At Chapter 18. Gasoline Engine Operation, Parts, and Specifications

Technician A says that a crankshaft determines the stroke of an engine. Technician B says that the length of the connecting rod determines the stroke of an engine. Which technician is correct?

Technician A only Correct. The crankshaft determines the stroke because the throw of the crankshaft is half the length of the stroke.

Using a higher compression ratio (CR) results in which of the following?

Great power Correct. Using a higher compression ratio delivers greater power.

A(n) __________ engine draws in the air-fuel mixture at atmospheric pressure.

naturally aspirated Correct. A naturally aspirated engine draws in the air-fuel mixture at atmospheric pressure.

Engines used in automobiles are ____________ combustion engines while steam engines are ___________ combustion engines.

internal, external Correct. In automobile engines, combustion occurs inside the engine, making them internal combustion engines. Combustion occurs outside the engine in steam engines, making them external combustion engines.

A horizontally opposed multicylinder engine design, also called boxer or pancake engine design, _________ the vehicle's center of gravity.

lowers Correct. A horizontally opposed engine design helps lower the vehicle's center of gravity.

Torque is expressed in units of ________.

pound-feet Correct. Torque is the rotating force measured as the amount of force multiplied by length of the lever through which it acts. Therefore, its units are force-distance or pound-feet. It is also expressed as newton-meters.

The flywheel end of the engine to which power is applied to drive the vehicle is called the ________ end of the engine while the front of the engine where accessory belts are used is called the ____________ end of the engine.

principal, nonprincipal Correct. The flywheel end of the engine is called the principal end of the engine while the front of the engine where accessory belts are used is called nonprincipal end of the engine.

In a four-stroke cycle, the crankshaft rotates through _______ degrees while the camshaft rotates through ______ degrees for each stroke.

180, 90 Correct. The crankshaft of a four-stroke engine rotates through two complete revolutions or 720 degrees in each cycle. The cycle is divided in four equal strokes, meaning the crankshaft rotates through 180 degrees for each stroke. A camshaft rotates through 90 degrees in each stroke.

A normally aspirated automobile engine loses about _______ power per 1,000 feet of altitude.

3% Correct. According to the Society of Automotive Engineers (SAE), the decline in density of air with rising altitude causes nonsupercharged or nonturbocharged engines to lose 3% of its power for every 1,000-foot or 300-meter rise in altitude.

One cylinder of an automotive four-stroke cycle engine completes a cycle every ________.

720° Correct. The cylinder of a four-stroke engine completes one cycle in every four strokes or two complete revolutions. Since one revolution is 360 degrees, two revolutions are 720 degrees.

How many rotations of the crankshaft are required to complete each stroke of a four-stroke cycle engine?

One-half Correct. Every 1/2 crankshaft rotation will complete one stroke of a four-stroke engine.

An SOHC V-8 engine has how many SOHC camshafts?

Two Correct. A single overhead camshaft (SOHC) design uses one single overhead camshaft. A V-type engine uses two banks or rows of cylinders. A SOHC V-8 engine will have two SOHC camshafts, one for each row of cylinder.

During the power stroke in a four-stroke engine, the intake valve is ________ and the exhaust valve is _______.

closed, closed Correct. Both valves are closed during the power stroke to maximize the heat generated in the combustion chamber, which maximizes the mechanical force applied on the piston.

The chemical energy in fuel is converted to heat by the burning of the fuel at a controlled rate. This process is called _______________.

combustion Correct. The controlled process of converting chemical energy in fuel to heat is called combustion.

Horsepower is expressed in units of ________.

foot-pounds per minute Correct. One horsepower is the power needed to move 550 pounds through one foot in one second or 33,000 pounds through one foot in one minute. It is measured in foot-pounds per minute or foot-pounds per second.

A single overhead camshaft (SOHC) design operates the valves _________ while a double overhead camshaft (DOHC) design operates the valves _______.

indirectly, directly Correct. A single overhead camshaft (SOHC) design operates the valves indirectly through components such as rocker arms while a double overhead camshaft (DOHC) design operates the valves directly.

The passage in the engine block and crankshaft through which lubricating oil flows is called the _____________.

oil gallery Correct. Lubricating oil flows through passages in the engine block and crankshaft called oil galleries.

The formula (π × R2 × Stroke × Number of Cylinders) provides the displacement or volume of the engine where R is the radius of the cylinder. R is _______ the value of the bore.

one-half Correct. Bore is the diameter of the cylinder and radius is 1/2 the diameter.

The coolant flow through the radiator is controlled by the _______________.

thermostat Correct. When the thermostat opens, the coolant is passed through the radiator where it releases heat to outside air.

A rotating force is called ________.

torque Correct. Torque is the rotating force that acts at the end of a lever. Engine torque is expressed as maximum torque at a particular speed (RPM) or a range of speeds.