Kart engines use different methods to expel the heat produced by combustion: air-cooling, water-cooling, but also the cooling effect generated by the fresh blend entering the carter and combustion chamber. Evidently this last type is not sufficient in and of itself, but it often makes the difference between an overheated engine and one that works at the ideal temperature
The cooling system of the engine, particularly of the kart engine, can be realized with either a free-air or a water system. Though in the past all engines used the former (which exploits the air that comes into contact with the engine thanks to the kart’s movement, without any fan to push the air toward the engine), today practically all of them use water, circulated mechanically by a rotating pump in the engine cylinder to cool it.
It is a well-known fact that the engine, during combustion, produces energy both in the form of gaseous pressure (which presses on the piston and provides the torque and potency for propulsion) and in the form of temperature (heat). This has a partly deleterious effect and represents a loss of energy.
Heat, therefore, must be extracted to avoid damaging the parts of the engine,
particularly the liner, piston and piston ring, and avoid causing detonation, the involuntary and early combustion of the blend in the combustion chamber which can subsequently lead to engine seizure.
The cooling system has precisely this purpose: bring heat away from the hotter areas of the engine through the use of fluids (gases or liquids).
The hottest area of the engine is the combustion chamber, which reaches the maximum temperatures on the exhaust port side, where the burnt gases pass and the cool fresh blend practically never arrives.
Even the carter, despite not getting as hot, must often be partly cooled, because a volume of blend within the carter that has a lower temperature turns out to be denser, and therefore makes it possible to get more blend into the combustion chamber, and, consequently, better performance.
Cooling systems, as previously mentioned, can be free-air, forced-air, or forced liquid. In karts only the first and the third are (or have been) used.
The free-air system is the simplest but least effective. Substantially it functions by exploiting the air that hits the engine thanks to the speed of the kart and which, being colder, subtracts heat by cooling the engine itself. In this case the cylinder and cylinder head feature numerous fins designed specifically to increment heat exchange between the air and the cylinder.
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