2-Stroke vs 4-Stroke Engines: What's the Difference?

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2-Stroke vs 4-Stroke Engines: What's the Difference?
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About This Quiz

What's more powerful - a two-stroke engine or a four-stroke engine? Think you know? Prove your engine expertise by acing this quiz!

So, let's start with the basics. All engines have pistons that perform a specific number of strokes to complete a power cycle. Four-stroke engines complete the cycle with four strokes (two up-and-down motions) of the piston, resulting in two revolutions of the crankshaft. Two-stroke engines complete the cycle with two strokes of the piston (one up-and-down motion), resulting in one revolution of the crankshaft. Two-stroke engines get the job done with fewer parts and are therefore lighter, which in turn makes the engine more efficient.

Because two-stroke engines are lighter, they are perfect for smaller gasoline engines, such as those used in lawnmowers, chainsaws and even model airplanes and motorcycles. But even when the weight factor does not come into play, two-stroke engines are more efficient, making them ideal for many applications. Even if you aren't particularly familiar with the difference between a two-stroke engine and a four-stroke engine, you'll know that you're operating a two-stroke engine when you are required to mix the fuel and the oil together.

So, you think you know enough about engines to ace this quiz? Let's get started.

Oil change
Avalon_Studio
Two-stroke engine oil is also known as …
Two-cycle oil
Two-piston oil
Two-inlet oil
Correct Answer
Wrong Answer

Two-cycle oil is used in many small engines, from boat motors to chainsaws.

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Modern Car Engine
kenneth-cheung
Compared to four-stroke engines, two-stroke engines tend to have what?
Longer lives
A good power-to-weight ratio
Better functionality
Correct Answer
Wrong Answer

They're often used in small power tools and light vehicles because of their excellent power-to-weight ratio.

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car key in ignition lock
deepblue4you
What kind of ignition do most two-cycle engines use?
Spark ignition
Compression ignition
Neither
Correct Answer
Wrong Answer

Gasoline ignition is especially common in the smallest two-stroke engines.

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car service
Hirurg
True or false: Two-stroke engines typically don't last as long as four-stroke engines.
True
False
Correct Answer
Wrong Answer

Their inefficient oiling methods mean less effective lubrication shorter engine life.

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Car mechanic replacing and pouring fresh oil into engine at maintenance repair service station
Prapass Pulsub
Compared to lubricating oil, two-cycle oil has less …
Mercury
Carbon dioxide
Ash
Correct Answer
Wrong Answer

Less ash makes burning the oil a bit cleaner.

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car service
mladenbalinovac
True or false: Compared to four-stroke engines, two-stroke engines have a shorter service life.
True
False
Correct Answer
Wrong Answer

To maintain their working life, staying on top of lubrication is especially important in two-stroke engines.

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Repair man working in garage on repair
eclipse_images
When compared to four-stroke engines, how many parts do two-stroke engines contain?
Fewer parts
More parts
The same number of parts
Correct Answer
Wrong Answer

The lower number of parts in a two-stroke engine is the primary reason they tend to be lighter.

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car spark plugs on engine
Jorge Villalba
How many times does the spark plug fire for each revolution of the crankshaft in a two-stroke engine?
Three times
Two times
One time
Correct Answer
Wrong Answer

It only fires once per revolution. This trait helps two-stroke engines produce more power, by weight, than four-stroke engines.

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Auto mechanic examining overheated car in a workshop
skynesher
What color is the smoke emitted from many small two-stroke engines?
Blue/gray
Brown
White
Correct Answer
Wrong Answer

It gets its blue tint from the oil that's blended into the fuel.

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Traffic jam
Jung Getty
True or false: You usually get more miles per gallon on a two-stroke engine than on a four-stroke engine.
True
False
Correct Answer
Wrong Answer

At smaller sizes, two-stroke engines aren't really fuel efficient.

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boat's outboard motor and propellers
gaspr13
Why are two-stroke outboard engines (for boats) NOT environmentally friendly?
Oil leakage
Coolant leakages
Friction problems mean higher emissions
Correct Answer
Wrong Answer

These engines can leave clouds of smoke and trails of oil in the water.

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Car salesman showing engine to customers
Photo_Concepts
What is a primary inovation of the new two-stroke engine that Honda unveiled in 2015?
It uses extra cylinders.
It uses direct fuel injection.
It has a new ignition technology.
Correct Answer
Wrong Answer

The point of the direct fuel injection is to reduce the amount of unburned fuel in the emissions, making them run cleaner.

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Powerful car engine
Arctic-Images
What is the name for the upward stroke of a two-stroke engine?
Exhaust
Compression
Combustion
Correct Answer
Wrong Answer

The upward stroke is the compression stroke, and the downward stroke is called the power stroke.

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Motorcycle engine close-up detail background
chain45154
What characteristic is typical of a two-stroke motorcycle's power band?
It is very narrow.
It is very wide.
It is the same as any other motorcycle.
Correct Answer
Wrong Answer

The range of RPMs that offer peak power on these bikes, known as the power band, occurs in a very limited range.

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Auto Repair Garage with Mechanic, Torque Crankshaft Main Bearings
patrickheagney
Dugald Clerk's two-stroke engine was the first to do what during every revolution of the crankshaft?
Self-oil using a discrete oil tank
Self-correct for vibration from the pistons
Combine compression with ignition
Correct Answer
Wrong Answer

It combined compression with ignition during each revolution. Clerk succeeded where other inventors had already failed.

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work on car engine
Jose Luis Pelaez Inc
What is another name for the oil/gas mixture in a two-stroke engine?
Kerosene
Petroil
Gas
Correct Answer
Wrong Answer

Petroil, or two-stroke oil mixed with gasoline, makes the total-loss oiling system work.

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Close-up of muscle car engine compartment
AM-C
What is a typical compression ratio for a small four-stroke engine?
12-to-1
16-to-1
20-to-1
Correct Answer
Wrong Answer

The typical compression ratio is 12-to-1. Higher compression ratios generally mean more power.

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Sports car exhaust
Marin Tomas
In a two-stroke engine, at the start of a new stroke, both the inlet and exhaust ports are …
Open
Closed
Partially closed
Correct Answer
Wrong Answer

They are both open. Air pressure differences cause a fresh fuel/air mix to move into the combustion chamber.

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Ship's engine room
cunfek
Compared to four-stroke engines, how efficient are the enormous two-stroke diesel engines used on ships?
They are far less efficient.
They are far more efficient.
They are about the same.
Correct Answer
Wrong Answer

It seems bigger really is better when it comes to the efficiency of two-stroke engines.

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Engine crankshaft
schlol
How many revolutions does the crankshaft make during a power cycle in a two-stroke engine?
Six
Four
One
Correct Answer
Wrong Answer

The crankshaft, which converts the pistons' up-and-down motions into rotation, makes one complete turn each power cycle.

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US patent application
Don Farrall
What year was the first two-stroke engine (with in-cylinder compression) patented?
1781
1881
1913
Correct Answer
Wrong Answer

Dugald Clerk invented it in Scotland and patented his creation in England in 1881.

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Mechanic working under car in car dealership workshop holding torch
Monty Rakusen
What's an advantage of a rotary valve?
It makes asymmetrical engine timing possible.
It lowers noise levels.
It improves lubrication.
Correct Answer
Wrong Answer

Asymmetrical engine timing often results in better power output.

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Biker on adventure motorcycle ride
Henn Photography
Who created the first practical two-stroke motorcycles?
Wilhelm Maybach
Sylvester Roper
Alfred Scott
Correct Answer
Wrong Answer

Scott, who also had about 50 other patents to his name, founded the Scott Motorcycle Company in 1908.

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Mechanical engineer use computer check and programming to tune car after repair in the service shop
Cravetiger
How many strokes do two-cycle engines require to complete a power cycle?
Two
Four
One
Correct Answer
Wrong Answer

Two up-and-down motions make up the stroke (and the power cycle).

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nozzle fuel for fill oil into car tank at pump gas and oil station with technology icons concept design
Busakorn Pongparnit
For small two-stroke engines, approximately how many ounces of two-stroke oil do you need per gallon of gas?
2 fluid ounces
4 fluid ounces
8 fluid ounces
Correct Answer
Wrong Answer

You need 4 ounces of oil per gallon of gas — and it can be pricey, too.

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Car mechanic is changing engine oil
choja
In small two-cycle engines, where does the oil originate?
Oil sump
Carburetor
Neither
Correct Answer
Wrong Answer

The oil originates in the carburetor and, from there, is mixed directly into the fuel.

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Washing the Car and inspect engine compartment for trouble
primeimages
What is the most common type of inlet port on smaller two-stroke engines?
Rotary
Reed
Piston-controlled
Correct Answer
Wrong Answer

In this configuration, the piston covers and uncovers the ports as it travels up and down the cylinder. The 1970s saw significant improvements in piston-controlled inlet ports.

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Engine cylinder
Marin Tomas
What is a typical compression ratio for a small two-stroke engine?
2-to-1
6-to-1
10-to-1
Correct Answer
Wrong Answer

The 6-1 compression ratio, which means the volume of the mixture is compressed by the piston in the cylinder to one-sixth of its original, is fairly low for small engines.

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Check the oil in Car Engine
gece33
How do the lubrication systems on large two-stroke engines work as compared to large four-stroke engines?
They are very similar.
They are completely different.
As with smaller two-stroke engines, you're required to add oil to the fuel.
Correct Answer
Wrong Answer

The oil-fuel mixing process is mainly for smaller and cheaper two-stroke engines.

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Modern powerful car engine
Cravetiger
Compared to four-stroke engines, what are the characteristics of emissions from small two-stroke engines?
They are the same.
Two-stroke engines are a little cleaner.
Two-stroke engines emit dirtier exhaust.
Correct Answer
Wrong Answer

The emissions are higher in large part due to the oil that's mixed with the gasoline.

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