Search Results

The engine deposits withwhich operators are concerned have their source in what is commonly called sludge. Sludge is composed of carbonaceous matter (either from blow-by or from high-temperature cracking); asphaltenes (oxidized oil products); ash (mostly lead oxide and iron bromide where gasoline is used, metals from wear and corrosion and dust from the air); and moisture from condensation. All these component parts of sludge vary greatly depending on engine design, operating conditions, fuel and lubricant used. The whole engine ina sense is a centrifuge and throws this variable called sludge to various parts of the engine. The dead spots collect most with the hottest portions covered with a brittle flint-like carbon or lacquer. In high output engines run for extended periods of time, ring sticking limits the time of complete overhaul. It causes increased cylinder and ring wear. Contrasted to this are sludges formed under cold weather conditions.

Engine performance (availability and operating costs), maintenance (parts affected) and life (general overhaul period) are today a problem of severe duty engine conditions. Severe conditions, generally, are measured in terms of high power output (horsepower per cubic inch of piston displacement or BMEP). Such operations have brought about high piston ring groove and valve guide temperatures, which greatly increase ring and valve sticking tendencies. In the case of some passenger car engines at high speed and some truck and bus engines overloaded, ring sticking is not a problem but high crankcase oil temperatures cause excessive oxidation resulting in varnish on piston skirts and overhead valve mechanism. Time between crankcase drains, alloy type bearings and blowby contamination all relate to the severity of engine conditions.