TYPES OF LUBRICATION SYSTEMS
Now that you are familiar with the lubrication
system in general, you are ready to study the different
methods used to circulate oil through the engine. The
systems used to circulate oil are known as force-feed,
full force-feed, splash, and combination splash
The force-feed (or pressure-feed) system (fig.
5-18) forces oil from the crankcase to the main
bearings, camshaft bearings, and connecting rod
bearings. The oil enters a line or a channel from the
Figure 5-19.--Full force-feed lubrication system.
pump and then flows to the crankshaft bearings, which,
in turn, feed the oil into drilled passages in the
of the crankshaft and splash oil to the upper parts of the
crankshaft. From these passages it flows through holes
engine. The oil, thus thrown upward in droplets and
in the connecting rods. The cylinder walls, pistons,
mist, provides lubrication for the valve mechanisms,
and piston pins are lubricated by the oil thrown off
piston pins, and other moving parts. The splash system
from the connecting rods.
is rarely found on modern engines, because its
lubricating effect is too uncertain to meet today's
heavy operating demands. On a full crankcase, it could
mean over lubrication and a waste of oil, while on a
In the full force-feed system (fig. 5-19), all
partly filled crankcase, it could cause inadequate
lubrication and failure of the engine.
lubricated by oil under pressure from the pump. Oil
enters the crankshaft oil passages, passes to the
Combination Splash Force-Feed
connecting rod bearings, enters holes drilled in the
connecting rods, goes up through the rod passages to
The combination splash force-feed system (fig.
the piston pin bearings, and helps lubricate both the
5-20), as the term implies, depends on oil splash and
pistons and the cylinder walls.
pressure to accomplish engine lubrication. The oil
pump forces oil under pressure to the main and
camshaft bearings and the valve mechanisms. The
connecting rods, the pistons, piston pins, and cylinder
In the splash system, dippers on the connecting
walls are lubricated by dippers splashing oil into the
rods enter the oil in the crankcase with each revolution
Figure 5-20.--Combination splash force-feed lubrication
Figure 5-18.--Force-feed lubrication system.