The Two-Stroke Engines Quiz


By: Staff

5 Min Quiz

Image: refer to hsw

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 of the piston, resulting in two revolutions of the crankshaft. Two-stroke engines complete the cycle with two strokes of the piston, 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 together the fuel and the oil.

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

Compared to lubricating oil, two-cycle oil has less …

Less ash makes burning the oil a little bit cleaner.


How many strokes do these engines require to complete a power cycle?

Hence the name.


How many revolutions does the crankshaft make during a power cycle in a two-stroke engine?

The crankshaft makes one complete turn.


What color is the smoke emitted from many small two-stroke engines?

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


What year was the first two-stroke engine (with in-cylinder compression) patented?

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


Clerk's engine was the first to do what during every revolution of the crankshaft?

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


Compared to four-stroke engines, two-stroke engines tend to have what?

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


In a two-stroke engine, at the start of a new stroke, both the inlet and exhaust ports are …

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


Who created the first practical two-stroke motorcycles?

Scott also had about 50 other patents to his name.


What is another name for the oil/gas mixture in a two-stroke engine?

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


When compared to four-stroke engines, how many parts do two-stroke engines contain?

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


What is a typical compression ratio for a small two-stroke engine?

The 6-1 ratio is fairly low for small engines.


What is a typical compression ratio for a small four-stroke engine?

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


How many times does the spark plug fire for each revolution of the crankshaft in a two-stroke engine?

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


What kind of ignition do most two-cycle engines use?

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


True or false: Compared to four-stroke engines, two-stroke engines have a shorter service life.

Staying on top of lubrication is especially important in two-stroke engines.


What's an advantage of a rotary valve?

Asymmetrical engine timing often results in better power output.


Compared to four-stroke engines, what are the characteristics of emissions from small two-stroke engines?

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


Two-stroke engine oil is also known as …

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


What is a primary trait of the new two-stroke engine that Honda unveiled in 2015?

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


What is the most common type of inlet port on smaller two-stroke engines?

The 1970s saw significant improvements in piston-controlled inlet ports.


For small two-stroke engines, how many ounces of two-stroke oil do you need per gallon (4 liters) of gas?

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


How do the lubrication systems on large two-stroke engines work as compared to large four-stroke engines?

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


True or false: Two-stroke engines typically don't last as long as four-stroke engines

Their inefficient oiling methods mean less effective lubrication shorter engine life


What is the name for the upward stroke of a two-stroke engine?

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


Why are two-stroke outboard engines (for boats) NOT environmentally friendly?

They leave clouds of smoke and trails of oil in the water.


In a small two-cycle engines, where does the oil originate?

The oil originates in the carburetor. It is mixed directly into the fuel.


True or false: You usually get more miles per gallon on a two-stroke engine than on a four-stroke engine.

Two-stroke engines aren't really fuel efficient.


Compared to four-stroke engines, how efficient are the enormous two-stroke diesel engines used on ships?

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


What characteristic is typical of a two-stroke motorcycle's power band?

Peak power on these bikes occurs in a very limited range.


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