Car Engine Vacuum
What is Engine Vacuum?
Engine vacuum is a measure of the pressure difference between the inside of the engine’s intake manifold and the atmosphere. It is created by the downward movement of the pistons during the intake stroke. As the piston moves down, it creates a low-pressure area in the intake manifold, which draws air into the engine.
Engine vacuum is used to operate a variety of engine components, including the power brakes, power steering, and EGR valve. It can also be used to diagnose engine problems.
How is Engine Vacuum Created?
Engine vacuum is created by the downward movement of the pistons during the intake stroke. As the piston moves down, it creates a low-pressure area in the intake manifold, which draws air into the engine. The amount of vacuum created depends on the speed of the engine and the load on the engine.
At idle, the engine vacuum is typically around 15-20 inches of mercury (inHg). As the engine speed increases, the vacuum decreases. This is because the pistons are moving faster and creating more vacuum. The vacuum also decreases under load, as the engine is working harder to overcome the resistance of the load.
What are the Uses of Engine Vacuum?
Engine vacuum is used to operate a variety of engine components, including the power brakes, power steering, and EGR valve. It can also be used to diagnose engine problems.
Power Brakes
Power brakes use engine vacuum to assist the driver in applying the brakes. When the driver presses the brake pedal, a vacuum booster is activated. The vacuum booster uses engine vacuum to multiply the force applied by the driver, making it easier to stop the car.
Power Steering
Power steering uses engine vacuum to assist the driver in turning the steering wheel. When the driver turns the steering wheel, a vacuum-assisted power steering pump is activated. The power steering pump uses engine vacuum to multiply the force applied by the driver, making it easier to turn the steering wheel.
EGR Valve
The EGR valve (exhaust gas recirculation valve) uses engine vacuum to regulate the amount of exhaust gas that is recirculated back into the engine. EGR is used to reduce emissions by lowering the combustion temperature. Engine vacuum is used to open and close the EGR valve, controlling the amount of exhaust gas that is recirculated.
Diagnosing Engine Problems
Engine vacuum can be used to diagnose a variety of engine problems. For example, a low vacuum reading can indicate a vacuum leak, a faulty EGR valve, or a problem with the piston rings.
How to Test Engine Vacuum
Engine vacuum can be tested using a vacuum gauge. A vacuum gauge is a simple tool that measures the pressure difference between the inside of the intake manifold and the atmosphere. To test engine vacuum, simply connect the vacuum gauge to the intake manifold and start the engine. The vacuum gauge will display the vacuum reading in inches of mercury (inHg).
The following are some typical vacuum readings for a healthy engine:
- Idle: 15-20 inHg
- 2,000 RPM: 10-15 inHg
- 3,000 RPM: 5-10 inHg
If the engine vacuum reading is significantly lower than these values, it may indicate a problem with the engine.
Conclusion
Engine vacuum is an important part of the engine’s operation. It is used to operate a variety of engine components and can also be used to diagnose engine problems. By understanding how engine vacuum works, you can better maintain and troubleshoot your vehicle.
