Blow off Valve is a kind of valve developed to minimize turbo lag in turbochargers. This system is valid for vehicles with turbo engines and is produced to reduce the activation time of the turbo rather than performance and to use the turbo in a healthy way.
The job of the turbo is to provide compressed air flow to the engine and it does its job as long as you step on the gas. When you cut off the throttle, the turbo turbines still continue to rotate with the air flow. However, since the air passing the turbines cannot move further, it starts to flow in the opposite direction and causes the turbines to rotate in the opposite direction. In the meantime, when you press the gas again, the turbines that turn to the opposite side stop to start operating again, and this time they turn to the other side. In other words, if the turbines turn from left to right while pressing the gas, they will turn from right to left when you release the gas. This will delay the activation of the turbo and damage the turbines. Blow-Off, which was developed to prevent this, ensures that the air that causes the turbo turbines to turn to the opposite side is thrown out when you cut the gas. So the turbo responds more quickly when you step on the gas. It also creates a sporty sound during throwing.