11 Chapter Engine Fundamentals

Objectives After studying this chapter, you will be able to: Identify the major parts of a typical automotive engine. Describe the four-stroke cycle. Define common engine terms. Explain the basic function of the major parts of an automotive engine.

Objectives Cite and demonstrate safe working practices related to engines. Correctly answer ASE certification test questions that require knowledge of the basic operation of piston engines.

Engine Operation Engine Fuel Combustion chamber Source of power for vehicle Fuel Energy source Combustion chamber Hollow area between top of piston and bottom of cylinder head where fuel is burned

Engine Operation (Cont.) Combustion produces heat Heat causes expansion of gases in engine Expansion causes pressure Piston, connecting rod, and crankshaft Convert pressure to motion Motion drives gears, chains, sprockets, and belts Move car, operate systems

Piston Travel Distance piston moves up or down Top dead center (TDC) Crankshaft limitation Top dead center (TDC) Bottom dead center (BDC) Piston stroke TDC to BDC distance

Piston Travel (Cont.) (Ford)

Four-Stroke Cycle

Four-Stroke Cycle (Cont.)

Four-Stroke Cycle (Cont.)

Four-Stroke Cycle (Cont.)

Engine Bottom End Block Crankshaft Connecting rods Pistons Related components

Engine Block Also known as cylinder block Cylinders Pistons Main body of engine Cylinders Large round holes machined through block Pistons Fit into cylinders Deck or deck surface Top of block surrounding cylinders Cylinder head bolts to deck

Engine Block (Cont.) Water jackets Core plugs or freeze plugs Coolant passages through block Core plugs or freeze plugs Round metal plugs Seal holes left in block from casting Prevent coolant leakage Main bearing bores Holes machined in bottom of block to hold crankshaft Contain removable bearing inserts

Engine Block (Cont.) Main caps Engine bedplate Crankcase Bolt to bottom of block Hold crankshaft and main bearing inserts in place Engine bedplate Large metal girdle that replaces all main bearing caps Crankcase Lowest portion of block Crankshaft rotates inside

Crankshaft Harnesses force produced by pistons Changes up-and-down motion into rotating motion Fits into bottom of engine block

Crankshaft (Cont.) Main journals Rod journals Precisely polished Fit into main bearings Rod journals Offset from main journals Connecting rods bolt to journals Revolve around centerline of crankshaft

Crankshaft (Cont.) Counterweights Snout Counteract weight of connecting rods, pistons, rings, and rod journal offset Prevent vibration Snout Sticks out of end of block Provides mount for camshaft drive mechanism, front damper, and fan belt pulleys

Crankshaft (Cont.) Flange Rod journals Flywheel bolts to flange Center of flange has pilot hole or bushing Transmission torque converter or input shaft Rod journals Arranged so always at least one cylinder on power stroke Force always being transmitted to crankshaft

Engine Main Bearings Fit between block main bores and crankshaft main journals Consist of two removable inserts Upper main bearing Fits into cylinder block Lower main bearing Fits into main caps or bedplate

Engine Main Bearings (Cont.) Oil holes and grooves Allow oil to flow through block, main bearings, and crankshaft Main thrust bearing Limits distance crankshaft can slide in block Flanges limit end play

Engine Main Bearings (Cont.) Main bearing clearance Space between crankshaft main journal and main bearing insert Allows oil to enter and journal to rotate without rubbing

Crankshaft Oil Seals Keep oil from leaking from front and rear of engine Rear main oil seal Fits around rear of crankshaft Front seal Prevents leakage around crankshaft snout

Flywheel Large metal disc mounted on rear of crankshaft Connects crankshaft to transmission or transaxle Very heavy Helps smooth engine operation Contains large ring gear used to start the engine

Connecting Rod Fastens piston to crankshaft Connecting rod bearings Transfers piston motion Connecting rod bearings Ride on crankshaft rod journals Fit between connecting rods and crankshaft

Piston Transfers pressure of combustion to connecting rod and crankshaft Piston head Top of piston Piston ring grooves Slots cut in piston for piston rings Piston oil holes Allow oil to flow through piston and onto cylinder wall

Piston (Cont.) Piston ring lands Piston skirt Piston boss Areas above and between ring grooves Piston skirt Side of piston below last ring Piston boss Reinforced area around piston pin hole Piston pin hole Hole in piston boss for piston pin

Piston Pin Also called wrist pin Allows piston to swing on connecting rod

Piston Rings Seal space between piston and cylinder wall Most pistons use three rings Two upper compression rings One lower oil ring

Piston Rings (Cont.) Compression rings Oil rings Ring gap Prevent combustion pressure from leaking into engine crankcase (blowby) Oil rings Prevent engine oil from entering combustion chamber Ring gap Split or space between ends of piston ring

Engine Top End Controls airflow and sometimes fuel into engine cylinders Controls flow of exhaust out of the engine (Chrysler)

Cylinder Head Bolts to deck of cylinder block and encloses top of cylinders Intake and exhaust ports Cast into cylinder head Intake ports route air Exhaust ports route burned gases out of engine

Cylinder Head (Cont.) Valve guides Valve seats Small holes machined through cylinder head for valves Valve seats Round machined surfaces in combustion chamber port openings

Valve Train Valves and operational parts Camshaft Lifters Push rods Rocker arms Valves Valve seals Valve spring assemblies

Valve Train (Cont.) (Ford)

Valve Train (Cont.) Camshaft Located in engine block or cylinder head Journals Cam lobes Drive gear Thrust plate Eccentric

Valve Train (Cont.) Valve lifter or tappet Push rods Rocker arms Rides on cam lobes and transfers motion to valve train Push rods Transfer motion between lifters and rocker arms Rocker arms Transfers motion to valves Rock back and forth opening and closing valves

Valve Train (Cont.) Valves Open and close ports in cylinder head Intake valves Control flow of fuel mixture Larger than exhaust valves Exhaust valves Control flow of exhaust gases out of cylinder

Valve Parts Valve head Margin Face Stem Keeper grooves Valve stem tip

Valve Seals Prevent oil from entering combustion chamber through valve guides (American Hammered Piston Rings)

Valve Spring Assembly Used to close valves Valve spring Retainer Two keepers Shield

Intake Manifold Bolts to side of cylinder head(s) Contains runners or passages going to each cylinder head intake port Air and fuel route through runners With fuel injectors, only air passes through runners Injectors extend directly into combustion chamber

Exhaust Manifold Fastens over exhaust ports Carries burned gases into exhaust system Heavy cast iron Aluminum Stainless steel tubing

Valve Cover Also called rocker cover Thin metal or plastic lid over top of cylinder head Keeps valve train oil spray from leaking out of engine

Intake and Exhaust Manifolds

Engine Front End All parts attached to front of engine Camshaft drive Front cover Oil seal Crank damper

Engine Front End (Cont.) Additional attached parts Oil pump Water pump Chain or belt tensioners Auxiliary drives or sprockets Engine sensors

Engine Front End Components (Chrysler)

Camshaft Drive Needed to turn camshaft at one-half engine speed Timing belt Timing gears Timing chain Times camshaft with crankshaft

Front Cover Bolts over crankshaft snout Holds oil seal that seals front of crankshaft Also called timing cover (Ford)

Crank Damper Heavy wheel on crankshaft snout Mounted in rubber Helps prevent vibration and damage Harmonic balancer Vibration damper