[Camaro1973]

Originally Posted by Idaho2018GTPremium

I think you are thinking of something else when it comes to "boost". The absolute manifold pressure will be lower because the lower barometric pressure is a lower starting point. That's not the boost pressure I was talking about. I was specifically referring to the pressure increase across the blower; what most people refer to as "boost" and engineers might call gauge pressure downstream of a blower. It inversely is the pressure loss across the system (engine and exhaust). Its lower at high elevations since the mass airflow rate is lower, and thus, there's less restriction.

If you can spin the blower faster to get the mass airflow back to what it would be at a lower elevation, then yes, since the mass airflow is equal, boost would go back up, and the engine would theoretically make the same power (that requires some assumptions, though, e.g., similar blower eff.).

And as far as ambient temperature, I wasn't implying that it is only applicable at high elevations, it is of course applicable anywhere. I was pointing out where supercharging loses more than a naturally aspirated engine (due to the higher charge air temps adversely affecting timing).

Uhh. I think your confused. The pressure across the blower is lower because the barometric pressure is lower. Bring up the barometric pressure and boost goes up it’s very simple.

Which is why these guys in Denver close to fuel system limits can’t run at sea level because they’ll make many more lbs of boost and be out of fuel.