Distributor recurving

The advance vs. RPM/vacuum characteristics of the distributor are modified to better suit the requirements of the engine, either by changing springs/weights in the original unit, or substituting parts designed for other MGA/MGB applications.

Points elimination

The points/condenser combination that normally switches the low-tension supply to the coil (and hence produces a spark) is replaced by an electronic switch for reduced resistance and reduced maintenance. The switch may itself be triggered by the closing of the points contact, but it is more common to fit an optical or magnetic switch that senses the distributor driveshaft position.

Programmable ignition

As well as replacing the points contact, the relation of the spark timing to the crankshaft position is varied according to a programmed 'map', generally by a microprocessor that senses position, RPM, vacuum and possibly other parameters. This enables much finer control of advance than the two springs and centrifugal weights in a conventional distributor, so the advance can be set to allow for almost any engine modifications.

Crank-sensing ignition

This is a programmable system that overcomes any remaining uncertainty in spark timing, due to mechanical tolerance in the distibutor drive. Instead it senses crankshaft position directly, by either magnetic or optical sensors, which is the method used in almost all modern car engines. Typically the distributing of HT is avoided by having multiple coils, therefore the distributor is completely eliminated.