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

YouTube - Soldiers blow up washing machine with a grenade