and carburetor. Dry sump engines in some drag racing cars use scavenging pumps to extract oil and gases from the crankcase. A separator removes the oil, then the gases are fed into the exhaust system via a venturi tube.. This system maintains a small amount of vacuum in the crankcase and minimises the amount of oil in the engine that could potentially spill onto the racetrack. References Engine valves Engine technology Pollution control technologies