I've been poking around the RX-8 forum, and there are some interesting people on there with some interesting ideas. I'm glad I'm not on that forum, I'd have no more free time left..

 

Okay... Wastegates are set to a particular spring pressure. 17psi is 17psi at sea level or in Denver, no? So, if a turbo has the room(rpm) to move the extra air it takes to make that 17psi at an elevation of 4k ft., it will, yes? There foremaking the same power?

 

One side of the diaphragm is referenced to boost pressure, and the other side isn't sealed at all, so it's referenced to ambient pressure. The only thing that matters is the pressure difference between one side of the diaphragm and the other, and that pressure difference what makes the force on the spring. So the wastegate will always open at 17 psi above ambient pressure no matter where you are.

As far as making the same power, you won't make the same power with 17 psi here in Denver that you would at sea level. You'll have 17 psi either way, but that's 17 psi on top of the ambient pressure that you're getting into the engine. Lower ambient pressure in Denver means it might be 12.23 psi ambient + 17 psi boost instead of 14.7 psi + 17 psi boost at sea level. That's the difference. The difference between the ambient pressure is the extra boost you would need to make the same power in Denver. So 14.7 (sea level) - 12.23 (Denver) is 2.47 psi, which is the extra boost you would need to make in Denver for the same power. SO that would be 17 psi + 2.47 = 19.47 psi boost in Denver to make the same power as 17 psi at sea level. There are some other minor factors of course, and the relationship between altitude, air density, and power output isn't exactly linear like that, but you get my meaning. In other words, you have to turn the boost up to compensate for higher altitude.

 

Final Cliffnote: