What is the sound like air being released when the car's accelerator is released?
3 Answers
Releasing the accelerator and hearing a sound like air being released is the sound of the pressure relief valve working. The following explains the reasons: 1. Turbocharger working principle: When the turbocharger starts working as the accelerator is pressed, it compresses a large amount of air and pushes it into the engine combustion chamber through the throttle valve. When the driver releases the accelerator pedal, the throttle valve closes. However, the turbocharger's blades do not stop working immediately. At this time, there is still residual compressed air in the intake pipe between the turbocharger and the throttle valve. If this air is not discharged in time, the strong pressure can cause damage to the throttle valve and turbocharger blades. 2. Function of the pressure relief valve: The valve of the pressure relief valve will release the residual compressed air in the pipe in time when it detects that the air pressure in the intake pipe is too high, thereby protecting the throttle valve and turbocharger blades. It also reduces the occurrence of turbo lag, making the engine work more smoothly. The sound of air being released that you hear is the 'noise' produced when the pressure relief valve discharges the compressed air.
Hey, my car used to make a hissing sound when I let off the throttle too, which was pretty annoying. The most common cause is the turbocharger's blow-off valve doing its job - when you accelerate and then release the throttle, the valve opens to release excess air, making that 'psssh' sound. This is usually normal, especially in modified cars or during aggressive driving. But if the sound becomes particularly sharp or frequent, it could mean the valve is stuck, there's a loose intake hose leaking air, or there's a small hole in the exhaust system. I'd recommend first checking under the hood to inspect the turbo-related pipes for any cracks or loose connections. If the sound comes with increased fuel consumption or power loss, don't hesitate - get it diagnosed at a repair shop right away to prevent small issues from worsening and affecting driving safety.
As a veteran auto mechanic with years of experience, I've handled numerous cases like this. The hissing sound when releasing the throttle is mostly caused by the pressure relief mechanism in the turbocharging system. When engine load decreases, the valve releases pressure creating the noise, which isn't concerning during normal driving. Other possible causes include malfunctioning bypass valves in the intake system, leaks in vacuum hoses, or abnormal PCV valves allowing air escape. Damaged exhaust manifold gaskets may also produce similar hissing sounds during deceleration. I recommend using a multimeter to check hose sealing integrity. If the sound is abnormal or accompanied by other issues like engine vibration, seek professional diagnostics. Neglecting this could lead to more serious engine problems.
