Ignition Systems II

1. Ignition Systems II

2. Purpose of the Ignition System (review) • Create a spark strong enough to ignite the fuel air mixture. • Maintain the spark long enough to allow the for the combustion of all the air and fuel in the cylinders. • Deliver the spark at the right time during the compression stroke of each cylinder. • Maximum pressure should occur 10 to 25 degrees after TDC • Ignition must occur prior to TDC in order to complete the combustion cycle @ 10/25 dec ATDC.

3. Primary Circuit Components • Battery • Ignition switch • Ballast resistor (older systems) • Ignition coil primary winding • Triggering device • Switching device or control module

4. Secondary Circuit Components • Ignition coil secondary winding • Distributor cap and rotor (DI systems) • Spark plug cables (some systems) • Spark plugs

5. Note: This graphic does not include the capacitor/condenser in the primary ciruit.

6. Primary and Secondary Circuits

7. Types of Ignition Systems • Distributor (DI) systems • The voltage produced by the coil is sent to the distributor. • The spark is delivered to the cylinders through the rotor and distributor cap. • Distributorless (EI) systems • Have multiple coils that deliver the spark to each cylinder.

8. DISTRIBUTOR SYSTEMS • One coil fires all cylinders. • High voltage current is “distributed” to each spark plug via. the distributor rotor and Cap.

9. Distributor Systems • The primary components are: • Distributor • Rotor • Cap • Ignition Wires (cables) • Ignition Cables • Triggering Device

10. Distributor Systems • Primary circuit may be either “electronic” or mechanical. • Electronic uses a solid state sensor to make or break current flow in the primary circuit.

11. Distributor System • Mechanical systems use cam operated contact points to make or break current flow in the primary circuit.

12. Timing Control • Changes in ignition timing can be either mechanical, or electronic. • Mechanical Systems use: Centrifugal Advance Vacuum Advance (retard)

13. Timing Control • Changes in ignition timing can be either mechanical, or electronic. • Electronic Systems use the vehicles PCM and various engine sensors to control advance.

14. Mechanical Ignition Systems • Also called “Point and Coil. • Components • Power source • Distributor • Condenser • Contact Points • Cam • Rotor • Cap • Coil • Primary and Secondary Circuits • May have a starting ballast or resistor • Spark Plug

15. Types of Engine Position Sensors • Magnetic pulse generator • Consists of a reluctor and pickup coil. • Metal detection sensor • The electromagnet is in the pickup coil. • Hall-effect sensor • Produces a square wave signal. • Is most commonly used. • Photoelectric sensor • Uses an LED and moving slotted disc.

16. Magnetic Pulse Generator

17. Metal Detection Sensor

18. Hall Effect Sensor

19. Photo Electric Sensor

20. Distributor (DI) System Designs • External ignition module • Used on early Ford systems • Module mounted on the distributor • Ford’s TFI system • Module mounted inside the distributor • Most common design • Computer-controlled system

21. DI Systems – Computer Controlled Ignition Timing. • The goal of computerized spark timing is to do the following during all types of operating conditions: • Maximize engine power • Maximize fuel efficiency • Minimize emission levels • Timing strategy is based on engine operating conditions such as: • Crankshaft speed • Throttle position • Engine coolant temperature • Initial and manifold barometric pressure

22. DI Systems – Computer Controlled Ignition Timing. • The major areas of concern for programming ignition timing are: • Start-up • Speed related spark advance. • Load related spark advance • Warm-up spark advance • Special spark advance • Spark advance due to barometric pressure

23. DI Systems – Computer Controlled Ignition Timing. • Start-up. • During engine start up, computer control is bypassed. • Engine starts using the mechanical settings of the distributor. • Allows engine to start regardless of whether or not the computer is operating properly. • Once engine has started, ignition timing control is returned to the computer.

24. DI Systems – Computer Controlled Ignition Timing. • Speed related spark advance. • Advance timing for increased RPM and reduce advance for reduced RPM • Primary data: • Engine speed • Throttle position • Allows the computer to anticipate a change in engine speed.

25. DI Systems – Computer Controlled Ignition Timing. • Load related spark advance: • Improves power and fuel economy. • Uses: • Throttle position • MAP (Manif0ld Absolute Pressure) • Engine speed. • Typically, the heavier the load, the less advance is needed.

26. DI Systems – Computer Controlled Ignition Timing. • Warm-up spark advance • Primarily uses information from the coolant temperature sensor. • Typically, a cold engine requires more ignition advance.

27. DI Systems – Computer Controlled Ignition Timing. • Special spark advance. • Improves fuel economy during steady operating conditions. • Ignition timing will be greatly advanced during steady state operation.

28. Basic Distributor Type System

29. Distributorless Systems • Few newer cars are equipped with distributors.

30. Advantages of EI Systems • No moving parts • No distributor gears, bushings or shafts to wear out and cause erratic operation.

31. Advantages of EI Systems • Longer parts life • Don’t need to fire as often.

32. Flexible mounting locations

33. Advantages of EI Systems • Less radio frequency interference • No rotor air gap • Elimination of moisture/ozone related failures common with a distributor cap.

34. Advantages of EI Systems • No timing adjustments • No adjustments necessary to compensate for wear. • More time for coil saturation • Even in a waste spark system, twice the amount of time is available. • Computer will limit “Dwell-time” so that only enough time is alloted to fully saturate the coil.

35. An EI System with a Double-Ended Coil One plug fires during the compression/power stroke and the other fires during the exhaust stroke. This creates a “waste spark”

36. Distributorless EI System • Each plug in a plug pair will ground with a different poliarity. • Because of the high voltages involved (up to 100,000 V) the basic ground of the vehicle is irrelevant. • The “waste” plug has very little resistance so full current flow and voltage is available for the working plug.

37. Cableless EI System • Similar to other distributorless system except that the paired coils are enclosed.

38. Coil on Plug • Each coil is mounted directly on the spark plug. • Advantages: • No plug wires to: • Come loose • Create EMI • Burn • Break • Short (moisture or mechanical) • Disadvantage • Must remove coil to replace plug.