370Z's and E85?

T_K

Because a boost gauge is a relative pressure gauge. It measures the difference between the pressurized air and atmospheric pressure.

TopgunZ

Doesn't it measure vacuum pressure and forced pressure in the manifold?

phunk

Yes but it measure relative to the atmosphere pressure. Atmospheric pressure is zero on a boost/vacuum gauge, at any altitude. So you have to run 2.6psi more boost on the gauge to get the same air pressure in your manifold as the same exact car at sea level. So if you drove down to sea level. And ran the same boost gauge pressure, you will get 2.6psi more manifold pressure than you did in Denver, and make more power (and lean out if you're in a car without MAF sensors or absolute MAP reference, or if you don't have enough fuel for the extra HP)

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