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What is an Air-Cooled Engine?

An air-cooled engine relies on air flow to dissipate heat, eschewing the liquid coolant systems found in most cars. This simpler, lighter design enhances thermal efficiency and reduces maintenance. Often found in vintage vehicles and motorcycles, its distinct hum speaks to a legacy of engineering ingenuity. Ever wondered how this classic innovation shapes modern driving experiences? Join us to explore further.
Lori Kilchermann
Lori Kilchermann

An air-cooled engine uses cooling fins cast into its cylinder head to dissipate heat instead of using a liquid-filled radiator. By eliminating the radiator, an air-cooled engine is able to be used in applications in which space restraints prohibit installing a radiator. As the air-cooled engine builds heat, the cooling fins allow the wind and air to move the heat away from the engine much like a person blowing on a piece of food that is too hot to eat. Used in every type of vehicle from aircraft, tractors and sports cars to motorcycles and boats, the air-cooled engine has proven reliable as well as durable. In applications such as aircraft use, the air-cooled engine prevents the extreme cold found in high altitudes from causing freezing problems such as those that plague liquid-cooled aircraft engines.

Popular in motorcycles due to its reduced weight, the air-cooled engine is used on some of the most expensive motorcycles as well as the most affordable models. Though often criticized for the tremendous amount of heat passed along to the riders' legs when sitting still, an air-cooled engine still remains the popular choice for many custom-built motorcycles worldwide. Many manufacturers of touring style motorcycles have elected to supply liquid-cooled versions in top-end motorcycles. The American-based Harley-Davidson motorcycle company, however, continues to offer air-cooled engine configurations as the primary engine package.

Harley-Davidson offers an air-cooled engine.
Harley-Davidson offers an air-cooled engine.

Many pieces of equipment used in the construction trade use an air-cooled engine to provide the power. This enables the equipment to be operated in severe climates without fear of freezing or overheating. By eliminating the radiator, water pump and coolant, there is far less maintenance required to keep the equipment up and running. Most non-liquid cooled engines operate at reduced engine speed, which reduces some of the wear and tear of the engine's internal components as well. One of the most notable exceptions to this rule is the chainsaw, which operates at a very high rate of speed.

The Wright J-6-9 Whirlwind engines that were used on the Ford Trimotor are examples of air-cooled radial engines.
The Wright J-6-9 Whirlwind engines that were used on the Ford Trimotor are examples of air-cooled radial engines.

Air-cooled engines that operate at high engine speeds are often 2-stroke versions. This type of engine uses a gas and oil mixture in the fuel tank, and the oil helps to cool the engine. This type of configuration also eliminates a great amount of oil in the engine's crankcase. The oil retains engine heat and adds to the cooling difficulties in a 4-stroke engine. This is why many 4-stroke engines require an external engine oil cooler to aid in maintaining proper temperatures.

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Discussion Comments


One question that has been debated time and time again since the waning popularity of air cooled engines in cars like Beetles and Corvairs has been why we don't see those in modern vehicles. Why aren't air cooled engines still available in some automobiles?

There doesn't seem to be a clear answer to that.


These are rare in cars, but have been used in a few such as the original Volkswagen Beetle for a few reasons. First of all, they are much lighter than water cooled engines for obvious reasons -- fewer components and no liquid to weigh down the engine. Also, the comparatively simple design makes them fairly easy and cheap to repair.

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    • Harley-Davidson offers an air-cooled engine.
      By: Craig Hosterman
      Harley-Davidson offers an air-cooled engine.
    • The Wright J-6-9 Whirlwind engines that were used on the Ford Trimotor are examples of air-cooled radial engines.
      The Wright J-6-9 Whirlwind engines that were used on the Ford Trimotor are examples of air-cooled radial engines.