Ignition & Starters Flashcards
When does the ignition event take place in a four stroke engine?
During the compression stroke
3 types of ignition systems:
Battery
Magneto
FADEC
What does FADEC stand for?
Full Authority Digital Engine Control
What is FADEC?
A solid state digital electronic ignition and sequential port fuel injection system
What does FADEC monitor?
Manifold Air Pressure (MAP)
Manifold Air Temp (MAT)
Engine Speed (RPM)
Cylinder Head Temp (CHT)
Exhaust Gas Temp (EGT)
Ignition
Timing
Fuel Mixture
ECU (electronic control unit) is the heart of the FADEC system. What does it contain?
Contains two microprocessors that control two cylinders
What are the types of magnetos?
Low & High tension
Rotating Magnet
Single or Double
Flange or Base
What does a low tension magneto require?
A secondary coil for each spark plug
What does a high tension magneto contain?
Contains Both a primary and secondary coil in the magneto
(Most common)
How many degrees apart are the two north poles of a four-pole magneto?
180 degrees
What is inside of a double magneto?
One housing
One magnet
One cam
Two sets of points
2 coils (primary & secondary)
2 capacitors
2 distributors
What are the three magneto circuits?
Magnetic
Primary
Secondary
What is a magneto’s permanent magnet made of?
Alnico
Aluminum
Nickel
Cobalt
Where is the ignition switch found?
In the primary circuit
The direction of the magnetic lines of flux is. always from ______ to ______ pole
North to South
What is a Keeper?
A laminated soft-iron bar placed across the poles of the rotating magnet to reduce the loss of magnetism
In magneto operational theory:
As speed increases…..
Voltage output increases
What are the 3 magnet rotational positions?
Full Register
Neutral
E-gap
What is Full Register?
The position of the magnet when all of the lines of flux are passing through the coil core
What is the Neutral position?
The position of the magnet when no lines of flux are passing through the coil core
Where does the rotating magnet pass through?
The E-gap position
How many turns of large insulated copper wire are in the Primary Circuit?
Relatively few
How many turns of very fine insulated copper wire are in the Secondary Circuit?
Several thousands
The magnetic field, caused by the primary current, collapses when the breaker points open. As this field collapses, what happens?
It induces a voltage in the secondary winding of the magneto coil
When do the breaker points in a high-tension magneto open?
When the rotating magnet is in the E-gap position
What is E-gap?
The position of the rotating magnet that is rotationally a few degrees beyond neutral
What is the Cam Follower?
A plastic device that contacts the breaker points to open them
What does cam follower wear cause?
Causes the timing to drift late or retard the spark
What is the compensated cam?
Has a separate cam lobe for each cylinder due to the elliptical path that the link rods follow
What does the capacitor do?
Acts as a storage chamber to absorb the sudden rise of voltage in the primary coil when the points begin to open
What does the capacitor prevent?
Prevents arcing between the contact points
(Burned points = Bad capacitor)
How do you remove grease or carbon tracks?
Acetone and lint-free cloth
The distributor gear always turns at _____ of the engine crankshaft speed.
1/2
What do the numbers on the distributor block show?
The magneto sparking order
NOT the firing order of the engine
What is Flash over?
Arcing across the incorrect path or surface
How can flashover due to high altitude flight be eliminated?
Pressurized magnetos