Read, translate and be ready to explain the meaning of the terms

Air bag:A fabric bag that inflates in frontal collisions at around 12 mph or higher to prevent front – seat occupants from hitting the steering wheel, dashboard, or windshield. Air bags are designed to inflate within a fraction of a second, then immediately deflate so the driver's ability to control the car isn't impeded. Until recently, most cars equipped with air bags have had only one, for the driver, housed in the steering wheel hub. Nowadays, more and more cars also carry a passenger – side air bag mounted in the dashboard. By the 1998 model year, all cars must have dual air bags. The next frontier is side air bags, with the occupant's chest area. Volvo's 850 models are the first to offer this feature.

All-season tires: Tread designs that allow water and snow to escape from under the tire for better traction. Ordinary tread designs tend to trap water, causing “hydroplaning”, in which the tire ride on a thin film of water rather than directly on the road. Most all-season tires are designed for soft ride rather than top-notch handling though some tire companies now offer all-season radials that have a high-performance tread.

Anti-lock braking system (ABS):A computer controls braking force to prevent the wheels from locking in a panic stop. This safety feature is designed to reduce stopping distances and improve steering control under braking, particularly in rain, snow, or on icy pavement. Locked brakes produce skids, in which the driver can neither stop nor steer the car. When ABS brakes are applied, the computer senses when a wheel is about to lock up and then “pumps” the brakes many times per second. The driver simply continues to apply steady force to the brake pedal, but the computer allows the wheels to rotate while slowing the car. Unlike cars, most light duty trucks and sport – utility vehicles until recently had only rear – wheel ABS, but four – wheel ABS is quickly becoming the norm.

Direct ignition:Ignition coils, which supply the spark that ignites the air/fuel mixture inside the engine, are mounted directly atop the spark plugs, eliminating the ignition distributor and ignition wires to the plug.

Disc brakes:Brake design in which a caliper squeezes two friction pads against a disc that's attached to the wheel. Considered more efficient than a drum brake, which curved brake press against the inside of the drum to provide braking action. Commonly, discs are used to brake the front wheels (where most of the braking force takes place), and drums are used in the rear – but all-wheel disc brakes are becoming more common, especially.

Double-overhead camshafts:Also called twin-overhead cams. Two camshafts per cylinder bank, with one operating the intake valves and the other the exhaust valves. Double-overhead-cam engines usually have four valves per cylinder: two intake, two exhaust. A V-type engine with one overhead camshaft per cylinder bank is still a single-cam engine.

Electronically controlled suspension:A system that changes the suspension's ride quality to suit road or driving conditions, usually by altering shock – absorber damping or air – spring rates. Some electronically controlled suspension are designed to enhance ride comfort by softening settings for rough roads. Others stiffen settings to improve handling, at the expense of ride quality. Some systems are automatic, with microprocessors sensing inputs from the steering, brakes, throttle, and other sources to determine the suspension setting. Others are adjustable by the driver from the cockpit. Examples are Cadillac's Road Sensing Suspension and the Computer Command Ride system available on the Pontiac Bonneville.

Four-wheel drive:Engine power is delivered to all four wheels. The chief advantage is added traction on slippery surfaces. Disadvantages include a higher purchase price, extra weight, and reduced fuel economy. The most common system is “part-time, on-demand” 4WD which allows the driver to shift from 2WD into 4WD via transfercase lever on the floor or an electric switch on the dashboard. This system is meant for use only on slippery pavement or off road. Some on-demand 4WD systems lack “shift-on-the-fly” capability. That is, they require that the vehicle be stopped and that the front-wheel hubs be locked by hand before 4WD can be engaged.

“Full-time” 4WD can be used on any surface and is of two types: on-demand, in which it can be used when needed, or permanent, in which it is always engaged. The most sophisticated full-time systems use a viscous, or fluid, coupling to sense which wheels need traction and then automatically deliver engine power accordingly. The driver does nothing to engage or disengage the system.

Front-wheel drive:Engine power is transmitted to the front wheels, pulling the car along rather than pushing it. Front-drive eliminates the driveshaft extending from the transmission to the rear-mounted differential, resulting in more passenger and cargo room. And with the weight of the engine over the driving wheels, traction is enhanced.

Horsepower:A measurement of an engine's ability to perform work, measured by a dynamometer. Engines that produce most of their horsepower at relatively low rpm (revolutions-perminute of the crankshaft), 3000 rpm for example, often provide better low speed pickup than engines that develop more horsepower at higher rpm, 5000, for example. Horsepower isn't the only measure of an engine's overall strength. Its ability to produce torque turning or twisting force-also is a key factor.

Intercooler: Found on some turbocharged and supercharged cars. Acts as a radiator to cool air before it enters the combustion chamber. Cooling makes the air denser and increases the power of the ignited fuel/air mixture.

Naturally aspirated engines:Engines that draw air/fuel mixture into their cylinders without the aid of a supercharger or turbocharger.

Overhead-camshaft and overhead-valve engines: Distinguishing feature is placement of the camshaft. The camshaft in either design activates the valves. In an overhead – valve engine (ohv), the camshaft is located in the engine block, below the valves. It activates the valves by means of pushrods and other components. In an overhead-cam (ohc) engine, the camshaft is located in the cylinder head, with the valves mounted below. The ohc design is more expensive to manufacture, but has fewer parts and acts the engine to run more efficiently on the valves, thus allowing the engine to run more efficiently and at higher speeds. Some engines use double-overhead cams (dohc) for still more efficiency.

Passive restraints:Safety features designed to protect occupants in crashes without being actively engaged. The two kinds are “automatic” seat belts and air bags. Associated components may include under – dashboard knee bolsters. Federal regulations require that all 1994 – model cars have passive restraints for both front seating positions. This may include dual air bags or a driver – side air bag in conjunction with an automatic seat belt for the passenger. The most common type of automatic seat belt employs a motorized shoulder belt that travels over the door and a lap on a track be beltthat must be manually buckled.

Performance: An overall evaluation of how a car accelerates, holds the road, corners, and brakes. Good performance enables a driver to merge easily with expressway traffic, pass quickly on 2-lane roads, negotiate turns and bumpy roads with good control, and stop safely. A car can have good performance without being a high – performance or sports car.

Powertrain:All items necessary to transmit power to the wheels: engine, transmission, axles, clutch (manual transmission), torque converter (automatic transmission), differential (rear-wheel-drive car), and driveshaft.

Rear – wheel drive:Only the rear wheels receive power. The most common configuration has the engine mounted in front. Advantages are simplicity and better front/rear weight balance than front-drive cars. Disadvantages include reduced wet – weather traction compared to front-wheel drive and less efficient use of space. Passenger room is reduced because the driveshaft that links the interior, taking up passenger and cargo space.

RPM (revolutions per minute):A measurement of engine speed, based on how fast the crankshaft is rotating. Rpm is displayed on a tachometer.

Supercharger:A supercharger is similar to a turbocharger in that it forces additional air/fuel mixture into the combustion chamber to produce more power. An important difference is that a turbocharger is driven by the engine's crankshaft, and thus reacts more directly to the throttle and without the lag in response found on many turbochargers.

Suspension:The components that support the weight of the road, absorb bums and road shocks, and control forces produced during acceleration, braking, and cornering. Suspensions vary in design and components, but typical parts include springs, shock absorbers, control arms, and stabilizer bars. An independent suspension means each wheel operates independently of the others, so that when one tire hits a pothole, the spring and shock absorber at that corner absorb the bump with minimal effect to the rest of the suspension.

Torque:The amount twisting force generated by an engine, measured at the crankshaft and expressed in pounds/feet. This is different than horsepower. The amount of torque an engine produces affects ability to accelerate and move heavy loads. As with horsepower, engine speed is a factor. An engine that develops 250 pounds/feet of torque at 2000 rpm can accelerate well from low speeds. It also tends to work well with automatic transmission. An engine that produces 150 pounds/feet of torque at 4000 rpm will have to be revolved much higher to accelerate well from low speeds and will have a harder time hauling heavy loads. An engine with poor low – end torque is probably better suited for use with a manual transmission, which gives the driver more control over engine speed. Engines that produce maximum horsepower at high rpm often have little torque at low rpm.

Traction control:Designed to eliminate or minimize tire slippage while accelerating on any surface where traction is poor, such as in snow or gravel. Traction control systems often utilize the same sensors and computer systems as anti – lock brakes. When sensors at the wheel detect slippage, the traction control system can automatically engage one or more remedies, depending on its design. Most systems automatically “pump” the brake at the slipping wheel to minimize slippage. Some systems can also retard the delivery of engine power to keep the wheels from spinning too fast to gain traction. Traction control is most useful on rear – wheel – drive cars, which have less weight over the driving wheels and tend to spin more readily.

UNIT III

Texts for Individual Reading

Read the text. What are the advantages of the car?

Date: 2015-12-24; view: 625