1. Early wipers were often driven by a vacuum motor powered by manifold vacuum . 2. There are no sensors for air flow, or intake manifold vacuum . 3. In naturally-aspirated petrol engines, the manifold vacuum is used, whereas in non-return valve. 4. Vehicle HVAC systems also used manifold vacuum to drive actuators controlling airflow and temperature. 5. Ideally, to preserve driveability and fuel economy, manifold vacuum should not fall any lower than. 6. When the throttle is partially closed, a manifold vacuum develops as the intake drops below ambient pressure. 7. At wide open throttle, manifold vacuum decreases. 8. The system is manifold vacuum -assisted servo-operated, and controlled directly by the Bosch engine management system, as described above. 9. If the engine is operating under light or no load and low or closed throttle, there is high manifold vacuum . 10. Intake manifold vacuum is applied to the crankcase via the PCV valve, drawing fresh air into the crankcase via the breather.
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