylinders and increase the weight of charge.
- Cooling System
The cooling system prevents the gasoline engine from overheating. Gasoline engines require cooling because it cannot convert all of the energy released by combustion into useful work. When the cooling system is in working order, the engine can run idle all day without overheating.
- Lubrication System
The lubrication system of the gasoline engine decreases friction by placing a film between the rubbing parts. The lubricants that are commonly used are developed from crude oil after the fuels have been removed.
- Exhaust System
An exhaust system is a piping that is used to guide the reaction exhaust gases away from a controlled combustion inside the engine. It conveys burnt gases from the engine and includes one or more exhaust pipes.
It’s amazing to know that the engines of our gasoline cars are composed of different parts that work together to give our automobiles excellent performances. Now that we know the primary components of a gasoline powered engine and their functions, we will be able to tell which part needs to be checked when we experience some problems with our cars’ engine.