A perfect vacuum is 0 psi.
14.7 psi is what we breath at sea level.
Cars idle somewhere between 0 and 14.7psi, I think like around 5-9psi
absolute.

Something that confuses the issue is gauge pressure.  As suggested below,
opening the throttle will yield 0psi, but that should be 0 psi gauge
pressure, or 14.7 psi absolute pressure.  Depends on the frame of reference.

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Larry Alofs
Sent: Thursday, May 21, 2009 11:51 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: 2.1l vacuum readings?

17-21 sounds like a lot.  I thought that a perfect vacuum was about
14.7 psi.   :-)
  Maybe you're thinking inches of mercury?

Larry A.

On Thu, May 21, 2009 at 9:41 PM, Jake de Villiers
<crescentbeachguitar@gmail.com> wrote:
> Do you mean at idle? 17 - 21 psi I would think, like every other motor.
>
> You'll get zero when you open the throttle, that's okay.
>
> On Thu, May 21, 2009 at 4:43 PM, David Beierl <dbeierl@attglobal.net>
wrote:
>
>> Can someone remind me what sort of manifold pressure (vacuum)
>> readings I should be seeing on a 2.1l MV engine?