9. Fill in the correct prepositions.

1. He can rely ___ me to maintain your car.

2. The advantages ___this system are too numerous to mention.

3. ___ general, Japanese cars are very reliable and breakdowns are rare.

4. The new invention had wide application ___ industry.

5. Motorcars can be classified ___ many kinds.

6. Illegally parked vehicles will be removed ___ the road.

7. They noticed the difference ___ these two engines ___ once.

8. Transmission is the system ___ a motor vehicle by which power is transmitted ___ the engine ___ the wheels.

Part II

10. Read text b carefully. Pay attention to the words in bold type.

B. Valves and Camshaft. Electrical System

The air-fuel mixture enters a combustion chamber, or cylinder, of the engine whenever the corresponding valve is opened. The opening and closing of the valves are accomplished by the camshaft, which turns with the engine. In most engines projections on the camshaft raise a pushrod that is connected with a valve. In the overhead valve engine the pushrod moves the rocker arm, which in turn opens the intake valve. As the cam continues to turn, the pushrod moves down again, and the intake valve closes. The exhaust valve operates on the same principle.

Instantaneous ignition of the explosive air-fuel mixture in each cylinder of the engine requires a strong, hot electric spark. This spark is caused by a momentary surge of high voltage, which may reach 20,000 to 25,000 volts. The voltage is supplied by a small induction coil. The surge occurs when the flow of electricity in the primary winding of the induction coil is interrupted by the opening of a breaker arm. A rotor permits the high-voltage surge to pass to each spark plug and trigger combustion in the cylinders in precisely timed sequence.

The ignition system, as well as lights and other electrical devices in the car, is supplied with current from a 6- or 12-volt storage. The battery is charged during operation of the vehicle by a direct-current (DC) generator powered by the engine. A variation of the generator, called an alternator, or alternating-current (AC) generator, has been developed. The AC is changed, or rectified, to DC by means of a diode, or type of electron tube. Unlike the ordinary car generator, the alternator continues to charge the battery while the engine is at its lowest, or idling, speed. The storage battery also powers the starter. This is an electric motor that cranks, or turns, the engine until the spark plugs ignite the air-fuel mixture. The ability of gasoline to operate at a specified compression ratio is measured in octane ratings. Gasoline rated too low for a specified engine may ignite prematurely and produce a pinging sound, called knock.

Another cause of engine knock is accumulation of soot (carbon) as a hard deposit inside the cylinder. Pieces of carbon become red-hot and act like a spark to cause premature ignition. Occasionally running the engine at high speed or driving the car at maximum highway speeds does much to avoid or clean out this accumulation of carbon. Missing is a term used to describe failure of the air-fuel mixture to ignite. It may be caused by a cold engine. The compression ratio is a good indication of engine performance. The greater the ratio of an engine, the more power it delivers per unit of fuel.

The cylinders of the engine are moulded into a cylinder block, a heavy block of metal. The cylinder head is a separate casting that is bolted to the block. Most cylinder blocks and heads are made of cast iron, though some are made of aluminium.

Comprehension Check 2