Engine Terminology
Engine Dynamics
The Four Strokes
Lesson 6
March 2008
Spot Quiz
Laws of Mechanics Top 5 Bottom 5 Applied Laws of MechanicsYouTube - 3D animation of a car engine
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 gasses at the correct time.
In order for an engine to function properly:
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
BDC – meansBottom Dead Centre
TDC – meansTop 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)
Camshaft-the breathing brain
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 enginedamage could occur.
Timing Marks (Cam and Crank in sync)
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)
•Block
•Piston (rings)
•Wrist pin
•Connecting Rod
•Crankshaft
•Head
•Valve
•Spring
•Cam
•Belt (or other drive)
Top EndBottom End
Intake Stroke and Event
Intake valve OPEN Exhaust valve CLOSED Piston on down stroke
The 10 Pieces-Compression StrokeCause and Effect (advanced diagnostics)
•Block
•Piston (rings)
•Wrist pin
•Connecting Rod
•Crankshaft
•Head
•Valve
•Spring
•Cam
•Belt (or other drive)
Top EndBottom End
Compression Stroke and Event
Both valves CLOSED Piston on upward stroke
The 10 Pieces- Power StrokeCause and Effect (advanced diagnostics)
•Block
•Piston (rings)
•Wrist pin
•Connecting Rod
•Crankshaft
•Head
•Valve
•Spring
•Cam
•Belt (or other drive)
Top EndBottom End
Power Stroke and Event
Both valves CLOSED Piston on downward stroke
The 10 Pieces-Exhaust StrokeCause and Effect (advanced diagnostics)
•Block
•Piston (rings)
•Wrist pin
•Connecting Rod
•Crankshaft
•Head
•Valve
•Spring
•Cam
•Belt (or other drive)
Top EndBottom End
Exhaust Stroke and Event
Intake valve CLOSED Exhaust valve OPEN Piston on upward stroke
YouTube - How Engines Work
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