Subject L - Ignition and Starting Systems Flashcards
What is a magneto?
A magneto is a self contained AC generator driven by the engine for the purpose of ignition in a reciprocating engine.
Why are magneto ignition systems preferred over battery type ignition systems for reciprocating engines?
Magnetos are independent ignition source and do not rely on battery power to provide ignition.
What can cause reciprocating engine to continue to run when the ignition switch is in the “off” position?
If there is a break in the p-lead wire from the magneto to the switch, then the ignition switch cannot ground the magneto primary circuit.
What is the purpose of the condenser in a high tension magneto electrical system?
To prevent arcing at the points and hasten the collapse of the magnetic field around the primary coil.
Where is the E-gap position?
The E-gap position is when the poles of the rotating magnet are a few degrees past the neutral position. E- gap is the position where the points begin to open.
What are the three major circuits of a high tension magneto system?
the magnetic circuit, primary electrical circuit, and the secondary electrical circuit.
What are the components of a high tension magnetic circuit?
the magnetic circuit consists of a permanent rotating magnet, soft iron core, and pole shoes.
What happens when the primary breaker points open in a magneto?
Opening the breaker points stops the flow of current to the primary coil.
The magnetic field that was emitted by the primary coil collapses.
As this magnetic field collapses, the flux lines that cut across the windings of the secondary coil induce a pulse of high voltage current in the secondary coil needed to fire the spark plugs.
What is the piston position when the spark occurs in the cylinder?
The piston is a specified number of degrees before Top dead center on the compression stroke.
What is dual magneto?
the dual magneto incorporates two magnetos into one housing. They share the rotating magnet and cam, however they have their own sets of points, coils, and distributor blocks.
What is the difference between a low tension and high tension ignition system?
In the high tension system, the high voltage is generated in the magneto and flows to the plugs through high tension leads.
In low tension systems, the low voltage is generated in the magneto and flows through low tensions leads to the primary winding of a transformer coil located near each spark plug. There the voltage is increased to high voltage by transformer action and is conducted to the plugs with very short high tension leads.
When the ignition switch is in the OFF position, what is the condition of the primary circuit?
It is completed through the ignition switch to ground.
What three conditions are required to fire plugs in a cylinder when the piston is in the prescribed position?
1) Magneto’s magnet poles should be in the E-gap position.
2) The breaker points must open and
3) The distributor rotor must be aligned with a distributor electrode for that cylinder
What is dual ignition system, and what part of the system is grounded when the ignition switch is placed in the RIGHT position?
A dual ignition system uses two separate magnetos with the harness arranged so that each magneto fires one plug in each cylinder.
If the switch is set to right, the left magneto will be grounded, preventing it from firing.
What is internal timing of a magneto?
It is adjusting the breaker points to open when the poles of the rotating magnet are in the E-gap position.
