The ideal ignition event in a cylinder has a flame originating at the tip of the spark plug and spreading out across the bore from there. Only one flame should exist. If another rogue flame is created it is identified as abnormal combustion. Depending on where in the piston's stoke the abnormal event happens will define pre-ignition or detonation. The enthusiast does not qualify the beginning of the abnormal combustion event and simply identifies it as knock or ping.
Anyone that has some experience with fighting knock knows that octane is only one of the areas that need to be addressed. Often throwing octane at an engine, especially a high compression or boosted one, does little to control knock. By definition octane is the fuel's ability to resist heat and pressure and wait for a spark to ignite. Low octane fuel is more anxious to ignite when exposed to heat or cylinder pressure. Likewise, higher-octane gasoline will withstand more of these elements. Abnormal combustion is the result of extreme cylinder pressure or heat and in most instances a combination of the two.
In an engine the radiator is used to remove heat from the coolant but the liquid has the job of cooling the engine and especially the cylinder head and combustion chamber. This fact is often not recognized since a temperature gauge reads the amount of heat in the liquid and not the surface temperature of the combustion chamber. The metal surface temperature is where detonation begins and needs to be addressed.
High cylinder head metal surface temperature, be it either local or general, can affect the performance of an engine. Excessive heating can lead to a loss of strength.
If detonation occurs and is severe enough the piston can either melt or erode the top land region. Where the damage occurs on the piston usually is the hottest region and coincides with the area that the end-fuel spontaneously ignited. At the least abnormal combustion will cost the engine power and fuel economy.
Heat is transferred from the cylinder bore and the cylinder head walls to the liquid coolant. As the coolant reaches the hottest part of the cylinder head (around the combustion chamber and exhaust valve) it will actually start to boil. This phase change is identified as the nucleate boiling point and allows the efficient transfer of heat from the metal surface to the liquid coolant. The coolant’s chemical and thermal reaction is responsible for how efficient this process becomes. In many cases efficient nucleate boiling changes phase once again to ‘Departure from Nucleate Boiling’ making the heat transfer process inefficient.
Once you grasp the job of a coolant you recognize that the traditional coolant mix with water is very poor at the task of cooling the cylinder head. Straight water is even worse but many still falsely think that it is a good choice. If you want to limit detonation then a better coolant needs to be used.
Evans Cooling Systems has developed a product called Evans Waterless Engine Coolant that has a lower surface tension than water and traditional coolants and boils at 190 degrees C at atmospheric pressure. Evans remains in its liquid form and keeps a constant and efficient heat transfer from the metal surface. This allows Evans to remove more heat from the cylinder head. The unique chemistry is also waterless and can be used in any petrol and diesel engine. All that needs to be done is a complete drain of the water-based coolant.
Evans, in conjunction with a non-restrictive cooling system helps to eliminate abnormal combustion at the root cause—excessive combustion chamber temperature. It not only adds life to the engine but allows for greater power and fuel efficiency from every drop or fuel consumed. Who would have thought that a coolant could do that?