Ignition Systems
What substances that for electrolyte in a battery?
An Electrolyte is a substance containing free ions that make the solution electrically conductive. There are two substances that form electrolyte in an Automotive/Marine battery. An acid solution, usually sulfuric acid, mixed with water forms the electrolyte that floods round the lead inserts. As electricity is pumped into the battery it is stored within this solution.
What three elements are required to make a petrol engine run efficiently?
A four stroke and two stroke engine requires three elements to run. Air, Fuel and Spark. In the absence of any of these three components the enginne will not run. Note that a 2 stroke engine needs lubrication added to the fuel or an engine seizure will occur.
Explain the 'Kettering ignition system' and its components.
This ignition system consists of;
Battery: This is an eletricity storage device.
Ballast resistor: This is used to limit the amount of current in an electrical circut.
Ignition coil: This is a major component within the ignition system. It consist of a primary winding wraping around a more concerntrated secondary winding. This device is used to boost the current from the battery to ingnite the fuel.
Distributor: Once the high energy charge has left the coil it is transfered to the distributor, this unit the distributes the spark between the sparkplugs using the rotor within it.
Capacitor: This is a small unit designed to stop the charge from the coil jumping the gap between the points as the voltage increases.
Points breaker: The points are where the connection between the coil and the spark plugs is connected and disconnected.
High-tennsion leads: These leads are used to transfer the high voltage from the distributor to the spark plugs.
Spark plug: This is the final comonent in the ignition system. The spark plug uses a high energy current to arch across its self igniting the fuel.
Electricity is feed through the ballast resistor to the Ignition coil. Current flows into the coil charging up the primary windings, as the distributor points are open (A capacitor within the distributor stops the coil from arching across the point gap). As the distributor rotates and the points close, the primary coil is collapsed into the secondary winding (consisting of several thousand turns of a very fine wire) boosting the voltage to 30-40 thousannd volts. The secondary winding is then channeled through the distrubutor points, rotor, high-tension leads to the spark plugs.
Explain 'Dwell angle' in a distributor.
The Dwell angle refers to the length of time the points are closed on a distributor. This is measured by degrees of rotation on the distributor shaft. Generally the manufacturer will recommend a dwell angle of 54 degrees.
Why is the heat range of a spark plug important?
The heat range is important for a number of reasons. If the tip of the spark plug gets too hot it can cause problems such as pre-ignition or detonation. If the tip of the plug is too cold then deposits can form on the insulator reducing spark current or shorting the spark plug.
What is a 'Capacitor discharge' ignition system and how does it work?
This sytem is different from the conventional kettering system. Consisting of a transformer, charging circut, rectifier, capacitor, coil and spark plug. Voltge is raised by the small transformer to betweenn 400-600volts annd then transfered to the charging circut to charge the capacitor. A rectifier in the charging circut is used to ensure the capacitor does not discharge before the moment of ignition. When sensors determine ignition timing the charging system is cut allowing the capacitor to discharge into the coil. This then raises the voltage again discharging up to 40,000volts out through the spark plug.
Referrences
Ed May Vol 1
Ed May Vol 2
Very good answers, I hope you have taken on board what you have presented to me.
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