LUCAS "Opus" Electronic Ignition System: Description

Although the principle of operation of all Lucas "OPUS" electronic ignition systems is similar, variations do occur between models. See Figure.

For example, the XJ6 features a remote electronic control module (amplifier), while the TR8 has the control module mounted inside its distributor. Other models have the module mounted externally on the distributor housing. See Figure, Figure and Figure.

The XJ6 distributor is equipped with a gear-type reluctor (timing rotor) with one tooth for each cylinder. Other models use a timing rotor with ferrite iron rods (one for each cylinder) imbedded in its outside circumference. In all cases, the reluctor or timing rotor, mounted on the distributor shaft, rotates adjacent to a magnetic pick-up coil (module). The reluctor or timing rotor combines with the pick-up coil to generate signals to the electronic control module (amplifier).

All distributors feature centrifugal advance mechanisms and either vacuum advance or retard units. Some models, such as the TR8, feature ballast-drive resistor assemblies, while others such as the TR7, Spitfire and MGB use ballast wires during normal engine operation.

Other system components include the battery, ignition switch, and ignition coil.