Cylinder liner lubrication Friction between the cylinder liner and the piston rings is a major loss of power in the drive line of two-stroke diesel engines. Therefore, cylinder lubrication is very important on a four-stroke engine: the liner is 'splash lubricated from the oil that is leaving the surfaces of the big end bearing as it rotates during operation and a large volume of the oil w also be returned to the crankcase by the action of scrapper ring on the piston. Some four-stroke engines are provided with additional means of liner lubrication either from the lower part of the piston or from the a mechanism outside the cylinder liner that supplies oil through holes in the lower section of the liner. Either way the oil used is the same oil as the main engine lubricating oil. Some of the oil will find is way well-maintained trunk type past the piston rings and will be burnt. On average a large four-stroke engine will consume about 0.3-0.5 g/kWh of lubricating oil.
The two-stroke engine how has the liner separated from the crankcase by a diaphragm and the piston rod gland. Therefore, the cylinder liner must be lubricated by injecting cylinder lubricating oil onto the surface of the liner as the piston moves past the holes.
This system is a total loss lubricating system meaning that when the oil is injected to lubricate the cylinder and having completed its task the oil is either burnt or it comes out in the scavenge space. This system of having the two lubricating system separate means that a different cylinder oil can be used to the main lubricating oil for the engine.
As the lubricating oil is 'lost' it also means that this operation is costly and therefore as technology has improved so has the research into lowering consumption by studying the path of the cylinder oil through the engine. The problem has recently been compounded by the notification of the introduction of the use of LSF below 1.5% sulphur. Some manufacturers are recommending that two types of cylinder c are used. One to be used with the high sulphur fuel (HSF) (between 1.5% and 4.5%