What Do You Know About Car Engines?


By: J. Reinoehl

7 Min Quiz

Image: Jose Luis Pelaez Inc/DigitalVision/Getty Images

About This Quiz

Whether you’re a factory-trained, professional auto technician or a shade tree mechanic who likes to tinker with old cars, you have to know an awful lot about engines to maintain and repair them properly. And you really have to know your stuff if you’re into modifying engines for more performance. 

Well, if you know your wrist pins from your crank pins, this quiz is for you. If you’re the one that friends and relatives call for help every time their cars' engines make funny noises, you ought to breeze through these 35 questions quicker than a Dodge Hemi V8 goes through a gallon of gas. 

Now, even though piston engines work pretty much the same as they did 100 years ago, much has changed over the decades. Some young car enthusiasts today have never had the satisfaction or frustration of working rebuilding a carburetor or fiddling with a distributor to get the ignition timing just right. Meanwhile, there some “old school” enthusiasts still shake in their shoes at the sight of a fuel injection system or an engine control unit. And then, there are those who can work on any engine ever made and make it sing. 

Which one are you? Take this quiz and find out!

What is the purpose of a torque wrench?

A torque wrench is used to tighten bolts to a specific tension setting. A gauge or digital readout on the wrench indicates when correct torque is applied. Using a torque wrench is critical when tightening bolts on engine parts, such as connecting rod bolts, main bearing cap bolts, and cylinder head bolts, among others.


Cars with fuel injection no longer need which device?

If you’re old enough to remember carburetors in passenger cars, you’ve been driving a long time. While fuel injection had been used on a few cars since the 1950s, the advent of computerized control in the 1980s made it more common. A far more precise method for supplying fuel to the cylinders, fuel injection proved invaluable for increasing power while reducing emissions and improving fuel economy.


What is one difference between gasoline and diesel engines?

Gasoline engines compress the air/fuel mixture, and a spark plug ignites it. In a diesel engine, high compression alone ignites the mixture, but diesel engines also use glow plugs to help start the process on very cold days.


Thick white smoke coming out the exhaust usually means what?

A car leaving a trail of white smoke from the tailpipe is a telltale sign that either the cylinder block has cracked or a head gasket has failed. A cracked block can also leak oil.


What should you do if your car begins to overheat?

An engine that is overheating can be damaged quickly. After safety pulling off the road, stop the engine and let it cool before opening the hood to check anything. Opening the hood right away can unleash a cloud of scalding hot steam right in your face.


What part opens and closes engine valves?

A shaft with oblong-shaped lobes, the camshaft operates “followers” that push intake and exhaust valves open at precise intervals. Pressure from valve springs allows the valves to close.


The connecting rod does what?

The connecting rod connects to the piston to the crankshaft, converting the pistons’ vertical motion in the cylinders (as the combustion cycle pushes the piston downward) into rotational motion that turns the crankshaft.


Which component did Cadillac introduce so the driver no longer had to turn a crank?

Before Cadillac introduced the electric starter in 1912, car owners had to manually crank the engine to initiate the combustion process. It was difficult and dangerous to do, and could even break a person’s arm.


If the engine is overheating, which of the following is a likely reason?

It’s much less common for a modern car engine to overheat than it was in the past, but when it happens, checking the thermostat (when the engine cools down) is usually the second thing to do after first determining if the radiator or a hose is leaking coolant.


Which part of the engine do you need a harmonic balancer tool to install and remove properly?

Before removing a crankshaft from an engine, you use a harmonic balancer remover to remove the harmonic balancer.) Don’t you just love that its name is exactly what it does?) This is the part that connects the crankshaft to the drive belt pulleys and also helps reduce vibration.


What is the most likely reason you would notice spark plugs coated in oil when you are changing them?

This is more likely to be a problem in an old, worn engine. Oil that leaks past piston rings or valve stems gets makes its way to the combustion chamber and “fouls” the spark plug. The result could be misfiring, or not firing at all.


What is the purpose of a fuel injector?

A fuel injector does just what its name suggests, injecting fuel into the engine to burn. First, it atomizes the fuel, turning it into a fine spray. In many modern car engines, “direct injection” puts the fuel right into the combustion chamber. Other kinds of fuel injection have been used to inject it further upstream, either into the intake manifold or the cylinder ports.


When the thermostat is hot, what does it do?

After you start your car’s engine, its internal temperature will begin to increase as a result of the combustion cycles. When a pre-set temperature is reached, the thermostat opens to allow engine coolant to flow between the engine and radiator. A “stuck” thermostat can cause the engine to overheat.


What does DOHC stand for?

In an inline four- or six-cylinder engine, “DOHC” means double overhead-cam, which means the engine has two camshafts, one to operate the intake valves, and the other to work the exhaust valves. In a V-type engine, DOHC means two camshafts per cylinder bank for a total of four.


In what way can you "tune" the exhaust system to increase engine power?

Headers, something that once only hotrodders and racers used, work more efficiently at extracting exhaust gases than traditional exhaust manifolds. That’s because headers use individual pipes for each cylinder, rather than combining pipes for two or more cylinders. On some modern engines, exhaust manifolds are designed to work more like headers.


An OHV engine has a camshaft located where?

“OHV” stands for overhead-valve. This means the camshaft is located in the cylinder block, above the crankshaft, rather than in the cylinder head. In such a setup, the camshaft operates long pushrods that reach up to rocker arms to operate the valves in the cylinder heads. The Chevrolet and Bentley V8s still OHV engine designs, so you know they can still make a lot of power.


What is the order of a four-stroke engine cycle?

In a “four-stroke” engine, which is all passenger car and most motorcycle engines today, (1) the intake stroke moves the piston downward, pulling the air-fuel mixture through the intake valves into the cylinder; (2) the compression stroke moves the piston upward to compress the mixture; (3) the spark plug ignites the mixture, creating the power stroke that pushes the piston downward, and (4) the piston moves back upward in the cylinder, pushing the combustion gases out through the exhaust valves.


Which of the following tools would be used to clean debris from threaded holes?

When working on or rebuilding an engine, you would use something called a “chaser” tap to clean or re-form existing threads. A “cutter” tap is used to create new threads. Both tools must be used very carefully.


What attaches the piston head to the connecting rod?

The wrist pin (gudgeon pin if you live in the U.K.) is a kind of bearing that allows the connecting rod to pivot as the piston moves up and down.


Which of the following is not an electric car?

Okay, this is a bit of trick question, since it’s not about engines, really. Honda does offer an electric vehicle, called the Clarity Electric (with a pitifully short battery range), but there’s no electric Civic. The Toyota Mirai is a fuel cell EV, meaning it generates its own electricity onboard through a reaction between hydrogen and oxygen.


What is the purpose of a catalytic converter?

Catalytic converters have been used to control automobile exhaust pollution since the mid-1970s. Part of the exhaust system, today’s “three-way” catalytic converters use precious metals like platinum and palladium to convert harmful carbon monoxide, unburned hydrocarbons, and smog-causing nitrogen oxides into carbon dioxide, water, and harmless oxygen and nitrogen. If you see water dripping out of your car’s exhaust pipe, that’s the catalytic converter at work.


If blue smoke is coming out of the exhaust pipes, which of the following is most likely the cause?

Blue smoke from a car’s exhaust pipe is a sure sign that oil is slipping past worn or damaged piston rings or valve seals and into the combustion chamber.


Which are the two most common engine configurations in cars today?

Inline and V-type engines have long been the most common in cars. Examples today include inline-four, inline-six, V6, V8, and V12. Porsche sports cars (but not SUVs and sedans) use a “flat” or horizontally opposed cylinder layout, as do Subarus. Bentley and Bugatti use an oddball “W” configuration, which is based on the Volkswagen narrow-angle VR4 and VR6 engine design.


The Wankel engine is unique because of what?

Instead of converting reciprocating motion into rotational motion with pistons, connecting rods and a crankshaft, a Wankel (a.k.a. “rotary”) engine uses elliptical rotors inside a small, barrel-shaped engine case. A Wankel has no camshafts, and instead of poppet valves operated by camshafts, there are stationary intake and exhaust ports that are alternately exposed and covered as the rotors spin on a shaft. It’s a far simpler and lighter design than a piston engine, but it tends to use more fuel and also burn oil.


What is a ring compressor used for?

Here’s another tool named for its single job. You use a ring compressor to hold and compress the piston rings as you install the piston into the cylinder bore.


Which of the following is NOT an advantage of multi-valve engines?

A piston engine pulls air in to be oxidized with fuel through combustion, so it makes sense that more valves let in more air. With four valves per cylinder, the two intake and two exhaust valves are individually smaller than the valves in a two-valve design, but together they have more surface area. Their smaller size has other benefits, as well. Compared to a two-valve engine, however, production cost is usually higher.


A four-stroke engine with which of the following number of valves would not be considered a multi-valve engine?

Any four-stroke engine must have at least two valves, one intake and one exhaust. Most modern car engines use four valves per cylinder, so this was called “multi-valve.” In the past, three- and even five-valve-per-cylinder engines have been used.


The starter starts the engine using which principle?

A car’s starter is a small electric motor that turns the flywheel, therefore the crankshaft, to initiate the combustion process. An electric motor uses coil of wires around an electromagnet and turns when fed current.


Which of the following is an advantage of poppet valves over sleeve valves?

Poppet valves, as opposed to sleeve valves last used in some cars in the 1930s, have almost no oil leakage. The name “poppet” is derived from “puppet,” a vague visual description for how the valves appear to operate.


Engine cylinders fire in the correct order because of what?

Don’t look for a distributor in a modern automobile engine. Beginning in the late 1980s, computers began taking over the task of distributing the electric current that fires the spark plugs. The computer activates individual coils for each cylinder to provide the current at just the right intervals.


Which of the following is NOT a function of the correct firing order in an engine?

The optimal firing order depends on specific engine configurations, but in all cases it is chosen to yield an optimal combination of power production from the combustion cycles and minimal vibration.


What is the usual firing order for an inline 4-cylinder engine?

1-3-4-2 is the usual firing order for an inline four, although 1-2-4-3 is another acceptable but less frequently used order.


What is the purpose of a flywheel?

A flywheel is a heavy disc attached to the end of the engine’s crankshaft. As it turns with the crankshaft, its rotation essentially maintains the engine’s momentum and smooths out the power pulses as the individual cylinders fire.


What are some disadvantages gasoline engines have compared to diesel engines?

Diesel engines can be more fuel-efficient than gasoline engines, and they produce less carbon monoxide. However, these benefits are usually outweighed by the diesel producing more of other pollutants (including particulate matter), making more noise, weighing more and costing more to produce. Also, emission controls for diesels are more complex and more expensive than for gasoline engines. Just ask Volkswagen.


What is the purpose of honing?

When rebuilding an engine, you “hone” the cylinders, using a special tool to put a fine crosshatch pattern in the cylinder wall to help it retain lubricating oil across its surface area when the engine is operating.


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