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Engine Terminology. Engine Dynamics The Four Strokes. Lesson 6. March 2008. Spot Quiz. Laws of Mechanics Top 5 Bottom 5 Applied Laws of Mechanics. YouTube - 3D animation of a car engine. In order for an engine to function properly:.
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Engine Terminology Engine Dynamics The Four Strokes Lesson 6 March 2008
Spot Quiz • Laws of Mechanics • Top 5 • Bottom 5 • Applied Laws of Mechanics YouTube - 3D animation of a car engine
In order for an engine to function properly: • the correct fuel charge must be delivered to the cylinder at the correct time. • ignition of the fuel charge must occur at the correct time. • the cylinder must be purged of spent gassesat the correct time.
Simplified • An easier way to remember is that an engine must have: • Spark • Fuel • Time
Engine breathing dynamics 1) Intake 2) Compression 3) Power 4) Exhaust
Crankshaft – stroke control In true terms, a stroke is the upward or downward movement of the piston in the cylinder from TDC to BDC once (1)
TDC - BDC TDC – means Top Dead Centre BDC – means Bottom Dead Centre
The ‘stroke' is the measurement between crankshaft main journal and connecting rod journal (throw) multiplied by 2
Crankshaft Rotation- 4 strokes 720 degrees (two revolutions) 0 - 180 180-360 360-540 540-720
The 4 Events • Intake (suck) • Compression (squeeze) • Power (bang) • Exhaust (blow)
Remember how the Crankshaft sees 720 degrees ? 0 - 180 180-360 360-540 540-720
How the Camshaft views 720 degreesof Crankshaft rotation How many times did the camshaft turn to complete all four events?
Crank-Cam ConnectionMechanical Valve Timing The camshaft is timed (aligned) to the crankshaft so that the valve ‘events’ occur during the appropriate ‘stroke’. This alignment must be precise or engine damage could occur.
Remember • Stroke is the piston moving from TDC to BDC once (controlled by crankshaft) • Event is opening and closing of valves (controlled by camshaft and valve springs)
The 10 Pieces - Intake StrokeCause and Effect (advanced diagnostics) Bottom End Top End • Block • Piston (rings) • Wrist pin • Connecting Rod • Crankshaft • Head • Valve • Spring • Cam • Belt (or other drive)
Intake Stroke and Event • Intake valve OPEN • Exhaust valve CLOSED • Piston on down stroke
The 10 Pieces-Compression StrokeCause and Effect (advanced diagnostics) Bottom End Top End • Block • Piston (rings) • Wrist pin • Connecting Rod • Crankshaft • Head • Valve • Spring • Cam • Belt (or other drive)
Compression Stroke and Event • Both valves CLOSED • Piston on upward stroke
The 10 Pieces- Power StrokeCause and Effect (advanced diagnostics) Bottom End Top End • Block • Piston (rings) • Wrist pin • Connecting Rod • Crankshaft • Head • Valve • Spring • Cam • Belt (or other drive)
Power Stroke and Event • Both valves CLOSED • Piston on downward stroke
The 10 Pieces-Exhaust StrokeCause and Effect (advanced diagnostics) Bottom End Top End • Block • Piston (rings) • Wrist pin • Connecting Rod • Crankshaft • Head • Valve • Spring • Cam • Belt (or other drive)
Exhaust Stroke and Event • Intake valve CLOSED • Exhaust valve OPEN • Piston on upward stroke YouTube - How Engines Work YouTube - Soldiers blow up washing machine with a grenade