Crankcase Ventilation

Crankcase Ventilation, 4-Cyl.:

Crankcase Ventilation

General
A new system of crankcase ventilation has been developed for the Saab 9-5. The new system differs from the previous system in that oil separation has been improved, the vacuum in the crankcase is more even and the volume of air entering the engine has been reduced. The latter is necessary to reduce the air volume on idle as the Saab 9-5 has air-flushed injectors.
The crankcase ventilation system on the Saab 9-5 has an external oil trap, a constant pressure valve and a shut-off valve.

Operation
Engine crankcase ventilation is of fully closed type. The ventilation system consists of a straight nipple mounted on the camshaft cover. The crankcase gases are carried via the nipple to the external oil trap connected to the crankcase by a hose via the camshaft cover. The constant pressure valve is connected to the oil trap by a hose and ensures that the pressure in the oil trap remains constant. The other end of the constant pressure valve is connected to the throttle body via a non-return valve and to the compressor intake via a shut-off valve. A return line runs from the oil trap to below the oil level in the sump.

On part load, the shut-off valve is closed and the constant pressure valve is connected to the throttle body to evacuate the crankcases gases here. On full load, there is pressure in the intake manifold and the vacuum in the constant pressure valve, the non-return valve is then closed and the shut-off valve open. The crankcase gases are evacuated to the compressor inlet where the gases are mixed with the intake air and combusted in the engine.

To avoid icing, the system is water-heated.

The shut-off valve is controlled by the TRIONIC engine management system.