What is the function of the blow-off valve in a turbocharged engine?
1 Answers
The function of the blow-off valve is to prevent the turbo pressure from becoming too high, and it also helps avoid excessive pressure in the intake manifold. If the turbo pressure is too high, it can lead to turbocharger failure. Similarly, if the pressure in the intake manifold is too high, it can compromise sealing performance. Here are the relevant details: 1. Turbocharged engines in cars typically have two blow-off valves—one in the intake system and another on the turbocharger itself. The intake system's blow-off valve activates when the driver releases the throttle pedal. When the throttle pedal is released, the throttle valve remains at a very low opening. However, the turbocharger continues to compress air and deliver it to the intake manifold. At this point, the engine does not require as much air, and the throttle valve opening has already decreased. This leads to a large volume of air accumulating in the intake manifold, increasing the pressure inside. If the pressure in the intake manifold becomes too high, it can cause the intake manifold to rupture. Therefore, the blow-off valve is necessary—after releasing the throttle pedal, it can vent some of the air from the intake manifold, preventing excessive pressure buildup. 2. When the engine speed is too high, the turbocharger's speed also increases, and the turbo pressure rises. If the turbo pressure becomes too high, it can cause the turbocharger to fail. At very high engine speeds, the turbo's blow-off valve opens, allowing exhaust gases to bypass the turbocharger and enter the exhaust manifold directly. This prevents the turbo pressure from continuing to rise.
