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Engine Wear: Can occur on any of the surfaces in relative motion, i.e.piston bearing surfaces, bore, rings, grooves valve train, main and big-end bearings. However, the important wear that controls how long the engine can run between overhauls is mainly that of the bore at the upper limit of top ring travel, the radial wear of the top ring with resultant increase of ring gap and consequent blowby, and the increase of side clearance of the top ring due to ring and groove wear. Such wear may be due to abrasion by engine deposits or by foreign matter that enters through the air intake or the crankcase breathers. Abrasion by engine deposits usually increases with increase in the severity of operating conditions, but that due to adventitious matter is usually independent of operating conditions.
| | Provided air filtration is satisfactory, the main cause of wear of cylinder bores or liners is the corrosive action of inorganic acids derived from the sulfur in the fuel.In vehicle engines the thermostat ensures rapid warming up of the engine from cold,so eliminating much of the condensation of water produced during combustion and containing inorganic, mainly sulphuric,acid. However, even so, the dewpoint of the acids can be higher than the liner temperature at light loads, and will increase with gas pressure so that turbocharging makes matters worse. Furthermore, condensate on the lower portions of the liner can be swept upwards by the top ring where conditions of lubrication are least favorable and conditions for corrosion the most favorable. However, this type of wear can be kept within reasonable limits by the use of highly alkaline additives which neutralize the acids on the liner wall. | |
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