Pop-off Valve: Usefulness and Purpose

Hello,

I somehow recall that there was a discussion before about the usefulness or lack thereof of pop-off valves. I can't find that thread using the search function .
Perhaps it hasn't been fully explored yet.
Okay, let's start with the terminology: I'm envisioning installing a valve in the charge air duct. This valve should release "excessive pressure" so quickly that the control system of the variable turbine geometry (VTG) doesn't even need to adjust the guide vanes to minimize pressure buildup.
Is that the function of a pressure relief valve?

Normally, with increased boost pressure and increased fuel injection, you experience such strong pressure surges that the VTG (variable turbine geometry) control system initially produces "undershoots," and it takes almost 5 seconds to maintain a constant boost pressure.

My boost pressure has been increased to 1.1 bar using a diode solution.
If one were to install a valve that opens at 1.2 bar, wouldn't that valve then:
1) Reduce pressure peaks, thereby minimizing axial torque on the impeller shaft (leading to a longer lifespan).
2) Can the control loop of the VTG (Variable Turbine Geometry) reach the holding pressure of 1.1 bar more quickly?

Thank you for your responses.
Georg G.[/b]

Pop-off valves, in gasoline engines which have a throttle valve, are designed to maintain the airflow and thus the turbocharger's speed even when the throttle is briefly released, so that power can be quickly restored when the throttle is opened again.
While adjusting the timing might help with over-revving, there's a risk that it could significantly increase soot emissions and cause the turbocharger to fail due to excessive speeds.

Hello Christian,

Okay... Then "Pop-Off" is probably the name of a different construction site .
How exactly does maintaining the mass airflow work? Is pressure from the intercooler system applied to the turbine's intake side to keep it at a certain speed (since the exhaust gases are no longer present when the throttle is closed)?

Thank you for the responses.
Georg.

Hi,
At Audi, the air is circulated as standard. However, some people convert it to exhaust air circulation due to the noise.

@Georg_G

It's essentially about preventing the turbocharger from being braked too aggressively (i.e., slamming into a wall). Now, imagine that during a gear change, the throttle suddenly closes (of course, no power is needed at that moment). The turbocharger would slam into a wall and be braked abruptly. This isn't particularly good for its lifespan. However, if you release the pressure, the turbocharger can gradually spool down (like in a TDI engine). After the gear change, the turbocharger can quickly return to its operating speed and provide boost again.

Best regards, WarLord.

Hello Warlord.

Thank you for the explanation; now I can understand it a little better.

Georg.