Do external wastegates open up at an absolute pressure or gauge pressure? I'm here at 6000 feet, and when I'm boosting ~2.5psi (per my boost gauge), my standalone reads 0psi (100KPa)... I know that this is due to the difference in gauge pressure vs abolsute pressure in regards to my high elevation.

Which pressure will the wastegate open at? gauge or absolute?

This question will pertain to us high altitude people a little bit more...

 

since the stiffness of the spring never changes.... it will open at the absolute pressure it is set at... same at all altitudes.

what i mean is they set it up to boost 8 psi say at sea level it'll boost 8 psi regardless of altitude. because the 8 psi is a mechanically set property.

 

So, in that case... if it opens at 8psi at sea level, then what will my gauge read (up here at 6000 feet) when the same gate opens? Will it read 8 or greater (or less) than 8?