What is vacuum degree?

Generally speaking, the vacuum in an automobile refers to the negative pressure in the intake manifold. Due to the increase of the air flow rate sucked by the piston into the intake manifold and the opening and closing of the throttle body, a vacuum is formed in the intake manifold, and its function is to provide negative pressure. In order to meet the needs of various working conditions and save energy, many automobile parts are designed to be driven by vacuum, such as EGR valve, fuel pressure regulator, carbon canister and four-wheel drive front axle actuator. Automatic air conditioning mode switch (Buick's old car), etc. The other is to let the engine ECU know the current intake state of the engine through calculation and conversion by using the change of vacuum degree through the varistor, so as to control the fuel injection quantity and meet the requirements of the engine under various working conditions.