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Intake manifold vacuum is applied to the crankcase via the PCV valve. The airflow through the crankcase and engine interior sweeps away combustion byproduct gases. This mixture of air and crankcase gases then exits, often via another simple baffle, screen, or mesh to exclude oil mist, through the PCV valve and into the intake manifold. On some ...
Crankcase dilution is a phenomenon of internal combustion engines in which unburned diesel or gasoline accumulates in the crankcase.Excessively rich fuel mixture or incomplete combustion allows a certain amount of fuel to pass down between the pistons and cylinder walls and dilute the engine oil.
An oil catch can is fitted in line of the crank case breather system. It is placed in between the breather outlet and the intake system. As the crank vapors pass through the catch can the oil droplets, un-burnt fuel, and water vapor condense and settle in the tank. This stops them from reaching the intake and causing the issues mentioned above.
This crankcase pumping effect (also found on single-cylinder engines and 360° parallel-twin engines) is usually addressed by means of a crankcase breather. [ 4 ] The Citroën 2CV boxer-twin engine took advantage of this pumping effect to maintain a partial vacuum inside the crankcase, in order to reduce oil leaks when an oil seal malfunctions.
Many two-stroke engines use a crankcase-compression design, where a partial vacuum draws the fuel/air mixture into the engine as the piston moves upwards. Then as the piston travels downward, the inlet port is uncovered and the compressed fuel/air mixture is pushed from the crankcase into the combustion chamber.
Because of the dry sump's external oil reservoir, excess air can escape the oil before the oil is pumped back through the engine. Dry sumps also allow for more power because they reduce the amount of windage, oil sloshing up into the rotating assembly, and the vacuum from the scavenge pump improves ring seal. [10]
EGR has nothing to do with oil vapor re-routing from a positive crankcase ventilation system (PCV) system, as the latter is only there to reduce oil vapor emissions, and can be present on engines with or without any EGR system. However, the tripartite mixture resulting from employing both EGR and PCV in an engine (i.e. exhaust gas, fresh air ...
More complex dry-sump systems may scavenge oil from other areas where oil may pool, such as in the valvetrain. Power can be further increased if the dry-sump system is designed to create a vacuum inside the crankcase, which reduces air drag (or 'windage') on moving parts as well. Improved pump efficiency to maintain oil supply to the engine.