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Turbo Pressure Limit Based On Atmospheric Pressure

Turbo Pressure Limit Based On Atmospheric Pressure
The turbo pressure is reduced as atmospheric pressure is reduced. This is to maintain the same relative pressure and prevent turbo overspeed. At higher elevation atmospheric pressure is less than at sea level. The difference between the pressure at the manifold and atmospheric pressure is called relative pressure. The turbo charger makes up for the difference in most circumstances. Here's a quick example.
 
0PSI atmospheric, 14PSI target: Difference 14PSI
-2PSI atmospheric,12PSI target: Difference 14PSI
 
If we were to still target 14PSI then it would end up with a 16PSI difference, which is more than the original intention. That is why this adjustment exists and is available.