Control unit functions

Reference numbering of terminals (pin) on control unit

1. 32-way connector, red
2. 32-way connector, dark yellow

CONTROL UNIT FUNCTIONS

Starting and cold starting

During start-up, the injectors are controlled in two main stages:

• Prime Pulse (Prime pulse)
• Simultaneous Double Fire Crank

A prime pulse is administered as quickly as possible in order to minimise starting times. Pulse size depends on coolant temperature.

Simultaneous double fire crank occurs twice upon each crankshaft revolution in correspondence with teeth 22 and 52 of the phonic wheel and persists until 450 rpm is exceeded.

During cold starts, the mixture is enriched on the basis of mapped values according to temperature and absolute pressure.

Special anti-flood functions reduce enrichment if starting takes a long time.

Engine warm-up

The heating stage begins when the post-starting stage is over and lasts until conditions are suitable for entry into closed loop operation (lambda probe operating range). During this stage, the fuel mixture is enriched in inverse proportion to coolant temperature.

Enrichment during acceleration

Enrichment is implemented during acceleration in asynchronous manner according to information on butterfly valve angular changes and absolute pressure.

Requirement for/size of these factors is computed every 7.81 ms.

Heavy load

During operation under full load, the fuel mixture is enriched to allow the engine to deliver full power (achieved without a stoichiometric ratio) and prevent the catalyser overheating.

The lambda probe reading is disabled.

Fuel cut-off

When the accelerator pedal is released, engine temperature >40 °C, vehicle speed >20 Km/h and rpm >1750, the control unit cuts off injection (CUT-OFF). It is restored when speed drops below 18 Km/h and rpm below 1500.