A mechanism to maintain negative crankcase pressure in a turbocharged gas engine to meet Euro-VI emission regulation and to reduce oil consumption.

Emissions regulation continually drives the automotive industry to innovate and develop. This pushes to introduce mechanism to maintain negative crankcase pressure in gas engine to meet this changing regulation. The way a turbocharger is used, to meet engine performance, can impact the pressure balance over the compressor and turbine end seals. This pressure difference can allow oil to leak through turbocharger seals. In normal engine operating condition, the pressure in the turbocharger end housings is higher than the bearing housing and oil/gas flows into the bearing housing, through the oil drain to the crankcase. Under certain operating conditions, such as low idle and thermal management, this pressure difference can be reversed with a higher bearing housing pressure than the pressure behind the turbine compressor wheel. Under this condition oil/gas will flow out of the bearing housing to the recess behind the compressor wheel. The bearing housing pressure will always track the crankcase pressure. With negative crankcase pressure control management, the pressure in the bearing housing can be maintain lower than pressure behind the compressor wheel throughout all operating conditions including idling. Controlling negative crankcase pressure is through closed crankcase ventilation system with two different circuits, for normal operating condition and idling condition. A flow control valve in fluid communication with the crankcase and an intake manifold control the crankcase pressure in negative with reference to change in the intake manifold vacuum during an idling and motoring condition. The flow control valve is activated due to suction pressure at the intake manifold and fresh air is allowed via a bypass nozzle in a floating valve to regulate the crankcase pressure in negative within a threshold limit. A pressure-controlled valve in fluid communication with the crankcase and a clean side air intake pipe controls the crankcase pressure in negative with reference to change in air intake depression during a full and part load operating condition. The flow control valve is deactivated due to positive pressure at intake manifold so that crankcase pressure is regulated with respect to depression in the air intake pipe and rate of blow-by. By addressing oil leak from turbocharger seals through negative crankcase pressure management giving significance results in emission control especially in particulate number and reduction of oil consumption.