An automobile is a typically four-wheeled vehicle with an internal combustion engine that runs on volatile fuel. It is primarily intended for passenger transportation.

Design of automobiles 

The main parts that make up a car. The modern car is a sophisticated technical system made up of subsystems that serve particular design purposes. Some of these are made up of thousands of individual parts that have come about as a result of innovations in both new and old technologies, such as electronic computers, high-strength polymers, and new steel and nonferrous metal alloys. Certain subsystems have emerged due to various concerns, including safety regulations, air pollution, and global manufacturer competitiveness. 

With an estimated 1.4 billion passenger automobiles on the road globally, passenger cars have become the main mode of transportation for families. Approximately 25% of them are in the United States, where annual travel exceeds three trillion miles (almost five trillion kilometers). Approximately half of the hundreds of models given to Americans in recent years have come from foreign makers. In an effort to profit from their in-house developed technologies, manufacturers are releasing new designs on a regular basis. Approximately 70 million new units are produced annually globally, allowing manufacturers to divide the market into numerous, highly profitable sub-sectors.

It is widely acknowledged that the secret to competitive success is new technical innovations. All automakers and suppliers have engaged engineers and scientists for research and development to enhance the body, chassis, engine, drivetrain, control systems, safety systems, and emission-control systems. 

There are economic ramifications to these remarkable technological developments. According to a study by Ward's Communications Incorporated, mandatory safety and emission-control performance requirements (like the addition of air bags and catalytic converters) caused the average cost of a new American car to increase by $4,700 (in terms of the dollar's value in 2000) between 1980 and 2001. In the years that followed, new criteria were nevertheless put into place. Another factor pushing up car prices was the introduction of computer technology, which climbed by 29 percent between 2009 and 2019. This is in addition to the consumer costs associated with engineering improvements in fuel economy, which may be offset by reduced fuel purchases.

The intended purpose of a vehicle greatly influences its design. Off-road vehicles need to be robust, straightforward machines that can withstand harsh overloads and difficult operating conditions. On the other hand, goods meant for high-speed, restricted-access road systems need to have better high-speed handling and vehicle stability, as well as greater options for passenger comfort and engine performance. The distribution of weight between the front and rear wheels, the height of the center of gravity and its location in relation to the vehicle's aerodynamic center of pressure, the suspension setup, and the choice of wheels for propulsion are the main factors influencing stability. Weight distribution is mostly determined by the engine's location and size. Front-mounted engines are commonly used, which takes advantage of the stability that is

The Body 

Car body designs are often divided into groups based on the number of doors, the configuration of the seats, and the roof structure. Car roofs are typically supported by pillars on both sides of the body. Retractable fabric top models that are convertible depend on the pillar beside the windshield to provide upper body strength because the mechanisms and glass areas are essentially nonstructural. More glass has been added for convenience and style.

It is not feasible for manufacturers to generate entirely new designs every year due to the high expense of new industrial tools. Generally, entirely new designs are scheduled in cycles of three to six years, with only minor adjustments made at that time. A fully new design used to need up to four years of planning and new tool purchases. It is now possible to cut this time requirement by fifty percent or more by using computer-aided design (CAD), computer-aided manufacturing (CAM), and testing through the use of computer simulations.

Sheet steel is often used to make automotive bodywork. To enhance its capacity to be shaped into deeper depressions without wrinkling or ripping in manufacturing presses, the steel is alloyed with different elements. Steel is employed because it is inexpensive, widely available, and easily worked. However, because to their unique qualities, some materials—like aluminum, fiberglass, and carbon-fibre reinforced plastic—are utilized for specific applications. Plastics made of polyamide, polyester, polystyrene, polypropylene, and ethylene have been engineered to have higher toughness, resistance to brittle deformation, and dent resistance. Body panels are made of these materials. Compared to steel components, tooling for plastic components is typically less expensive and takes less time to develop, allowing designers to make changes at a reduced cost.

Special priming and painting procedures are employed to keep bodies strong and aesthetically pleasing while shielding them from corrosive environments. To get rid of oil and other unwanted objects, bodies are first submerged in cleaning baths. After that, they cycle through a series of dip and spray operations. Both enamel and acrylic lacquer are frequently used. Hard-to-reach regions can be covered and an even coat applied by using the technique known as electrodeposition, which involves charging the paint spray with an electrostatic charge and then drawing it towards the surface with a high voltage. The firm uses ovens with conveyor lines to expedite the drying process. Body portions are constructed from corrosion-resistant stainless steel and galvanized steel with a protective zinc coating that are more likely to corrode.

Framework 

Up until the middle of the 20th century, the engine, wheels, axle assemblies, transmission, steering system, brakes, and suspension parts were all mounted on a pressed-steel chassis, which served as the vehicle's skeleton. The body-on-frame construction method was used during the manufacturing process, where the body was flexibly bolted to the chassis. Heavy-duty vehicles, like trucks, benefit from having a strong central frame because it can withstand the forces involved in carrying freight and absorb engine and axle movements that are permitted by the combination of body and frame. This process is currently used for these types of vehicles.

The body and the chassis frame are integrated into a single structural component in contemporary passenger automobile designs. In this configuration, referred as The steel body shell of a unit-body (or unibody) construction is strengthened with braces to provide it the necessary rigidity to withstand applied forces. For improved noise-isolation qualities, certain cars have been equipped with partial "stub" frames or separate frames. Modern component designs tend to use heavier-gauge steel, which absorbs impact energy and limits infiltration in the event of an accident.

Engine 

Numerous engines have been employed in both vehicle manufacturing and experimentation. Diesel engines are frequently utilized in trucks and buses, but gasoline-fueled reciprocating piston internal combustion engines, which run on a four-stroke cycle, have proven to be the most successful for cars. The gasoline engine was first chosen for cars because it could run more adaptably over a wider speed range, developed a reasonable amount of power for a given weight engine, could be produced economically through mass production, and used a reasonably priced, easily accessible fuel. Later on, operational range, exhaust emissions, compact size, and reliability all became crucial considerations. 

These goals are always being reevaluated, with a focus on reducing greenhouse gas emissions (see the greenhouse effect) or traits that cause pollution of power systems for automobiles. This has sparked renewed interest in internal combustion engine improvements and alternative power sources, which were previously far from economically viable. Today, there are a number of battery-powered electric vehicles available in limited production. They have not demonstrated their competitiveness in the past due to operating characteristics and costs. Hybrid power systems, which integrate gasoline or diesel engines with battery systems and electric motors, have emerged as a threat to the gasoline engine in recent years, despite improved emission-control devices designed to improve emission performance. But these designs are more expensive since they are more complicated.

The development of more powerful engines in the US led for larger cars (with horsepower ratings up to roughly 350), the industry is moving away from lengthy, straight engine cylinder layouts and toward compact six- and eight-cylinder V-type layouts. Smaller four-cylinder engines are required for smaller automobiles. The range of European car engines was far greater, with 1 to 12 cylinders and associated variations in weight, cylinder bores, piston displacement, and overall size. Most of the versions had four cylinders and were rated for up to 120 horsepower. The majority of engines featured inline or straight cylinders. However, there were a number of V-type models and two- and four-cylinder makes that were horizontally opposed. It was common to use overhead camshafts. The smaller engines were usually air-cooled, mounted in the back of the car, and had low compression ratios. Growing enthusiasm for better fuel efficiency resulted in a To increase economy, go back to smaller V-6 and four-cylinder configurations with up to five valves per cylinder. Manufacturers worldwide have succeeded in lowering emissions and increasing performance using variable valve timing. When engine speeds and loads vary, electronic controls automatically choose the more efficient of two profiles on the same cam.

Fuel 

Diesel fuels are utilized for many trucks, buses, and cars, and compressed liquefied hydrogen has been employed in experiments, but specially blended gasoline is practically the only fuel used for driving autos. The most crucial characteristics of a gasoline for usage in cars are its appropriate volatility, adequate antiknock quality, and lack of harmful combustion byproducts. Refiners adjust the volatility on a seasonal basis to ensure that enough gasoline vaporizes—even in very cold weather—to facilitate simple engine starting. The gasoline's octane number is used to rate the quality of antiknock. An automobile engine's required octane number is mostly determined by its compression ratio, however other factors include combustion chamber design, engine system maintenance, and deposits on the chamber walls. In the 21st century regular gasoline carried an octane rating of 87 and high-test in the neighbourhood of 93.

Manufacturers of automobiles have pushed for laws requiring cleaner-burning gasoline’s to be refined in order to increase the efficiency of emission-control equipment. This type of gasoline was initially sold at a few service stations in California. Starting in 2017, the major gasoline importers and refiners in the US were mandated to reduce the average amount of sulfur particles in their fuel to 10 parts per million. 

Natural gas-powered car fleets have been on the road for a while now. Emissions of particulate matter and carbon monoxide are cut by 65–90%. For equivalent cars to have the same driving range, natural gas fuel tanks need to be four times larger than gasoline tanks. Cargo capacity is harmed by this.

Lubricant 

An automobile's moving parts all need to be lubricated. Friction without it would lead to higher power consumption and component damage. In addition, the lubricant reduces noise, acts as a coolant, and seals the gap between engine piston rings and cylinder walls. A gear-type pump is part of the engine lubrication system, which uses drilled passageways to distribute filtered oil under pressure to different bearings. The cams and valve lifters are lubricated by oil spray as well. 

Some chassis joints require a light grease that may be injected using pressure guns; wheel bearings and universal joints demand a very stiff grease. In order to withstand severe loads, manually shifted transmissions use a heavier gear oil comparable to that used for rear axles, while hydraulic transmissions require a specific grade of light hydraulic fluid on the gear teeth. Gears and bearings in lightly loaded components, such as generators and window regulators, are fabricated from self-lubricating plastic materials. Hydraulic fluid is also used in other vehicle systems in conjunction with small electric pumps and motors.

Electrical System

The electrical system of an automobile consists of a storage battery, generator, starting (cranking) motor, lighting system, ignition system, and various accessories and controls. Initially, the electrical system of an automobile was limited to the ignition equipment. Electric lights and horns replaced kerosene and acetylene lights and bulb horns with the introduction of the electric starter on a 1912 Cadillac model. Electrification was rapid and complete, and by 1930, 6-volt systems were standard everywhere. The larger engines required higher cranking torque. Additional electrically operated features—such as radios, window regulators the late 1950s around the world.

The spark needed to ignite the fuel-air mixture in the engine's cylinders is supplied by the ignition system. The spark plugs, coil, distributor, and battery make up the system. To bridge the spark plug electrode gap, the electrical system's 12-volt potential needs to be increased to around 20,000 volts. This is accomplished using a circuit that begins with the battery, one side of which is grounded on the chassis, travels through the ignition switch to the ignition coil's primary winding, and then uses an interrupter switch to return to ground. A high voltage is induced across the coil's secondary terminal when the primary circuit is disrupted. The coil's secondary high-voltage terminal connects to a distributor the spark needed to ignite the fuel-air mixture in the engine's cylinders is supplied by the ignition system. The spark plugs, coil, distributor, and battery make up the system. To bridge the spark plug electrode gap, the electrical system's 12-volt potential needs to be increased to around 20,000 volts. This is accomplished using a circuit that begins with the battery, one side of which is grounded on the chassis, travels through the ignition switch to the ignition coil's primary winding, and then uses an interrupter switch to return to ground. A high voltage is induced across the coil's secondary terminal when the primary circuit is disrupted. The coil's secondary high-voltage terminal connects to a distributor.

Transmission 

When starting and stopping, the gasoline engine needs to be uncoupled from the driving wheels. This feature means that, once the engine has been started, some kind of unloading and engaging device is required to allow for the slow application of load. The engine's torque, or turning effort, is minimal at low crankshaft speeds and reaches its maximum at a rather high speed that corresponds to the engine's rated horsepower. 

An vehicle engine operates most efficiently when it is under heavy load and the throttle is almost fully opened. An automobile needs only a small portion of this power to move forward at modest speeds on flat roads. When driving normally and at a steady, moderate speed, the engine may operate at an uneconomically light load unless some means is provided to change its speed and power output.

The sliding-spur gear type, which has three or more forward speeds in addition to reverse, is the most basic type of automotive transmission. By adjusting a shift lever, which engages the different gears by sliding a spur gear into the correct position, the desired gear ratio can be chosen. In order to engage and disengage gears throughout the selecting process, a clutch is needed. A transmission that is automated removes the need to learn how to use a clutch. A hydraulic torque converter, which transmits and amplifies engine torque, is used by the majority of automatic transmissions. Every kind allows for the manual option of low and reverse ranges, which either use lower gear ratios than typical driving or prohibit automated upshifts. Occasionally, grade-retard options are also incorporated to provide dynamic engine braking on hills. Automatic transmissions not only require little skill to operate but also make possible better performance than is obtainable with designs that require clutch actuation.

Transmissions that are continuously (or indefinitely) variable offer a very effective way to transfer engine power while also automatically adjusting the effective input-to-output ratio to maximize economy by maintaining the engine operating within its optimal power range. The majority of designs use two variable-diameter pulleys joined by a high-strength rubber V-belt or a steel one. An electrohydraulic actuator can alter the effective diameters of the split pulleys, hence adjusting the transmission ratio. This enables the electronic control unit to choose the best ratio for minimizing emissions and maximizing fuel economy across all engine speeds and loads. These devices were initially only meant for tiny automobiles, but belt advancements have allowed them to be used with larger vehicles.