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Re: More than you need to know about gauges

Sorry for the long delay, Gisli.

Gisli Ottarsson wrote:
> Wow!  Thanks for the generous info, Igor.

> Two question, for clarification, if I may:
> 1) You cite the following specs:
>     VDO  150 921 -30" Hg to +25psi and -1 bar to +1.5 bar
>    I presume that the +1.5 bar is relative to atmospheric pressure,
>    i.e., that it corresponds to a 2.5 bar reading of the in-dash
>    gauge. 


> The reason I ask is that I had conviced myself that a 20psi
>    gauge would be inadequate but if this corresponds to 1 Atm + 20 psi
>    then this is plenty (for my application).

Correct. That's what I had in my '89 200TQ. Ran it at 17psi. At 20psi
the engine would start detonating (too lean a mixture - very dangerous).

> 2) In your experience, when a gauge is advertised having a 52mm dia,
>    is this the diameter of the outer edges of the frame or is this the
>    size of the mounting hole?

It's the mounting hole DIA.

Igor Kessel
Two turbo quattros.