What is the pressure reducing valve modified by Mitsubishi EVO for?

When driving a turbocharged car, when stepping on the accelerator to accelerate, the throttle will open, and with the increase of vehicle speed, the engine will make a "hmm …" sound. The exhaust energy discharged by the engine at high temperature and high pressure will drive the exhaust turbine to rotate. When the speed of the turbocharger reaches the working speed (that is, the turbine speed exceeds 654.38+ million revolutions per minute), the turbocharger will compress the surrounding air, so that the air intake of the engine will increase and the engine will be upgraded.

However, when we collect oil, the throttle opening decreases rapidly until it is in the closed idle state, which means that the engine does not need air intake, otherwise the air flow in the intake pipe will be blocked at the throttle. But at this moment, the turbocharger has not stopped working! Due to inertia, the turbocharger still keeps rotating at a speed of over 654.38+ million revolutions per minute. Now it is conceivable that the air is still being compressed into the intake pipe. If this part of high-pressure air cannot be discharged in time in the intake pipe, the pressure in the intake pipe will rise rapidly, and the acceleration will be delayed and uneven, which may damage the throttle or cause the intake pipe to burst.

At this time, it is necessary to install a pressure relief device in the intake pipeline to discharge the excess high-pressure air compressed by the intake turbine in the pipeline. In fact, the pressure reducing valve is a valve installed on the intake pipe to control the boosting pressure. The opening and closing of the pressure reducing valve is controlled by an electromagnetic coil operated by ECU (Electronic Control Unit). ECU will make a judgment according to the pressure of turbine outlet pressurization. Once the pressure exceeds the critical value, the electromagnetic coil will be turned on or off, and the pressure relief valve will be turned on or off.

When the pressure reducing valve is closed, it is based on ensuring that there is enough intake pressure in the intake pipe. When the valve is opened, it can release excess gas into the atmosphere, reduce the pressure in the intake pipe and protect the engine intake pipe. Therefore, the "hiss, hiss" sound we heard on the modified car is the sound when the pressure reducing valve releases pressure and exhausts.

In fact, the "hissing" sound from the modified car has no significance to the improvement of engine performance, and can only render the illusion of a large boost value. Relatively speaking, the greater the boost value of the engine, the more air discharged by the pressure relief valve, and the greater the theoretical noise. When refitting a car, it's cool to amplify the sound when the pressure relief valve releases pressure, or to process the sound, such as the whistle of HKS!