Lubrication Systems

2. 11 Lubrication Systems

3. Learning Objectives • Define friction and explain how it affects the internal engine components. • List the functions of lubricating oil. • Differentiate between the lubrication systems in two-cycle engines and four-cycle engines. • Explain the operation of ejection pumps, barrel pumps, and positive displacement pumps. • Explain the function of oil filter systems and differentiate between the three main types.

4. Lubrication • Reducing friction between sliding surfaces by introducing a slippery or smooth substance between them • Lubricant forms: • Dry (powdered) • Semidry (grease) • Liquid (oil)

5. Friction • Resistance to motion when one surface rubs against another • Even highly polished metal surfaces will create friction if rubbed together • Microscopic roughness will resist movement and create heat

6. Friction • As friction and heat increase, metal parts expand, causing even greater friction • Parts eventually weld themselves together or seize • In some cases, excessively worn parts may become too loose to function properly

7. Preventing Wear Due to Friction • Manufacturers select suitable material for parts in moving contact with each other • Rod and main bearings have a cast babbitt surface • All bearing surfaces have oil separating moving parts that are in close contact • Prevent metals from touching

8. Qualities of Lubricating Oil • Keeps engine parts clean • Detergent/dispersant additives • Cools engine parts • Seals combustion pressures • Prevents foaming • Aids fuel economy • Permits easy starting • Lubricates engine parts • Hydrodynamic lubrication • Boundary lubrication • Protects against rust and corrosion

9. Oil Specifications • Given in two ratings: • Society of Automotive Engineers (SAE) Viscosity • Also called viscosity grade • American Petroleum Institute (API) Engine Oil Service Classification • Referred to as type of oil

10. Viscosity • Viscosity is a measure of an oil’s resistance to flow • Keeps oil from being squeezed out from between engine surfaces as they move under pressure • Oil used must have viscosity characteristics that ensure satisfactory cold cranking, good oil circulation, and adequate temperature protection

11. SAE Viscosity Grade • Developed by SAE • All engine oils classified according to this system • Used worldwide

12. SAE Viscosity Grade • Each oil is assigned a grade that signifies the viscosity range into which it falls • Thick, slow-flowing oils have high numbers • Thin free-flowing oils have low numbers • W before grade number indicates that oil is suitable for use at low ambient temperatures

13. SAE Viscosity Grade Recommendations

14. Viscosity Index (V.I.) • Temperature effect on viscosity varies with different types of oils • Viscosity index is a measure of the relationship between viscosity and temperature • High viscosity number indicates little change in viscosity over a wide range of temperatures

15. Multigrade Oils • Multigrade, or multiviscosity oils meet the viscosity requirements of two or more SAE grades • SAE 5W-20, SAE 5W-30, and SAE 10W-30 • Can be substituted for single viscosity grades in four-stroke engines • Should not be used in two-stroke engines

16. API Engine Oils Service Classification System • Dynamic method of rating an oil’s suitability for use in various generations of engine • New categories created as oil is reengineered to meet growing demands placed on it by evolving engine designs

17. API Engine Oils Service Classifications • Divided into two categories: • “C” categories: classify oils suitable for use with compression-ignition engines • “S” categories: classify oils suitable for use with four-stroke, spark-ignition engines • Each successive “S” category is a suitable replacement for all the “S” categories that preceded it

18. API Engine Oil Categories for Spark-Ignition Engines

19. API Engine Oil Service Classification Symbol • Provides information about oil’s characteristics and applications • Typically found on oil container label • May also be found on oil fill cap or in owner’s manual

20. API Engine Oil Service Classification Symbol • Divided into three parts: • Top specifies oil’s service classification or recommended application • Center describes the oil’s viscosity • Bottom contains information on oil’s fuel-saving properties

21. Selecting the Proper Engine Oil • Always use type recommended by engine manufacturer • Shown on engine nameplate, oil filler cap, or label attached to engine • Also found in operator’s manual • API categories are not for two-stroke engines or those with wet clutch • Two-cycle oils contain additives that prevent unburned deposits

22. Engine Lubrication Systems • The way moving parts are lubricated differs in two- and four-cycle gasoline engines • In two-cycle engine, oil is mixed with gasoline and poured in tank • In a four-cycle engine, oil is poured into the crankcase

23. Two-Cycle Engine Lubrication • Two-cycle engine receives lubrication as fuel mixed with oil passes through engine • Clean oil continuously supplied to all moving parts while engine is running • Will get adequate lubrication even when operated at extreme angles • Oil eventually burns in combustion chamber and is exhausted with other gases

24. Mixing Fuel and Oil • The correct mixture of fuel and oil is critical in maintaining a two-stroke engine in good working condition • The prescribed type and grade of oil must be mixed with fuel in proper proportion before being placed in tank • Refer to manufacturer’s recommendations

25. Mixing Fuel and Oil • Amount of oil for given amount of fuel expressed as ratio • A fuel-to-oil ration of 40:1 requires 1 part oil for every 40 parts gasoline • Mix oil and fuel in separate container • Empty half of fuel from container • Add appropriate amount of oil • Place cap on container and shake • Add fuel that was removed and shake again

26. Two-Cycle Engine Fuel-to-Oil Ratio Chart

27. Four-Cycle Engine Lubrication • Provided by placing the correct amount and grade of oil in crankcase • Oil sump supplies lubrication for cylinder wall and all internal engine parts • Several methods used to feed oil from crankcase to correct locations • Must be operated in upright position for adequate lubrication

28. Splash Lubrication System • Oil dipper located on connecting rod cap • Picks up oil from crankcase on every revolution of crankshaft • Splashes oil on parts • Oil slinger used in place of dipper in some engines • Driven by crankshaft or crankshaft gear • Has several blades, or fingers, that pick up oil and splash it onto internal engine parts • Provides more consistent supply of oil

29. Constant Level Splash System • Contains oil pump, splash trough, and strainer • Pump supplies more oil to trough than dipper can remove • Oil returning to crankcase passes through strainer • System provides adequate lubrication as long as there is enough oil to supply pump • Engine can be operated at angle

30. Ejection and Barrel Pump Systems • Ejection pump system • Forces oil under pressure against connecting rod • Some oil enters connecting rod bearings, while remaining oil is deflected to other parts • Barrel pump system • Uses cylinder-and-plunger type pump • Oil is forced through passages in camshaft to the main bearing and connecting rod journals

31. Pressurized Lubrication Systems • Similar to systems used in automotive engines • Used in conjunction with splash system • Relies on positive displacement oil pump or rotor pump to supply oil to moving parts • Passages for oil flow are drilled to all critical points • Pressure relief valve prevents excessively high pressures at high engine speeds

32. Gear-Type Pump Operation

33. Oil Filter Systems • Used on engines with pressurized lubrication systems • Prevent harmful materials from circulating through engine • Oil filter prevents fine particles from circulating • Oil strainer prevents large particles from entering the filter

34. Filter System Types • Bypass filter system • Pumps part of oil through filter • Remaining oil pumped to engine bearings • Shunt filter system • Part of oil delivered by pump is filtered and directed to bearings • Remaining oil shunted past the filter and back into crankcase • Full-flow filter system • Directs all pumped oil through filter and to bearings

35. Bypass Filter System (Wix Filters)

36. Full-Flow Filter System

37. Low-Oil Warning and Shutdown Systems • Low-oil warning devices • Warn operator • Shut down engine • Limited to four-stroke engines

38. The resistance to motion created when one surface rubs against another is called _____. friction

39. To prevent wear caused by friction, all bearing surfaces must have _____ separating moving parts that are in close contact oil

40. List eight functions of modern motor oil. (Any order) Permits easy starting, lubricates engine parts, protects against rust and corrosion, keeps engine parts clean, cools engine parts, seals combustion pressures, prevents foaming, aids fuel economy

41. A two-stroke engine receives its lubrication as _____ mixed with oil passes through the engine. fuel

42. In a four-stroke engine, lubrication is provided by placing the correct quantity and grade of oil in the _____. crankcase

43. In an ejection pump system, oil is forced against the rotating _____. connecting rod

44. In a(n) _____ pump system, an eccentric on a hollow camshaft moves the pump plunger in and out of the pump cylinder. barrel

45. A positive displacement oil pump is used in a(n) _____ lubrication system. pressurized

46. Oil _____ prevent harmful materials from circulating through the engine. filters

47. Name the three basic types of oil filter systems commonly used on small engines. Bypass filter systems, shunt filter systems, and full-flow filter systems

48. True or False? In a bypass filter system, all the oil is pumped through the filter and directly to the engine bearings. False