Do You Know How an Engine Works?


By: Dave Davis

7 Min Quiz

Image: Unsplash by Erik Mclean

About This Quiz

While you don't have to know how to build a clock to tell what time it is, it is helpful to know how your engine works before you jump into the car and take off. Do you have a clue what's going on under the hood when you press down on the gas pedal? This quiz is designed to test your knowledge of the machine that makes traveling from place to place in your daily commute easier and safe. 

Should you be able to tear down and rebuild a motor before you get a driver's license? Nah. If that was the case, the roads would be deserted except for a select few mechanical geniuses! Knowing the basics of how the internal combustion engine operates, however, can be extremely valuable. Not only will you be able to have an intelligent conversation with your mechanic when your car needs servicing, but you'll also be able to avoid some of the damage that can occur to an engine operated by a neglectful owner. While the modern engine is a wonder of mechanical science, it still needs some love every now and then! 

Are you the kind of owner who can show it that love? 

We bet you are, and you can prove you know more than the average motorist by scoring high on this quiz! You'll never need to field strip and clean your engine, but we think you know how to keep your motorized buddy happy and on the road. Prove us right by taking this quiz! Let's do this!

When you get your oil changed (or change it yourself), this part also needs to be replaced. Which of these parts fits that description?

The oil filter can hold about a quart of oil on its own, so when the vehicle's oil is changed, this part needs to be changed out as well; otherwise, a sizable amount of dirty oil will contaminate the nice, clean lubricant that was just put in.


What is the name of the part in the cylinder that moves up and down, transforming the energy of the fuel into motion?

The pistons travel up and down the cylinder shaft, driven by the internal combustion process. They are forced down the cylinder by the explosion, and then compress the fresh fuel/air mix as they return up toward the cylinder head.


The name might be a little misleading, but which of these devices moves coolant around your engine?

Although modern cars are much more likely to use antifreeze than water in the coolant system, the water pump is the device that keeps things moving. If the water pump — which can be either electrical or mechanical — goes out, your car is about to heat up in a bad way.


What structure does exhaust gas flow through when leaving the engine?

After the internal combustion process, the spent gases must be removed to make room for the fresh fuel/air mixture. These gases go through the exhaust valve(s) of the cylinder and then leave the engine by flowing through the exhaust manifold.


Which of these is the "brain" of the modern automobile?

The Engine Control Unit, or ECU (also known as the DME, DDE and by other names), is the computer that your car uses to maintain proper working order. This processor takes information from various sensors around the engine and the rest of the car to make decisions about fuel allocation and other factors.


Which of these structures connects the engine to the transmission in a manual transmission vehicle?

When you shift gears in a car with a manual transmission, you are using the clutch to disengage the engine from the transmission while you change which gear the transmission is using. This is a smooth process for experienced drivers. With drivers who are just learning to use the clutch, however, you're going to get jerked around a bit until they get the hang of it.


The distributor cap did its job for many, many years, but it was eventually replaced by which of these parts?

Each cylinder in your modern car has its own ignition coil, which sends the necessary electricity to each spark plug to ignite the fuel/air mix and drive the pistons. This job used to be accomplished by the distributor cap and points. Time, however, marches on.


Which of these devices keeps the camshaft and the crankshaft in sync?

The timing belt connects the camshaft and the crankshaft to keep the two elements in sync. The crankshaft rotates twice for every time the camshaft rotates, and they must work in harmony so that the valves open and close at the right moment in the four-stroke cycle.


In the internal combustion engine, which of these is the correct order of the combustion process?

The four-stroke internal combustion engine first takes in the fuel/air mix, then compresses it. The compressed mixture is then ignited, releasing its power and moving the piston. Finally, the exhaust gases are removed and the process starts again.


This device stores rotational energy for use by the engine — can you name it?

Since the internal combustion process is uneven, stored rotational energy can be a huge help in evening out the ride. In a car's engine, this is accomplished by the flywheel, which spins with the crankshaft and aids in keeping the spinning going at a more consistent rate.


When an engine has high torque, what does this mean?

Torque is a measure of turning power and is usually measured in foot-pounds (or Newton-meters). Just as horsepower is a measure of engine power, torque is a measure of how quickly the vehicle can accelerate.


Which of these parts took the place of the carburetor in modern cars?

In older vehicles, the carburetor was in charge of creating the fuel/air mixture necessary for the internal combustion process. In modern cars, this duty is filled by the fuel injectors, which keep the fuel and air separate until they enter the cylinder chamber, giving it a more consistent flow.


Which auxiliary motor does your car's engine need to get going?

The starter motor is an electric engine that gives the initial boost that causes the automobile's engine to turn over for the first time and get the internal combustion process started. Before they became a standard part of the car, drivers had to use a crank to get the engine started.


Which part turns the linear motion of the pistons into rotational force that can be used by the wheels?

Connected to the pistons by the hinged — and logically named — connecting rods, the crankshaft is rotated by the pistons' linear motion and transmits this motion to the transmission, which ultimately moves the wheels.


What scientific principle do radiators use to cool the engine?

The radiator operates by allowing hot engine coolant to flow through small tubes and come into contact with moving air (from the car being in motion and/or the radiator fan). The air cools the fluid, drawing away some of the engine's heat, and keeps the engine from overheating.


At what point in the internal combustion process does the Mass Air Flow sensor take its readings?

The Mass Air Flow sensor reads how much air is flowing into the engine at any given moment and helps the car's onboard computer determine how much fuel is needed to achieve the desired level of power. The computer will start throwing warning lights and the car will not run smoothly if this part gets contaminated or its electronics fail.


When you add headers to an engine, what system are you augmenting?

Exhaust headers are one of the most common aftermarket accessories used by people who want to get some extra pep out of their engine. They work by giving each cylinder its own exhaust system rather than using a common exhaust manifold. This helps to eliminate backpressure and ups the engine's horsepower and torque capabilities.


Where are freeze plugs usually located in a car?

Freeze plugs are usually found on the back, the side or underneath the engine block, and help to relieve pressure inside the block in freezing conditions. When water freezes and expands, the freeze plugs give the pressure a safe place to go.


Which of these directly drives the alternator as it provides electricity to the car?

The serpentine belt is connected to many components in your car's engine, including the alternator. By putting it in motion, the serpentine belt allows the alternator to generate electricity for the car's systems and makes sure the battery is properly charged. Older cars may have an alternator belt which just handles that part.


What is the function of the head gasket?

The head gasket is what separates the cylinder head from the engine block, allowing the two elements to work together and form a tight combustion chamber. Water, oil, fuel and exhaust gases also flow through the proper channels in the head gasket. When there's something wrong with this gasket, the engine quickly starts to display symptoms.


Your engine has these two types of valves. Can you name them?

The intake valves allow the fuel/air mixture to be injected into each cylinder for the internal combustion process, and then the exhaust valves release the spent gases to make room for the next cycle. Each cylinder, by the way, may have more than one of each valve.


If this part starts to fail, the entire car will start to feel the engine's vibrations. Which part are we talking about?

The engine and transmission are held in place in the car's frame by a series of mounts. These mounts are rubberized and, if they get worn and start to fail, the entire passenger compartment will start to feel the vibration of the engine, giving the riders an unwelcome massage.


How does the camshaft position sensor work to ensure the proper function of your engine?

The camshaft position sensor tells the car's computer when to release fuel to each cylinder by letting it know what position the camshaft is currently in. If this sensor starts to give bad readings, the spray of fuel will be incorrect and the engine will not run properly.


How many rings does each piston have in your car's engine?

The pistons in an automotive engine typically have three rings. The top two rings aid in compression, making a tight fit between the piston and the cylinder wall while the ring aids in controlling oil and dissipating heat generated in the combustion process.


The job of opening and closing valves in the operation of an engine falls to the ...

The camshaft, which rotates in time with the crankshaft, opens and shuts the valves going to the cylinders through the use of offset lobes (or cams). This keeps everything moving in the proper order throughout the internal combustion process.


How does the thermostat affect the temperature of the engine?

The thermostat in your car's engine is actually a valve that stays closed when the engine first starts and then opens when the engine is warm enough to need the flow of coolant to draw the heat away. If this part gets stuck, the engine can easily overheat.


It's on the dashboard of most cars, but what does the tachometer actually measure?

The tachometer is a gauge that measures how many times the crankshaft revolves in a minute (revolutions per minute, or RPM). At idle, the tachometer generally reads about 1,000 RPM for most cars.


True or false: The gap at the end of each spark plug needs to be precisely set.

When it comes to an internal combustion engine, timing is everything, and that includes the time it takes for a spark to travel between the electrodes of a spark plug to ignite the fuel/air mix in the cylinder. The gap at the end of each spark must be set to the exact distance specified by the manufacturer for the engine to run properly.


When an engine is referred to as a "Hemi," what does that actually describe?

The top of the combustion chamber of a Hemi engine are hemispherical (rather than flat), giving the engine its name. While hemi engines are more complex and more expensive, they can generate more power than a regular engine of the same size.


What is the function of the heater core?

The heater core is an ingenious bit of engineering, taking what would have otherwise been wasted heat and putting it to work to warm the passenger compartment and operate the defroster. It does this by taking some of the heat from the engine coolant and putting it to work.


How does a turbocharger add to the engines' power output?

A turbocharger is a turbine that increases the engine's power output by forcing compressed air into the cylinder — more air means more fuel can be introduced, which leads to bigger explosions and more power.


When you want to go faster, you press on the accelerator pedal. What actually happens when you do this?

The accelerator pedal actually controls the engine's throttle (the mechanism that controls how much air is entering the engine). When you allow more air in, more fuel is added to the mix, and the vehicle goes faster. The "gas" pedal is actually the "air" pedal.


Which of these is NOT an engine cylinder configuration?

The most common engine configurations for automobiles are inline, or I, meaning the cylinders are in a straight line, and V (V6, V8), meaning the engine has two banks of cylinders that resemble the letter "V." Less common, but still in existence, are the "W" engines, which have three banks of cylinders that resemble that letter.


Where is the oxygen sensor in the modern car mounted?

The car's oxygen sensors help with the smooth operation of the car's engine, even though they are located near the catalytic converter. These sensors detect how much unused oxygen is present in the engine's exhaust and help the vehicle's computer better calibrate how much fuel is needed for the fuel/air mix.


Which of these parts do sports cars and heavy-duty trucks often have in common?

When an engine is going to have extra strain on it — be it pulling or carrying heavy loads or being required to go really fast — oil coolers help take some of the pressure off the motor and keep it in good working order. There are also transmission coolers designed for the same purpose.


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