This promotes galvanic corrosion where metals of high nobility sacrifice themselves to metals of lower nobility – this is often manifested by pitting.Ĭorrosion inhibitor formulations have changed many times over the years, but not always for the better. Water also acts as an electrolyte if dissolved solids, such as hardness salts (lime scale) etc., are present. This cycle leads to a perpetual cycle of corrosion, which is accentuated in classic vehicles with no expansion chamber. Water when heated drives off a significant proportion of dissolved oxygen, but as it cools reabsorbs fresh oxygen. Boil-Over when running and After-Boil when the engine is stoppedĬaterpiller state that “Over-heating is the most common cause of engine down-time and responsible for >50% of catastrophic engine failures”.Īlthough water is cheap and readily available, it is also the root cause of corrosion within engine cooling systems.Cavitation caused by vapour escaping – due to pressure drops occurring within the cooling pump.Erosion caused by pitting around the liner, cylinder head and coolant pump.Reduced combustion efficiency and detonation issues in fuel injected engines.Pre-ignition (engine knock) in carburetted engines.Distortion of the cylinder head and liners.This over-heating and excessive thermal stress leads to several problems including This leads to a vicious cycle of over-heating. Because steam dissipates less than 1/30th of the heat that water does, local metal temperatures over-heat rapidly. This is also referred to as Film Boiling. When DNB occurs in an engine cooling system a film of steam bubbles form adjacent to the engine hot-spots (A in Fig.1). Evans have proven that in these areas Glycol-Water mixtures regularly cross the thermal boundary that separates Efficient Nucleate Boiling (B in Fig.1) from Inefficient Critical Heat Flux (CHF).ĬHF is synonymous with the condition Departure from Nucleate Boiling (DNB). Within an engine cooling system the hottest surfaces are those adjacent to the combustion chamber, specifically the cylinder liners and cylinder head. ![]() Evans Waterless Coolants represent a major step forward in engine cooling and engine protection technology. All such mixtures have inherent physical and chemical limitations that restrict engine performance and affect reliability. ![]() Since the 1930’s engine coolants have been based on a mixture of ethylene glycol, water and corrosion inhibitors. Now that Dreamscience “off the shelf” performance Packages are now touching 500bhp in some cases you need to make sure that you look after your Engine and one of the most important properties that you need to control and kept within optimum range is the engine coolant temperature, if this isn’t taken care of it will have a knock on effect on the Oil temperatures, Air intake temperatures, Overall engine power output and Ultimately its reliability.
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