You are correct, I was sloppy. It must have been an SE to have that kind of gauge panel.

I did a crude calibration with the "Economy" gauge using a large vacuum gauge I just bought and my Mityvac. The right hand stop (in the red zone) of the Economy gauge is very close to full atmospheric pressure (0" Hg vacuum) as would be expected. All the way to the left stop in the black turns out to be 14.5" Hg or about half an atmosphere.

Since atmospheric pressure at sea level is about 14.7 psi (1 bar), the range of the gauge is equivalent to half of that, or about 7 psi, maybe a bit more. Thus if you pry off the pointer and move it from the right end of the scale to the left end, you will end up with a range of 0 to 7 psi. By applying 5 psi to the gauge, calling that "zero," and setting the pointer at that point, you will get Sixto's range of 5 to 12 psi. I wish it were possible to increase the range to 0-15 psi but I don't think the gearing of the Economy gauge will allow it.

I'll do some more experiments later and report.

Jeremy

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
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"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970