Quote:
Originally Posted by Needsdecaf
It's not incorrect. You're both right, but you're talking about two different things.
1.0 Bar is 14.5 psi, or normal atmospheric pressure. But "gauge" pressure measures what you are speaking of: pressure above the surrounding atmosphere. Boost pressures for engines are typically given in "gauge" pressure not "absolute". So you are correct in that the actual pressure in the intake tract is 2.5 bar, but "gauge" pressure is 1.5 bar.
Good reading here including a handy diagram, which I like:
http://www.engineeringtoolbox.com/pressure-d_587.html
By the way, not sure why everyone is so hung up about the bar thing. It's just another system of pressure measurement. Certainly people are familiar with converting N-M to ft-lbs for torque and kW to HP for power, no? |
I know.....
That is why I originally stated that 1.5 bar might only equate to 8 psi.
BMW specified on page 1 that their 1.5 bar measurement was absolute pressure (which includes atmospheric), not gauge.
Gauge pressure is signified by a ‘g’ after the pressure unit e.g. 30 psi g, this indicates that the pressure measured is the total pressure minus atmospheric pressure.
Absolute includes atmospheric pressure, so you have to subtract 14.7 psi from the 22.
Given that the N54 platform only pushes 9 psi, I would be surprised if BMW came out with an engine that pushes 22 psi stock.
