Ignition System: Description and Operation
IGNITION SYSTEMThis vehicle incorporates DLI (Distributorless ignition) system in order to increase the range of ignition timing and distributor voltage and to decrease electric wave noise. The components of this system are:
- Ignition Coil
- Camshaft Position Sensor
- ECM
- Spark Plug Wires and Spark Plugs
System Operation:
IGNITION SYSTEM OPERATION
In a conventional ignition system, the ignition coil produces a high voltage current and the distributor then relays this current, at the required time, to each spark plug. In the distributorless ignition system, two sensors, the camshaft position sensor and the crankshaft position sensor, tell the Engine Control Module(ECM) which cylinder is ready to fire. The ECM then sends an ignition signal to an electronic ignition coil. This ignition coil then produces and sends a high voltage current to the proper spark plug.
Distributorless ignition is a "wasted-spark" system in which two spark plugs fire simultaneously. One cylinder fires at TDC on the compression stroke, while the other fires at TDC of the exhaust stroke.
The cylinders are grouped together by firing order. For example, firing order is 1-3-4-2. Cylinders 1 and 4 are in the same position, while cylinders 2 and 3 are 180 behind. Plugs 1 and 4 fire together, as do the plugs in cylinders 2 and 3.
This means that an ignition spark is fired in one cylinder while at the same time a "waste" spark is fired in the companion cylinder.
Because of dualed plug firing, if an inductive tachometer is connected to a plug wire, it will indicate an engine RPM that is twice the actual speed (i.e., 1,600 RPM, instead of 800 RPM).
ELECTRONIC SPARK ADVANCE SYSTEM
Ignition Timing is determined and set within the ECM based on signals from various sensors and switches.
Optimum performance is gained with this system. The ECM varies ignition timing according to engine speed, intake air amount, coolant temperature and other conditions.
NOTE::
- Timing specification at idle is: 8 ± 5 °BTDC
- Timing is not adjustable
IGNITION SYSTEM COMPONENTS
The mechanical, rotating high-voltage distributor mechanism has been replaced by static electronically controlled components. These components are described below.
IGNITION COILS
Two ignition coils are used in this system. The engine locates them directly above the #2 and #4 spark plugs. The coil resistance is identical for these two coils, and there is no maintenance required for them. If determined to be faulty, they must be replaced.
SPARK PLUG CABLE
The spark plug cable connect the two ignition coils to the spark plugs. Their function is basically the same as on the previous system. Because of their shorter length, the DLI spark plug cable enhance the ignition systems delivered voltage. In addition, they reduce the wave interference from one high tension wire to another.
SPARK PLUGS
The spark plugs provide the air gap necessary to produce an arc from the electrical energy coming in from the ignition coil. This arc then ignites the fuel/air mixture in the cylinder, producing power.