Engine management system - MEMS (Ignition components): Description and operation

Ignition components

Ignition coil - ’K’ series

The coil for the programmed ignition system is mounted on the back of the engine. The coil has a lower primary winding resistance (0.71 to 0.81 ohms at 20°C) than a coil in a conventional ignition system. This allows the full h.t. output to be reached faster and so makes the coil operation more consistent throughout the engine speed range.

Distributor cap and rotor arm - ’K’ series

1. Distributor cap
2. Rotor arm
3. Retaining screw
4. Anti-flash shield

The distributor cap, carrying a central carbon brush and four h.t. lead pick-ups, is located at the No.4 cylinder end of the inlet camshaft and surrounds the rotor arm. The rotor arm is secured by a retaining screw to a ’D’ shaped stub shaft, which is press fitted into a vibration absorbing bush in the camshaft, and is protected from oil contamination by an anti-flash shield which incorporates an oil drain.

Ignition coil - ’T’ series

The Quad output ignition coil is mounted on a bracket attached to the gearbox adaptor plate. The direct ignition coil used in a programmed ignition installation has a lower primary winding resistance (0.41 to 0.61 Ohms at 20˚C) than it’s conventional counterpart. This allows the full h.t. output to be reached faster and so makes the coil operation more consistant throughout the engine speed range.

FUEL SYSTEM

Engine Control Module (ECM)

The Modular Engine Management System (MEMS) is controlled by an ECM mounted on the bulkhead in the engine compartment.

The ECM is an adaptive unit which over a period of time learns the load and wear characteristics of the engine it controls.

The ECM remembers and updates two main engine requirements when the engine is running at normal operating temperature.

• The position of the idle air control valve required to achieve a specified idle speed. This is then used as a reference for idle air control valve movement to achieve idle speed under all load conditions.
• The fuelling change or offset required to achieve a set oxygen sensor voltage. This allows the system to provide the correct fuelling without having to apply excessive adjustments to the fuelling which can adversely affect the emissions and driveability.

NOTE: After fitting a different ECM, TestBook will be required to reprogram the ECM with the code from the anti-theft control unit and to perform a full engine tune procedure.