Car Engine

Car Engine: - All power plants, with the few exceptions, are mounted in the forward end of the frame. The transmission is considered part of the power plant, since it governs or controls the ratio of speed and power which may be delivered to the rear axle. The engine drives the transmission, and the transmission turns the propeller shaft.

V-8 power plant (Ford V-8 engine and accessories).

• A transmission
• B breather
• C fuel pump
• D air cleaner
• E carburetor
• F generator
• G fan
• H intake manifold
• I exhaust manifold
• J starter
• K water pump
• L timer distributor
• M rubber engine mount
• N cylinder block
• 0 oil pan
• P cylinder head

The speed of the propeller shaft depends on the gear in which the shift lever is set. In high, the ratio through the transmission is 1 to 1. In low, the ratio is about 3 to 1. Low and intermediate give greater turning power (torque) to the propeller shaft than high, but the speed of the car is cut down. These points are mentioned thus briefly to show that the power plant rightfully includes this unit which transmits the power of the engine at varying speeds. Likewise, the clutch belongs to the power plant.

The most favoured method is to build engine, clutch, and transmission together as a unit, and mount the unit power plant in the car frame in a manner calculated to prevent engine vibrations being transmitted to the car interior. Rubber-lined mounting blocks, are used to check engine vibration.

For many years either three- or four-point metallic contact mounting was used for the unit, power plant, both being popular with the manufacturers. The later use of the rubber engine-mounting blocks reduced the amount of vibration carried to the driving compartment.

Chrysler engineers learned that by mounting an engine at two points, so that the centre of mass or centre of gravity was approximately on a line between the two bearings (one well up on the front of the engine and the other under the transmission case), engine vibration could be still further reduced. The rocking or torque reaction of the engine under load was first absorbed by a leaf spring but later this spring was replaced by rubber blocks which were found more effective. There are many variations of power-plant mounting, most of which make use of some form of rubber mountings.

Just as the units of the chassis were considered, it is desired to separate and study the functions of the units composing the power plant on this page. Next, the individual units going into an engine are studied, and in the individual parts of the various other units of the power plant are discussed in detail. On this page, it is desired to familiarize with the names and locations of the various units going into the make-up of a complete power plant. The duties falling to the lot of each accessory or unit will be discussed briefly.

Engine: -

The water pump and oil pump appear on the left side of the engine, and are considered a definite part of the engine. A fan-drive pulley appears on the forward end of the pump shaft. A fan mounting bracket is provided.

The right-side view of the engine shows the starting motor bolted to the flywheel housing. This starter, when removed, exposes the teeth of the flywheel ring gear to view. The screw mounting holes are made in accordance with S.A.E. specifications.

When the starting-motor manufacturer builds his equipment, it is built according to the same specifications, and a fit is thus assured. The manifold is a part of the engine, but the carburetor is an accessory. The intake and exhaust manifolds are cast together in some instances. A flange is left at the centre of the manifold. This flange is machined to allow the carburetor to be fitted to it.

Carburetor: -

An engine, such as is used in automobile service, is termed an internal-combustion engine. This means that the fuel is burned within it. The point where the fuel is burned is called the combustion chamber. This space is above the piston in the cylinder head and around the valves, and naturally includes that portion of the cylinder exposed as the piston is driven down.

The fuel used in engines is, for the most part, gasoline or similar fuel. The burning process is ordinarily termed firing or exploding the gas. The fuel, that is, the gasoline, in order to be burned or "exploded" within the combustion space, must first be passed through the carburetor where it is mixed with air. Next, it must be drawn into the combustion space, and then it must be compressed after which it is fired by the electric spark.

The function of the carburetor is to mix the fuel and air. In order to mix the gasoline with the air, the gasoline must be sprayed into the air which is rushing through the carburetor on its way into the engine. The early carburettors were called mixing valves.

Gasoline is furnished the carburetor from the main supply tank by means of a fuel pump, a vacuum tank, gravity feed from the main supply tank, or air pressure. Carburetor engineers spend much time designing and testing their product for motor-car manufacturers.

Timer-distributor and coil : -

It is the function of the ignition set to deliver a spark to the spark plug at the approximate moment when the compression is greatest. All timer-distributors are manufactured to S.A.E. specifications. The car manufacturer selects the equipment which he desires, or he may have the electrical-equipment factory build it after a specified design.

An ignition set may be either self-contained as in the case of the high-tension magneto used on some busses, trucks, marine engines, racers, and aircraft engines, or it may be composed of several units. Every ignition set has three major parts. These are the timer, the distributor, and the coil .

Spark plugs: -

The purpose of the spark plug is to receive the high.. tension spark or current from the distributor (through the spark-plug cable), and conduct it to the combustion space, where it fires the charge as it jumps the air gap of the plug. It must be made most carefully in order not to break down in the intense heat of the exploded gases. Ordinarily, one plug per cylinder is used by the manufacturer, but two plugs may be used. When more than one plug is used in a cylinder, it is with the idea of preventing failure and also securing quicker ignition.

Generator: -

Passenger cars are dependent on the storage battery for their ignition and lighting as well as electric cranking. The battery would quickly be exhausted were it not for the generator which is constantly building up or charging the battery when the engine is operating above an idling speed. Different methods are used to drive the generator. Unlike the timer-distributor, it is not necessary to drive the generator at a definite speed relation with the engine.

Starting motor: -

Hand cranking was for many years a factor in limiting the use of passenger automobiles. Special spring starting devices, gas starters, and air starters were designed to relieve the driver of this arduous and dangerous task. When Mr. Chas. F. Kettering, Vice-President of General Motors, in Charge of Research, invented and perfected the system of electric cranking of automobiles, he performed a wonderful service for both car manufacturers and the general public.

Starting motors are designed to turn the engine over at speeds in excess of those possible by hand cranking. They are connected to the engine while cranking it, and then are automatically disengaged when the engine starts to operate under its own power. Starting motors, although small, are assigned heavy duties.

Clutch: -

There are a number of types of clutches. Cone clutches were very popular at one time. Disk or multiple-plate clutches were used in many passenger vehicles. Single-plate clutches for light cars and double-plate clutches for the heavier cars are in general use.

Clutches are provided with a clutch-pressure plate which moves or is made to turn with the flywheel at all times. A plate is fastened to the clutch shaft, and this connects with the transmission shaft. When the clutch is held in the "out" position, the clutch-pressure plate on the flywheel is free to turn with it, but does not cause the plate fastened to the clutch shaft to turn.

Transmission: -

The connection of the transmission with the power plant was discussed at the first part of this chapter. Transmissions are made by manufacturers ,of cars in many instances ; but very often they are built by factories which have had long experience in building gears for this special service.

Transmission gears are subject to as severe use as, and worse abuse than, any other part of the automobile with the possible exception of the clutch. However, these two items are used in connection with each other, and each must stand much abuse from inexperienced and incompetent drivers. The transmission gears are the only gears about the motor car which are not as a rule in constant mesh. Gear shifting means demising and meshing of the teeth of the driving and driven gears except where shifting dogs or dog clutches are used.

In case of unsuccessful shifts, or shifts which are only partially completed before the clutch is let in, the teeth of the transmission gears are subject to abuse. Clashing and grinding gears is abuse. A driver, who is untrained in shifting, and who fails to understand or heed instruction, will ruin the best gears it is possible to make. In his hands, gears, which should give service for the life of the car, are ruined in a few thousand miles. As designed by the builders, the transmission gears are amply strong, if not abused.

Fan: -

Engines are provided with fans, to draw the air through the radiator when the engine is operating. Heat from the engine must be passed off into the air. The water in the engine water jacket carries it to the radiator, and the air passing through the radiator conducts the heat out of the fins and tubes. Fans are usually made up by shops which cater to the car manufacturers, by producing some of the smaller parts for them. Belts are used as a rule for fan drive. Adjustment of the fan bracket is provided in order that the fan belt may be kept at proper tension.

Engine accessories: -

Figure on top of this page illustrates a number of the usual engine accessories. Most engines are fitted with an air cleaner which may also be designed as a flashback screen or fire preventer or an intake-roar silencer. The carburetor on this engine is downdraft.

The exhaust manifold has a centre outlet for tail-pipe connection. The intake manifold has a section interlocking the exhaust manifold so as to receive heat there from. The oil pump is driven from the camshaft and is easy of access from the side of the engine. The oil cleaner is attached to the engine near the oil pump and just to the rear of the fuel pump which is driven by the engine from the camshaft. The fan is mounted on the water-pump shaft and is belt-driven.

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