HEI High Power Ignition System (for engines 3.1 l)
Vehicles equipped with the HEI system use a special HEI ignition distributor with an electronic ignition distribution device (EST). The HEI distributors covered in this manual have a separate ignition coil.
All changes in the ignition timing adjustment in the HEI / EST distributor are carried out by the electronic control unit (ECM), which continuously reads data from various sensors installed on the engine, calculates the required ignition timing and instructs the distributor to make appropriate changes to the ignition distribution. Neither vacuum nor mechanical ignition timing controls are used here.
Electronic ignition control (ESC)
Engines with a working volume of 3.1 and 3.8 liters are equipped with an electronic ignition control system (ESC), which uses a knock sensor in conjunction with the ECM/PCM to control ignition timing, allowing the engine to achieve maximum ignition timing without knocking. This improves driving performance and reduces fuel consumption.
High voltage spark plug wires
The wires used in the HEI system are graphite-impregnated conductive cords encased in an 8 mm rubber sheath with an outer silicone insulation. This kind of conductor can withstand high temperatures well and is an excellent insulator for the high voltage generated by the HEI unit.
Attention! In the system NOT! an extremely high voltage is generated, therefore, when performing any work on the elements related to the ignition system, all safety precautions should be observed. This applies not only to the ignition distributor, control unit and high-voltage ignition wires, but also to parts related to the ignition system, such as spark plug contacts, tachometer and diagnostic equipment.
DIS direct ignition system
In this system, which does not have an ignition distributor, the ignition distribution is controlled by the PCM electronic unit. This system has no moving parts, eliminating the need for adjustment. The ignition coils installed in it are cooled more efficiently during operation and it itself requires almost no maintenance.
Direct ignition systems use a so-called ignition distribution method "extra candle". Each pair of cylinders has one ignition coil (1-4, 2-5, 3-6), as a result of which a spark appears simultaneously in the cylinder in the compression stroke and in the cylinder in which the piston is on the exhaust stroke. Because there is very little voltage drop across the spark gap in the exhaust cylinder, almost all of the voltage is used to ignite the cylinder on the compression stroke.
The DIS system consists of three coils, an ignition unit, a crankshaft position sensor (which uses the double Hall effect), a crankshaft vibration damper with crankshaft position sensor interrupt rings mounted on its rear shank, a camshaft position sensor, an ignition wire and a PCM control unit.
In conventional ignition coils, one end of the secondary winding is shorted to "mass". In direct ignition system coils, neither end of the secondary winding is connected to "weight"; instead, both ends are directly connected to the spark plugs in the opposite cylinders.
Double Hall effect magnetic crankshaft position sensors are mounted on an aluminum mounting bracket that bolts to the front valve cover. The interruption rings on the crankshaft damper provide interruption of the control voltage, causing a reaction "ON-OFF-ON-OFF" ("ON-OFF-ON-OFF") etc., reminiscent of the sequence of contacts in conventional ignition systems. The DIS system, like conventional ignition distribution systems, is equipped with an electronic ignition timing control unit (EST) and control circuit wires from the PCM.