Two-Stroke vs. Four-Stroke

How 2-Cycle and 4-Cycle Engines Differ

By  | Snow Blower Product Expert

Modern snowblowers are made with 4-stroke engines, but if you have a cherished snowblower from years ago, you've dealt with trying to get the perfect fuel mixture for a 2-stroke engine.

Many people grew up learning to eyeball the oil-gas ratio, but properly mixing gasoline and oil will prevent your snowblower from spitting out the dark clouds of smelly smoke that nobody enjoys.

 

What's the Difference Between Two-Stroke & Four-Stroke?

A "stroke" refers to how many stages (cylinder/crankshaft movements) a combustion engine needs to complete to finish a "power (working) stroke." 

Two-stroke (two-cycle) engines require you to mix the oil with the gas in exact amounts so the oil acts as a lubricant for the crankcase, while four-stroke engines take oil and gas separately.

In a 2-stroke engine, it takes one full revolution (2 stages) to complete 1 power stroke.

In a 4-stroke engine, it takes two revolutions (4 stages) to complete 1 power stroke.

 

How Do 4-Cycle Engines Work?

Four-stroke (four-cycle) engines are newer and have a separate compartment for oil, so you don't have to worry about mixing fuel. These engines are more fuel-efficient and environmentally friendly, while also giving you more torque when you need it. View the diagram below to understand how these engines work.

4-Cycle Engine Diagram

  1. Intake: a downward stroke draws in fuel

  2. Compression: an upward stroke expels the exhaust

  3. Combustion (Power): another downward stroke brings in more fuel and ignites it

  4. Exhaust: another upward stroke compresses and expels the fuel

 

How Do Two-Cycle Engines Work?

2-stroke engine combines the compression and ignition steps on its upstroke while combining the power and exhaust on the downstroke. Because there are fewer moving parts in this engine, easier maintenance is traded for less power and torque.

2-Cycle Engine Diagram

  1. Ignition/Compression: the piston moves up, draws fuel in and compresses it

  2. Combustion/Exhaust: as the fuel is ignited, the piston is forced down, expelling the exhaust

 

Which is Better 2-Cycle or 4-Cycle?

While there are benefits of using both 2-cycle and 4-cycle snowblowers, it comes down to convenience and efficiency; if you're tired of mixing oil and sniffing fumes, it may be time to upgrade to a newer 4-stroke model.

Industry-wide, manufacturers are making more powerful 4-cycle engines and phasing 2-cycle out in favor of more powerful, more efficient machines.  Some argue that 2-cycle engines have mostly run their courses, but either way, it seems it won't be long before they disappear completely.

 

 
 

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