HOW THE ENGINE WORKS

CYLINDER BLOCK
n The cylinder block is the foundation to which all other components are attached.

PISTON and ROD
n Cast Piston
n Forged Piston
n Barrel Skirt
n Slipper Skirt

CRANKSHAFT
n Changes Recipro-cating motion to Rotating motion

PISTON CONFIGURATIONS
n Inline 6
n Inline 4
n Opposed 4
n V-6
n V-8

OTHER ENGINE ID’S
n Valve Train Type
• Flathead
• Overhead Valve (OHV)
• Overhead Cam (OHC) or (SOHC)
• Dual Overhead Cam (DOHC)
n Engine Displacement
• Know conversion Factors From CI to CC
• CC to CI

DEFINITIONS
n TDC
• Top Dead Center
• Piston at top of stroke.
n BDC
• Bottom Dead Center
• Piston at Bottom of stroke.
n STROKE
• TDC to BDC
• BDC to TDC
• 180 degrees of crankshaft rotation
n FOUR CYCLE (Stroke)
• 4 x 180 = 720 degrees to make one complete cycle.

FOUR STROKE CYCLE
n Intake
Compression
n Power
n Exhaust

IGNITION
n Spark Ignition (SI)
• Gasoline Engines use a precisely timed electric spark to start the combustion process.
n Compression Ignition (CI)
• Diesel Engines use the heat produced from compression to raise cylinder temperature above the flash point of diesel, and inject fuel directly into the cylinder.

CAMSHAFTS
n Camshafts turn at one half crankshaft speed.
n Camshafts can be driven with a gear, chain and sprocket, or toothed belt.
n Camshafts have one lobe for each valve.

INTAKE STROKE
n Intake valve open
n Exhaust valve closed
n piston traveling down from TDC to BDC
n Air is being force into the cylinder by the difference between atmospheric and cylinder pressure

VACUUM DEFINITION
n Any pressure less than atmospheric in a sealed or semi-sealed container
n Approximately 14.7 PSI at sea level
COMPRESSION
STROKE
n Both valves closed
n Piston traveling up BDC to TDC
n Compressing the air-fuel mixture

POWER
STROKE
n Both valves closed
n Spark plug ignites the air fuel mixture
n Piston is being pushed down by the expanding gases from TDC to BDC

EXHAUST
STROKE
n Exhaust valve open
n Intake valve closed
n Piston traveling up from BDC to TDC forcing the burnt exhaust gases from the cylinder

n At TDC the engine has returned to its starting point.