Every combustion engine based vehicle has some sort of cooling system to help keep its temperature down. The heat generated is excessive and therefore must be removed to avoid significant engine damage, which could be permanent. A cooling mechanism is therefore important.
The most common cooling method today is the Liquid cooling system which consists of a green coolant flowing near the cylinder blocks absorbing heat and then going into the radiator. Repetition of this process helps keep the engine heat down. However, there was another technology which recently died with the sad demise of the VW Beetle back in 2003. This technology was known as air cooled and as the name suggests it worked by flowing air into the engine.
Though an air-cooled engine was hard to build, it was easy to maintain, unlike a liquid cooling engine. It was used extensively in motorcycles and petrol-engined tools since heat generation in such cases was less. Since these engines lacked radiator, water pump or water jacket and other similar accessories required in a liquid cooled engine to work, it meant that manufacturing an air-cooled engine was quite inexpensive. This in turn also reflected in the cars price.
How Air Cooled Engine Work
Air cooled engines are simple. First of all, there is a cool fan positioned in a semicircular ducting. This ducting also covers the cylinder head. The inside of the ducting help flows the air over the engine cooling fins along with an oil cooler. The air is then directed over a thermostat below the cylinders, which then operates a valve with the help of the lever. This valve is responsible to regulate the amount of air reaching the fan, which in return maintains the right engine temperature. Once the air has passed over the engine and thermostat, it then exits from the car from the rear by passing through a heat transfer system which is the exact same component responsible to pass hot air into the car’s cabin when you turn on the heater in cold winter days.
(Air Cooled)
Air Cooled Engines Deficiencies
Air-cooled engines are only efficient up to a certain degree of heat. They don’t do very well at high temperatures. This means you cannot squeeze more power out of such engines since large fans used to cool the engine can take away a lot of power. Taking away power is one issue but the noise they make is another one. Bigger the engine means bigger the cooling fan and hence a lot of unpleasant noise. Furthermore, with the passing of time as cars became more modernized, they also became faster. An air-cooled fast car would generate a lot of heat, hence requiring large amounts of energy to cool down the engine. This would also affect the car’s fuel consumption. This is where liquid cooled engines win over air-cooled engines.
Powerful air-cooled engines restrict the options of car stylists and designers since air-cooled engines are very shallow and broad. Air-cooled engines, in short, are not conducive for compact cars.
Air-cooled engines didn’t die out. They are still common in gensets, motorcycles, power saws, lawn mowers etc.
However air-cooled engines are not in fashion in cars anymore and the most important reason is emissions regulations which are applicable to car engines but not applicable to lawn mowers etc. Conventional carburettor engines left more of the fuel unburnt which removed combustion heat through the exhaust. Newer EFI engines let much less amount of fuel to remain unburnt, primarily to meet emissions standards and fuel economy. Unburnt fuel in engine exhaust is a carcinogen and causes birth defects etc plus it damages the CAT too which is fitted in the exhaust to control other types of emissions.
Less unburnt exhaust = more burnt fuel = more heat = requirement of better cooling system = water cooling becomes compulsory.