Terrible Tom <silvereightynine@aol.com> wrote:
> Refresh my memory here... the higher the number value that the MAP
> reports - the more vacuum? And the lower the value - the closer the
> manifold is to external air pressure levels? (meaning less negative vacuum)
> Right?
Its the opposite - the higher the number reported by the MAP, the
less the vacuum. Remember, the MAP is a pressure sensor and is
reading pressure. The higher the number, the higher the pressure.
The vacuum will be inversely proportional to the pressure, so the
higher the MAP reading, the lower the vacuum (i.e. the vacuum is
moving towards zero), and the lower the MAP reading, the higher the
vacuum (the vacuum is moving away from zero).
This is why, when the engine isn't running, the MAP will report
something like 29"; that is the barometric pressure. When the engine
starts and a vacuum is created inside the intake manifold, the MAP
reading goes down because the engine vacuum is offsetting some of the
ambient barometric pressure.
--
-Jon-
.- Jon Steiger -- jon@dakota-truck.net or jon@jonsteiger.com -.
| '96 Kolb Firefly, '96 Suzuki Intruder, Miscellaneous Mopars |
`-------------------------------- http://www.jonsteiger.com --'
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