The Automobile Engine.

[Music] the automobile and the truck more than 72 million of them taking us to work or to play millions of them taking us down city streets turnpikes and Country Roads taking us around the continent or around the block taking us across Finish Lines or across town on every imaginable kind of erand millions of engines providing the Motive Power engines so reliable and so taken for granted that few people ever wonder how they work and yet even a fundamental knowledge of engine operation can add substantially to our enjoyment of Motoring and our safety what are the facts behind this amazing power and dependability what happens under the hood when with complete confidence we turn the ignition key the source of power in most cars and trucks today comes from an internal combustion engine requiring fuel to burn a spark to ignite the fuel a lubrication system to reduce friction and a cooling system to dissipate any unwanted heat inside this engine are compartments called cylinders at regular intervals within each cylinder a charge of air and vaporized gasoline is introduced and ignited this fuel air mixture Burns rapidly generating tremendous heat which causes the trapped gases to expand and thus create power here is one cylinder in outline inside is a close- fitting smaller cylinder called a piston the area between the piston and the top of the cylinder is the combustion chamber at the top of the cylinder are two openings or ports one is the intake Port through which the fuel air mixture enters the combustion chamber the other is the exhaust port for which the burned or exhaust gases leave the chamber also at the top of the cylinder is the spark plug which as part of the ignition system reduces the spark to ignite the fuel air mixture the expanding force of the ignited mixture drives the Piston down this vertical movement of the Piston is converted into rotary motion by the connecting rod turning the crankshaft the transmission the drive shaft the axle and finally the wheels now let's start the engine we turn on the ignition key an electric starter motor turns the crankshaft the connecting rod pulls the Piston downward thus creating a low pressure area above the Piston atmospheric pressure pushes the fuel air mixture into the combustion chamber this is called the intake stroke notice the intake valve closes at the bottom of the stroke thus trapping the fuel air mixture the starter still engaged turns the crankshaft so the Piston moves upward compressing the fuel air mixture and thus making it more potent this is called the compression stroke as the Piston reaches the top of the stroke the spark plug ignites the compressed fuel air mixture the rapid expansion of gases forces the Piston downward and now the engine is operating under its own power releasing the starter this is the power stroke the momentum of a flywheel keeps the crankshaft turning to push the Piston up again at the same time the exhaust Port opens to allow the burned gases to escape this is the exhaust stroke our single cylinder has now completed the basic cycle of four strokes and is ready to repeat treat them intake compression power exhaust our Pistons you notice must be free enough in the cylinder to allow unobstructed movement too much free play however would allow the expanding gas to slip through unless we add seals called piston rings these Rings rest in grooves cut in the piston and press against the cylinder wall effectively preventing power loss now we must answer the question how do the intake and exhaust ports open at precisely the right times during the cycle this we accomplish by a series of mechanical hookups called a valve train which enables the movement of the crankshaft to regulate the movement of the valves here's how it's done the crankshaft turns another shaft called the cam shaft this is designed with an eccentric for each valve an eccentric is a disc shaped somewhat like an egg as the cam shaft revolves The Eccentric forces the push rod upward which lifts one end of the rocker arm moving the other end downward and forcing the spring-loaded valve to open as the cam shaft continues to revolve pressure is released and the spring forces the valve to close the cam shaft is timed with the crankshaft so as the Piston starts down on the intake stroke the intake valve opens at the bottom of the stroke it closes the exhaust valve begins to open when the Piston starts up on the exhaust stroke and closes at the top of the stroke both intake and exhaust valves remain closed during the compression and power strokes Direct affecting the power output of the cylinder is the compression ratio a term used to describe the relationship of cylinder volume when the Piston is down say it's 80 cubic in to the volume remaining when the Piston is at the top of its stroke say it's 10 cubic in the ratio here is 80 to 10 or 8 to one the greater the ratio or the more the fuel air mixture is compressed the faster it burns and expands and the greater the power of the engine another factor that affects engine power is displacement this is the total volume of the distance traveled by all Pistons we figure cubic in displacement by multiplying the circular area of the bore say it's 12.57 Square in by the length of the Piston stroke say it's 3.5 in and multiplying that by the number of cylinders eight total displacement 351.5 larger displacement engines produce more power at the same number of revolutions per minute so far we haven't shown how the fuel is introduced except to say that it comes in through the intake Port but there's quite a story in the preparation and control of the fuel before it enters the combustion chamber to burn with the necessary explosive force the gasoline must first be vaporized that is mixed with air and in the right proportion usually about 15 Parts air to one part fuel this is the job of the carburetor a Precision engineered device designed to deliver the required amount of fuel for any particular driving speed gasoline is delivered from the fuel tank to the carburetor by the fuel Pump It enters the carburetor float chamber which maintains a constant level of fuel at all times the float chamber has a restricted passage that leads to an air horn open at the top to receive the air and narrow in the middle to intensify the air flow the narrow part is called the Venturi on the intake stroke the Piston goes down and forces air through the horn toward the combustion chamber at a tremendous speed gasoline is pulled into the air flow and mixed with it the amount of the mixture entering the cylinder is controlled by a throttle plate and this regulates the engine speed the vaporized gasoline rushes into the combustion chamber ready to be compressed and ignited more sophisticated versions of the simple one Venturi carburetor are the two Venturi or dece and the modern four Venturi or quad these provide more fuel more air and consequently more power when needed and that brings up another important question how do we ignite the fuel air mixture well the spark plug we mentioned earlier contains two wires or electrodes with their tips just close enough together for a spark to jump from one to the other now the source of the electrical energy which produces the spark is a storage battery located within the engine compartment now while battery current is the electricity which feeds the spark plug voltage is the pressure that moves the current but the truth is that the voltage supplied by the 12vt battery is not strong enough by itself to jump the spark plug gap we must provide a means of getting More Voltage than that supplied by the battery alone we do this by adding an ignition coil A Step up Transformer which in this case transforms the low 12vt current from the battery into a high 15,000 volt current the low or primary current travels around several windings of insulated wire and returns to the battery this primary current does not go directly to the spark plug however inside the primary coil is a secondary coil many windings of extremely fine wire around an iron core if we interrupt the primary current momentarily a high voltage is induced in the secondary windings a current of 15,000 or more volts goes into the spark plug jumps the Gap and thus creates the spark that ignites the fuel it's obvious of course that there has to be a timing device or Breaker Point for interrupting the primary circuit and inducing the high voltage at the top of the compression stroke this device is a switch controlled by the movement of the cam shaft it is adjusted so that at the top of the compression stroke the primary current is Switched Off and the secondary takes over after initiating combustion the switch turns the primary back on and the secondary goes off this onoff process continues as long as the engine is running and that basically is how the four cycle internal combustion engine operates even though we expand our one cylinder to four six or eight cylinders each cylinder operates on these same principles although with many refinements and accessories in today's multi-cylinder engines the cylinders are not separate units as they were once but have been cast together in a block actually the block is an iron box containing a series of holes these holes are the cylinders this is called a V8 block because two rows of four cylind ERS each are set at a B angle the V8 engine has two cylinder heads one for the top of each Bank of cylinders the cylinder heads contain an intake and exhaust valve for each cylinder and a valve rocker arm assembly for each valve cavities in the head combine with the cylinders and the block to form the combustion Chambers now let's take a look at a complete engine in cutaway form let's turn it on each piston has its connecting rod leading to One Long crankshaft notice that the offsets or throws of the crankshaft are so arranged that there is always one piston delivering power one exhausting gases one drawing in the fuel air mixture and one compressing it if the Cycles were not staggered in this way engine operation would be rough indeed this crankshaft also has counterweights designed to reduce reduce engine vibration and the load on the main bearings the flywheel is a balanced heavy metal disc fastened to the rear of the crankshaft its momentum keeps the crankshaft revolving evenly between power strokes in the multi-cylinder engine the cam shaft has an eccentric or lobe for each valve this large pan-like device houses an air cleaner air entering the engine is filtered of dust and other forign substances that might otherwise cause engine failure the ignition system of the V8 engine operates on the same Principle as that described for the single cylinder model except that now it must provide voltage for eight spark plugs instead of one again this requires the use of a switch commonly called a distributor in place of the simple Breaker Point the rotary switch also powered off the cam shaft breaks the primary current thus inducing the high voltage secondary current which it then directs to eight contact points Each of which leads to one of the eight spark plugs the breaker points are timed to function when each piston reaches the top of the compression stroke our engine is able to run now but it won't run for long without the help of a lubrication system which pumps oil to every area of the the engine Where Metal moves against metal nor will it operate long without a cooling system which carries off excess heat so our engine has been fueled ignited lubricated and cooled now it really is able to run for a long time too and like hundreds of its kind coming off the assembly lines every day in different sizes different degrees of power it symbolizes a way of life based on Mobility engine improvements across the years provide a story of engineering progress that is almost without equal memorable Milestones 1908 the fabled Model T the first successful attempt to cast a four cylinder engine block in one piece for quantity production an important Foundry practice breakthrough 1928 the much improved Model A both were legendary for their performance and reliability 1932 for the first time a method was developed for the mass production casting of a solid V8 engine block thereby making it possible to build V8 performance into high production low priced cars in the 1960s techniques have been developed to cast engine blocks with much greater Precision thinner th walls and less weight and they're easier to cool as a result the thickness of the engine walls has been reduced by about 16% in a 500 lb engine this represents a savings of about 80 lb in weight with modern metals and reinforcement techniques today's engine blocks are even stronger than the thick cast walls of yesterday in keeping with today's high standards of quality workmanship testing too is more exacting than ever testing on the dynamometer to prove out engineering objectives such as power output fuel economy durability and reliability and on the hot test stand where every production engine is run before being installed in a new car and is electronically balanced with a degree of precision far beyond that which was possible only a few years ago out of such testing come engines that will contribute to the car's total performance the better engines of today and the still better engines of Tomorrow engines that do more than turn Wheels engines with power to spare for such modern conveniences as power steering power braking power seats air conditioning automatic transmissions engines with Reserve power for better control on city streets for that extra margin of safety in passing on the highway for fast economical cross country [Music] travel power mature drivers are grateful for it new drivers must learn to respect it if we are competent and reasonable drivers the automobile engine will always be what it was meant to be a safe Dependable servant with no purpose but to serve our needs and add to our joy of 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