The Engine Quiz!

It’s under the hood of every car, truck and SUV (unless the vehicle is electric), but how many people really know how an engine works? Do you know a spark plug from a fuel injector? Test your auto smarts in our engine quiz!

Have you ever opened the hood of your car and wondered what was going on in there? A car engine can look like a big confusing jumble of metal, tubes and wires to the uninitiated. You might want to know what’s going on simply out of curiosity. Or perhaps you are buying a new car, and you hear things like “3.0 liter V-6” and “dual overhead cams” and “tuned port fuel injection.” What does all ­of that mean? The ­principle behind any reciprocating internal combustion engine: If you put a tiny amount of high-energy fuel (like gasoline) in a small, enclosed space and ignite it, an incredible amount of energy is released in the form of expanding gas. You can use that energy to propel a potato 500 feet. In this case, the energy is translated into potato motion. You can also use it for more interesting purposes. For example, if you can create a cycle that allows you to set off explosions like this hundreds of times per minute, and if you can harness that energy in a useful way, what you have is the core of a car engine!

Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion. The four-stroke approach is also known as the Otto cycle, in honor of Nikolaus Otto, who invented it in 1867. The four strokes are illustrated in Figure 1. They are: The core of the engine is the cylinder, with the piston moving up and down inside the cylinder. The engine described above has one cylinder. That is typical of most lawn mowers, but most cars have more than one cylinder (four, six and eight cylinders are common). In a multi-cylinder engine, the cylinders usually are arranged in one of three ways: inline, V or flat (also known as horizontally opposed or boxer), as shown in the following figures. Different configurations have different advantages and disadvantages in terms of smoothness, manufacturing cost and shape characteristics. These advantages and disadvantages make them more suitable for certain vehicles.

What are the two main components of the engine cooling system in most cars?
air intake and turbocharger
battery and fan
radiator and water pump

Correct!

Wrong!

What happens if your car leaks or burns off all of its oil?
It’ll start an oil fire.
The engine will seize.
It’ll cause oil poisoning.

Correct!

Wrong!

What are the three common ways to deliver fuel to an engine?
Carburetion, hybridization, electrical charging
fuel injection, infusion, circulation
carburetion, port fuel injection, direct fuel injection

Correct!

Wrong!

What is an octane rating?
a way to tell how fast a car can go
a way to tell how much the fuel can be compressed
a way to tell how much the engine will wear out

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Wrong!

What is an engine’s redline?
how much nitrous oxide you can use
an engine’s maximum rpms
an equation that determines when the turbo kicks in

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Wrong!

A car engine's job is to:
convert fuel into heat
convert fuel into motion
convert fuel into exhaust

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Wrong!

A car uses a four-stroke engine. The four strokes are:
intake, compression, combustion and exhaust
injection, rotation, combustion and exhaust
injection, carburetion, rotation and exhaust

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Wrong!

A crankshaft's job in an engine is to:
deliver fuel to the cylinders
change linear motion into rotational motion
keep cylinder heads in place

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Wrong!

A timing belt or timing chain links these two components together so that the valves are in sync with the pistons:
the flywheel to the camshaft
the crankshaft to the camshaft
the cylinder head to the camshaft

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Wrong!

There are three basic failures that can happen in an engine: bad fuel mix, lack of compression and:
lack of exhaust
lack of water
lack of spark

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Wrong!

In a car engine's cylinder, valves let fuel in and exhaust out. The ______ moves these valves.
camshaft
timing belt
distributor

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Wrong!

A turbocharger is:
a set of gears that makes the wheels turn faster
a turbine that compresses the air traveling into the engine
an injector that delivers fuel to the engine faster

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Wrong!

When you turn the key to a car, the starter motor:
sends electricity to the spark plugs, starting ignition
sends electricity to the fuel pump, forcing the car to start
spins the engine a few revolutions, starting the combustion process

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Wrong!

Modern cars use internal combustion engines, but some early models used external combustion engines. What is one example of an external combustion engine?
steam engine
firecracker engine
hydroponic engine

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Wrong!

Why don’t we use steam engines for cars anymore?
They set off too many smoke alarms.
They smelled too bad.
They aren’t as efficient.

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Wrong!

What are the three common ways to arrange an engine’s cylinders?
V-6, V-8, HEMI
inline, V, flat
inline, flat, rotary

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Wrong!

What might happen if water gets into your gas tank?
It’ll make it hard for the engine to burn the fuel.
It’ll help the car get better gas mileage.
It’ll make the engine blow up.

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Wrong!

Which of these cars features a popular example of an air-cooled engine?
the Tesla Model S
the Volkswagen Beetle
the Ford Model T

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Wrong!

Which of the following commonly uses air-cooled engines?
motorcycles
hybrid cars
Oscar Mayer Wienermobiles

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Wrong!

What is the steam engine’s main advantage?
It’s easy to fix.
It can use anything as fuel.
Steam pollutes less.

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Wrong!

What are two of the main advantages to a 4-cylinder engine?
It’s efficient and compact.
It’s faster and makes less exhaust.
It’s cheaper and can use watered-down gas.

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Wrong!

What are two other terms for engine knock?
banging and clunking
clicking and clacking
pinging and detonation

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Wrong!

When a car's engine is running, power to operate the radio, CD player, headlights and windshield wipers comes from the:
alternator
battery
spark plugs

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Wrong!

Name one of the causes of engine knock.
the wrong spark plugs
driving too fast
being low on oil

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Wrong!

What are the three functions of engine oil?
lubrication, cooling, cleaning
lubrication, getting rid of exhaust smell, making gas more powerful
cooling, cleaning, making more money for Jiffy Lube

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Wrong!

What’s another name for the four-stroke engine cycle?
Otto cycle
Tesla cycle
compression cycle

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Wrong!

Why does engine oil need to be changed?
The engine’s movement compresses too much oil.
It gets too dirty to work.
The oil evaporates in the summer.

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Wrong!

A device that works on the same principle as a car engine is:
a nuclear submarine
a giant robot
a spud gun

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Wrong!

What does ECM stand for, and what does it do?
engine control module, which is the engine’s computer
engine catheter manager, which controls the oil coming out of the engine
European custom mechanical, which helps race car owners keep track of their modifications

Correct!

Wrong!

Why does a diesel engine get better mileage than a gasoline engine?
because of coal rolling
because it contains more energy
Actually, it doesn’t.

Correct!

Wrong!

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The Engine Quiz!

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So you go out one morning and your engine will turn over but it won’t start… What could be wrong? Now that you know how an engine works, you can understand the basic things that can keep an engine from running. Three fundamental things can happen: a bad fuel mix, lack of compression or lack of spark. Beyond that, thousands of minor things can create problems, but these are the “big three.” Based on the simple engine we have been discussing, here is a quick rundown on how these problems affect your engine: Bad fuel mix – A bad fuel mix can occur in several ways: Most engine subsystems can be implemented using different technologies, and better technologies can improve the performance of the engine. Let’s look at all of the different subsystems used in modern engines, beginning with the valve train.

The valve train consists of the valves and a mechanism that opens and closes them. The opening and closing system is called a camshaft. The camshaft has lobes on it that move the valves up and down. The cooling system in most cars consists of the radiator and water pump. Water circulates through passages around the cylinders and then travels through the radiator to cool it off. In a few cars (most notably Volkswagen Beetles), as well as most motorcycles and lawn mowers, the engine is air-cooled instead (You can tell an air-cooled engine by the fins adorning the outside of each cylinder to help dissipate heat.). Air-cooling makes the engine lighter but hotter, generally decreasing engine life and overall performance. See How Car Cooling Systems Work for details. So now you know how and why your engine stays cool.

But why is air circulation so important? Most cars are normally aspirated, which means that air flows through an air filter and directly into the cylinders. High-performance engines are either turbocharged or supercharged, which means that air coming into the engine is first pressurized (so that more air/fuel mixture can be squeezed into each cylinder) to increase performance. The amount of pressurization is called boost. A turbocharger uses a small turbine attached to the exhaust pipe to spin a compressing turbine in the incoming air stream. A supercharger is attached directly to the engine to spin the compressor. When it comes to day-to-day car maintenance, your first concern is probably the amount of gas in your car. How does the gas that you put in power the cylinders? The engine’s fuel system pumps gas from the gas tank and mixes it with air so that the proper air/fuel mixture can flow into the cylinders. Fuel is delivered in three common ways: carburetion, port fuel injection and direct fuel injection.

Using all of this information, you can begin to see that there are lots of different ways to make an engine perform better. Car manufacturers are constantly playing with all of the following variables to make an engine more powerful and/or more fuel efficient. Increase displacement – More displacement means more power because you can burn more gas during each revolution of the engine. You can increase displacement by making the cylinders bigger or by adding more cylinders. Twelve cylinders seems to be the practical limit.

Here is a set of engine-related questions from readers and their answers:

What is the difference between a gasoline engine and a diesel engine?
In a diesel engine, there is no spark plug. Instead, diesel fuel is injected into the cylinder, and the heat and pressure of the compression stroke cause the fuel to ignite. Diesel fuel has a higher energy density than gasoline, so a diesel engine gets better mileage.

What is the difference between a two-stroke and a four-stroke engine?
Most chain saws and boat motors use two-stroke engines. A two-stroke engine has no moving valves, and the spark plug fires each time the piston hits the top of its cycle. A hole in the lower part of the cylinder wall lets in gas and air. As the piston moves up it is compressed, the spark plug ignites combustion, and exhaust exits through another hole in the cylinder. You have to mix oil into the gas in a two-stroke engine because the holes in the cylinder wall prevent the use of rings to seal the combustion chamber. Generally, a two-stroke engine produces a lot of power for its size because there are twice as many combustion cycles occurring per rotation. However, a two-stroke engine uses more gasoline and burns lots of oil, so it is far more polluting.

You mentioned steam engines in this article — are there any advantages to steam engines and other external combustion engines?
The main advantage of a steam engine is that you can use anything that burns as the fuel. For example, a steam engine can use coal, newspaper or wood for the fuel, while an internal combustion engine needs pure, high-quality liquid or gaseous fuel.

Are there any other cycles besides the Otto cycle used in car engines?
The two-stroke engine cycle is different, as is the diesel cycle described above. The engine in the Mazda Millenia uses a modification of the Otto cycle called the Miller cycle. Gas turbine engines use the Brayton cycle. Wankel rotary engines use the Otto cycle, but they do it in a very different way than four-stroke piston engines.

Why have eight cylinders in an engine? Why not have one big cylinder of the same displacement of the eight cylinders instead?
There are a couple of reasons why a big 4.0-liter engine has eight half-liter cylinders rather than one big 4-liter cylinder. The main reason is smoothness. A V-8 engine is much smoother because it has eight evenly spaced explosions instead of one big explosion. Another reason is starting torque. When you start a V-8 engine, you are only driving two cylinders (1 liter) through their compression strokes, but with one big cylinder you would have to compress 4 liters instead.