Pressure relief valve in the car use

     When a modified car speeding off from the side, we often hear the "hum ......" After a period of accelerated engine sound, came the "ci ......" bang - it gives people a

momentum transfer full of feeling. This is where the sound is coming from? Why on ordinary civilian car, or some high-performance sports cars do not have such a voice (and some ordinary modified car there)?
     In fact, this unique "ci ......" sound is the sound pressure relief valve turbocharged engine emitted when the Safety Valve can be said that all of the turbocharged engine will produce this sound, but for everyday civilian vehicles , the manufacturers would this sound as noise to deal with in the design, to reduce it as much as possible. Approach is to vent the pressure within the intake manifold, so very little noise - this stove valves method is called internally drained.
When we depress the accelerator pedal acceleration, throttle opening, engine exhaust temperature and high pressure exhaust energy driven rotation of the turbine exhaust gas, when the speed reaches the turbocharger work (ie the turbine rotating at 100,000 rpm per minute) turbochargers before compressing the air around the engine intake air increases, improve engine power.
     At this point, we need in the intake duct installation of a pressure thermostatic valve device to remove the pipe from the intake of excess high-pressure turbo compressed air. In fact the pressure safety gas valve is a valve installed on the intake pipe for controlling the supercharging pressure. Opening and closing of the Gas Top Burner Valve is controlled by the ECU (electronic control unit) operated solenoid. ECU will be based on high and low pressure turbine outlet supercharged to make judgments, once the pressure exceeds a Gas Control Valve, will be on the electromagnetic coil is energized or de-energized control to open or close the Oven Safety Gas Valves.
     When the pressure pilot valves is closed to ensure that there is sufficient intake pipe inlet pressure as the basis, when the Manual Gas Valves is open can vent excess gas into the atmosphere, reducing the pressure inside the inlet to protect the engine air intake pipe. So we hear the modified car "ci, ci" sound is relief at the sound of the exhaust pressure Range Dual Safety Valves.