Page 249 - Mechanic Diesel - TT

MECHANIC DIESEL - CITS

When the ECU suddenly cuts off the flow of current to the ignition coil primary winding, the magnetic field col-
lapses. This results in the production of high voltage in the secondary winding which gives rise to a spark in the
spark plugs.

4 Distributor less ignition system
This engine has no distributor. In this system, two spark plugs are ignited at the same time. Out of these two spark
plugs, one provides ignition in one cylinder during its exhaust stroke. However, the ignition has no effect, as only
burnt gases are present inside the cylinder during the exhaust stroke.
The other spark plug ignites the mixture in another cylinder when the piston is at the end of the compression
stroke. Here normal combustion takes place.
In the ignition coil, there are two primary and two secondary windings. The rotary hall effect sensor on the
crankshaft controls the flow of current through the primary winding and consequently, the production of high
voltage in the secondary winding.
The trigger has two triggering points, one for each primary winding. Each triggering point sends a signal to the
electronic control unit (ECU) so that the flow of current through one of the two primary windings is stopped. When
the flow of current is stopped, the magnetic field in the primary winding collapses suddenly and a high voltage is
produced in the secondary winding.

A four-cylinder engine with the firing order 1,3,4,2 has a special arrangement in which cylinders 1 and 4 and
cylinders 3 and 2 are paired.
In a six-cylinder engine, which has no distributor, there are three pairs cylinders 1 and 4, cylinders 5 and 2, and
cylinders 6 and 3.
Each ignition coil is a true transformer.

236

CITS : Automotive - Mechanic Diesel - Lesson 71 - 75