When an internal-combustion engine (ICE) warms up, the air and oil vapors in the crankcase below the pistons heat up and expand. The pressure has to be released, so it’s usually routed into the intake manifold, so the engine can recirculate and burn these gasses. BMW has filed a patent application with the European Patent Office that proposes using a venturi pump to mix the crankcase vapors with fresh air before reintroducing it to the intake manifold, claiming there are several benefits by doing so.
Traditional Crankcase Ventilation
Automakers go about crankcase ventilation in different ways. The pressure differential between the crankcase and the intake manifold can feed the gasses to the intake, but it may also be pump-assisted. In either case, the gasses are simply routed back into the intake to be burnt as part of the combustion cycle, and no attempt is typically made to vary the extraction rate or control the flow to alter the oil-to-air ratio.
How BMW’s System Is Different
BMW’s patent doesn’t rely on a natural pressure differential to ventilate the crankcase, but uses a venturi-type suction-jet pump to extract the crankcase gasses. The system can mix these vapors with fresh air before sending them back into the intake manifold. BMW says that this can improve the engine’s efficiency. The system can vary the amount of fresh air that’s mixed in to reduce emissions. Also part of the system is an inertia-based oil separator that separates the oil from the air and sends it back to the oil pan.
A Potential Solution to Carbon Buildup in Direct-Injected Engines
BMW does not say what the cost of its system would be, or whether it would have additional service and maintenance requirements. The inertia-based oil separator in particular caught our eye, and should this device be effective at removing the oil from the intake air, it could potentially address another bugbear of engines without manifold injectors – carbon buildup on the intake valves. If BMW can satisfactorily address these concerns, it might draw the interest of other automakers to not only improve efficiency, but to reduce the ever-present carbon buildup on the intake valves of direct-injection engines.
