Modern Automotive Technology PowerPoint for by Russell Krick Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois

Chapter 11 Engine Fundamentals

Contents Engine operation Engine bottom end Engine top end Engine front end

Engine Operation The engine is the source of power for the vehicle It converts the energy stored in fuel into motion

Engine Operation Fuel is burned inside the engine’s combustion chamber to produce heat Heat causes expansion of gases in the engine Expansion in the combustion chamber produces pressure Engine components convert pressure into rotating motion

Engine Operation

Piston Travel (TDC, BDC) Top dead center (TDC) piston is at its highest point in the cylinder Bottom dead center (BDC) piston is at its lowest point in the cylinder Piston stroke distance the piston slides up or down from TDC to BDC

Piston Travel (TDC, BDC)

Four-Stroke Cycle Requires four piston strokes to complete one cycle Every four strokes, the engine produces one power stroke Two complete crankshaft rotations are required to complete the four-stroke cycle Almost all automobiles use four-stroke-cycle engines

Intake Stroke Draws fuel and air into the engine Intake valve is open Exhaust valve is closed Piston slides down and forms a low pressure area in the cylinder Atmospheric pressure pushes the air-fuel mixture into the cylinder

Compression Stroke Compresses (squeezes) the air-fuel mixture, making it more combustible Piston slides upward Both valves are closed

Power Stroke Burns the air-fuel mixture and pushes the piston down with tremendous force Both valves are closed Spark plug fires, igniting the air-fuel mixture Pressure forms on the top of the piston Piston is forced down, rotating the crankshaft

Exhaust Stroke Removes the burned gases from the cylinder Piston moves upward Intake valve is closed Exhaust valve is open Burned gases are pushed out the exhaust port

Four-Stroke Cycle

Engine Bottom End Refers to the block, crankshaft, connecting rods, pistons, and related components Another name for the bottom end is the short block

Forms the main body of the engine Engine Block Forms the main body of the engine

Engine Block Parts Cylinders Water jackets large, round holes machined through the block Water jackets coolant passages through the block allow a solution of water and antifreeze to cool the cylinders

Engine Block Parts Core (freeze) plugs Main bearing bores Main caps round metal plugs that seal holes left in the block after casting Main bearing bores holes machined in the bottom of the block to hold the crankshaft Main caps hold the crankshaft and main bearing inserts in place

Crankshaft Harnesses the tremendous force produced by the downward thrust of the pistons Changes the reciprocating (up-and-down) motion of the pistons into rotating motion

Fits into the bottom of the block Crankshaft Fits into the bottom of the block

Journals are precision-ground surfaces for the bearings Crankshaft Parts Journals are precision-ground surfaces for the bearings

Crankshaft Parts Counterweight offsets the weight of the piston, rod, rings, and journal offset to prevent vibration

Crankshaft Parts Crankshaft snout Crankshaft flange sticks through the front of the block provides a mounting place for the camshaft drive mechanism, front damper, and pulleys Crankshaft flange holds the flywheel

Engine Main Bearings Removable inserts that fit between the block main bore and the crankshaft main journals One-half of each insert fits into the block, while the other half fits into the block main cap A main thrust bearing has flanges to control crankshaft end play

Oil holes and grooves allow oil to lubricate the bearings Engine Main Bearings Oil holes and grooves allow oil to lubricate the bearings

Main Bearing Clearance Space between the crankshaft main journal and the main bearing insert Allows lubricating oil to enter and separate the journal and bearing this allows the journal to rotate without rubbing on the bearing and causing excess wear

Engine Bottom End

Crankshaft Oil Seals Keep oil from leaking out the front and rear of the engine Seals are placed around the front and rear of the crankshaft to contain this oil Rear main oil seal one- or two-piece seal that fits around the rear of the crankshaft to prevent oil leakage Front main oil seal one-piece seal pressed into the front cover

Flywheel Large metal disk mounted on the rear of the crankshaft Flywheel functions: connects the crankshaft to the transmission or transaxle through a clutch or torque converter helps smooth engine power pulses contains a large ring gear, which meshes with the starting motor gear to start the engine

Connecting Rod Fastens the piston to the crankshaft Transfers piston movement and combustion pressure to the crankshaft rod journals Causes piston movement during the non-power producing strokes intake, compression, and exhaust

Connecting Rod

Connecting Rod Bearings Ride on the crankshaft rod journals Fit between the connecting rods and the crankshaft Rod bearing clearance small space between the rod bearing and crankshaft journal allows oil to enter the bearing, preventing metal-to-metal contact

Piston Transfers the pressure of combustion to the connecting rod and crankshaft

Allows the piston to swing on the connecting rod Piston (Wrist) Pin Allows the piston to swing on the connecting rod

Piston Clearance The amount of space between the sides of the piston and the cylinder wall Allows a lubricating film of oil to form between the piston and the cylinder Allows for expansion when the piston heats up

Piston Rings Seal the clearance between the outside of the piston and the cylinder wall Keep combustion pressure from entering the crankcase Keep oil from entering the combustion chambers

Piston Rings

Compression Rings Prevent blowby (compression pressure leaking into the engine crankcase) Compression and combustion pressure push the compression rings down in their grooves and out against the cylinder wall, improving sealing

Compression Rings

Oil Rings Prevent engine oil from entering the combustion chamber Scrape excess oil off the cylinder wall If too much oil gets into the combustion chamber, it will burn, causing blue exhaust smoke and increased exhaust emissions

Oil Rings

Ring Gap Split, or space, between the ends of a piston ring Allows the ring to be spread open and installed on the piston Allows the ring to be made slightly larger in diameter than the cylinder when installed in the cylinder, the ring spreads outward and presses on the cylinder wall, aiding ring sealing

Engine Top End Refers to the cylinder heads, valves, camshaft, and other related components These parts work together to control the flow of air and fuel into the engine cylinders They also control the flow of exhaust out of the engine

ENGINE TOP END

Cylinder Head Bolts to the deck of the cylinder block Covers and encloses the top of the cylinders Combustion chambers are small pockets formed in the cylinder head combustion occurs in these small pockets

Combustion chambers contain the spark plug tip and valve seats Cylinder Head Combustion chambers contain the spark plug tip and valve seats

Cylinder Head Parts Intake ports Exhaust ports route air (diesel engine) or air and fuel (gasoline engine) into the combustion chamber Exhaust ports route burned gases out of the combustion chamber

Cylinder Head Parts Valve guides Valve seats small holes machined through the cylinder head for the valves valves slide in these guides Valve seats machined surfaces in the combustion chamber port openings

When the valve is closed, it seals against the valve seat Cylinder Head Parts When the valve is closed, it seals against the valve seat

Consists of the valves and the parts that operate them Valve Train Consists of the valves and the parts that operate them

The camshaft lobe turns into the lifter and the valve is pushed open Valve Train Operation The camshaft lobe turns into the lifter and the valve is pushed open The lobe rotates away from the lifter and the valve spring pushes the valve closed

Located in the engine block or in the cylinder head Camshaft Located in the engine block or in the cylinder head

Camshaft Parts Cam lobes Eccentric Camshaft journals egg-shaped protrusions machined on the camshaft one lobe is provided for each engine valve Eccentric may be machined on the camshaft for a mechanical fuel pump Camshaft journals machined surfaces for the cam bearings

Valve Lifters Usually rides on the cam lobes and transfers motion to the rest of the valve train Located in the engine block or cylinder head Fit into lifter bores, which are machined holes in the block or head

Push Rods Transfer motion between the lifters and the rocker arms Needed when the camshaft is located in the cylinder block Made from a hollow metal tube with a ball or socket formed on each end One end fits into the lifter, while the other end fits against the rocker arm

Rocker Arms Used to transfer motion to the valves Mount on top of the cylinder head Rocker arm movement allows the camshaft lobe to force the valve open Valve spring force closes the valve and keeps the rocker arm in contact with the push rod

Open and close the ports in the cylinder head Valves Open and close the ports in the cylinder head

Intake Valve Larger than the exhaust valve Controls the flow of the air-fuel mixture (gasoline engine) or air (diesel) into the combustion chamber Fits into the port leading from the intake manifold

Exhaust Valve Controls the flow of exhaust gases out of the cylinder Smaller than the intake valve Fits into the port leading to the exhaust manifold

Valve Seals Prevent oil from entering the combustion chambers through the valve guides

Valve Spring Assembly Used to close the valve

Intake Manifold Bolts to the side of the cylinder head Contains runners going to each cylinder head port Air and fuel (gasoline engine) are routed through these runners

Exhaust Manifold Bolts to the cylinder head Fastens over the exhaust ports to carry burned gases to the exhaust system Made of cast iron, lightweight aluminum, or stainless steel tubing

Engine Manifolds

Valve (Rocker) Cover Thin metal or plastic cover over the top of the cylinder head Keeps valve train oil spray from leaking out of the engine

Engine Front End Operates the engine camshaft and sometimes the oil pump, distributor, engine sensors, and diesel injection pump Consists of a drive mechanism, a front cover, an oil seal, and a crankshaft damper

Camshaft Drive Needed to turn the camshaft at one-half engine speed Often called the timing belt, timing chain, or timing gears because they time the camshaft with the crankshaft

Camshaft Drive A belt-drive, chain-drive, or gear-drive may be used to turn the camshaft

Front Cover Bolts over the crankshaft snout Holds an oil seal that seals the front of the crankshaft When the engine uses a gear- or chain-type camshaft drive, the front cover may be called the timing cover

Engine Front End

Timing Belt The front cover houses the front oil seal. The timing cover fits over the belt.

Timing chain and sprockets operate the camshaft in this engine

Crank Damper Heavy wheel on the crankshaft snout Mounted in rubber Helps prevent crankshaft vibration and damage Also called the harmonic balancer or vibration damper