Well. With the wind on the head of a 2CV it is true that you now have to plan some extra travel time. Such a 2CV has its limitations. But Volkswagen made Beetles, Porsche 911s, Tatra air-cooled V8s, and the Chevrolet Corvairs had air-cooled six-cylinder boxers. And now hardly anyone makes them anymore, the air-cooled engines.
Of course, air cooling has advantages
An air-cooled engine is easier to make, with fewer technical parts. An air-cooled engine is lighter. And those are all advantages if it is not all that important, especially in the early days of the combustion engines. If a motor is loaded higher, it quickly becomes less easy. In order to keep the case thermally healthy, quite a bit of work has to be done, for example, greater tolerances have to be used. And a lot of cooling surface has to be made in the form of cooling fins, which also all have annoying properties and limitations.
From the 20s onwards, something was added: all those tolerances and flapping cooling fins created more mechanical noise. And that was wrong. The disadvantages of air cooling are the dependence on the wind and the difficulty of cooling all cylinders evenly in multi-cylinder engines. Forced air cooling is usually the solution for these problems. But there is another problem: the limited specific heat of air. Air is simply not a good heat storage medium. Water dissipates heat much better, every recreational diver knows that after a winter dive of XNUMX minutes. I've never had the kind of compassionate looks from the senior cyclists who passed by when I was just naked after taking off my wetsuit.
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So a lot of air is needed to cool an engine
That is why the largest possible fan is used for forced air cooling. One thing that requires considerable power and makes noise, fortunately a nice noise. With a Duck all this is not too bad. But the fan of and 911 is simply very impressive. Such a fan blows air to all parts to be cooled via a tunnel system. And those parts are also equipped with cooling fins where the cooling of the combustion spaces and the area around the exhaust ports are the most important. This system was not only used for passenger cars.
Truck maker Magirus-Deutz also had forced air cooling for their large diesel engines. They were very popular as a motor sprayer with the fire brigade. The large air-cooled diesels had a unique sound and, when deployed, could stand for hours crying and doing their job where their water-cooled colleagues got too hot. And that sound? You never heard that again.
Pros and cons
The advantages of air-cooled engines are that they are lighter without the use of radiators, water pumps, thermostats, coolant or hoses. The disadvantages are that they do not heat up quickly and cannot maintain a constant engine temperature. This affects engine performance and emissions during climatic changes such as extreme cold or high temperatures. A cold engine requires extra fuel to function properly. But The Environment is the biggest disadvantage of this way of construction: More noise and higher emissions than with 'water' cooled engines meant that air-cooled engines became an endangered species and are now virtually extinct.
Strictly speaking, almost all engine blocks are ultimately cooled by air. Because with liquid-cooled engines, the liquid is an intermediate medium. The heat is brought to the radiator. And cooled there with wind.
The Best of Both Worlds (Roger Palmer)
Some engines can use a hybrid design that uses one water cooling combined with a number of air-cooled engine properties to keep the engine cool and to alleviate the added weight of a large water cooling system. These systems can use smaller radiators or thin lightweight radiators and engine designs with air-cooled areas to dissipate heat.