BOSCH Cis Fuel Injection - SAAB & VOLVO: Description

The Bosch Continuous Injection System (CIS) is a mechanically operated system. The system determines the amount of fuel to be injected into each cylinder by measuring the amount of intake air required to run the engine. Once the volume of air being drawn into the engine is known, the system can inject the correct amount of fuel to achieve a balanced air/fuel mixture.

An airflow sensor, made up of a round plate and lever assembly, moves up and down in relation to the air being brought into the engine. This assembly, in turn, raises or lowers a fuel control plunger or piston in the fuel distributor, resulting in exact measurement of fuel allowed to the injectors.

System is composed of an airflow sensor, fuel distributor, control pressure regulator, throttle valve housing, cold start valve, thermo-time switch, injectors, auxiliary air valve, and deceleration valve.

The auxiliary air regulator maintains proper idle speed by compensating for losses due to friction and condensation in the intake manifold and combustion chamber during cold engine starting. A bimetallic strip closes valve at about 158°F (70°C) or after 5 minutes engine operation.

Some models are equipped with CIS Lambda fuel injection system. System consists of the conventional CIS fuel injection system, with the addition of an oxygen sensor, a frequency/modulating valve, a throttle valve switch (Saab 900), a relay switch, an Electric Control Unit (ECU), and a 3-way catalytic converter (consisting of a honey-combed ceramic material coated with rhodium and platinum).

The CIS Lambda system operates in much the same manner as a conventional CIS system, but offers more precise fuel metering. This closer tolerance of injected fuel is controlled by the oxygen sensor which sends impulses to the ECU, which in turn sends control impulses to the frequency/modulating valve. This valve controls the time the injectors are injecting fuel. The 3-way catalytic converter further reduces CO, HC, and NOx.