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JCW A/F Gauge Report
Just got one of those $36 A/F ratio gauge from JC Whitney and this is what
I observed so far: The gauge is 2 1/16" in diameter, so will mount in
standard faceplate. A "U" shaped bar is used to hold it tight in the rear.
A National LM3914 dot/bar display driver does the A/D conversion. The
display is a vertical bar consisting of 10 multi-colored LEDs, with green
as the middle two, surrounded by 2 pairs of yellow LEDs, and finally 2
pairs of red LEDs at each end. In addition 3 red LEDs shining through
transparent overlays displaying the legends "RICH", "LEAN", and "AIR FUEL".
These all shine thru a smoked plastic faceplate. LED brightness is fixed.
Its manufactured by Intellitronix Corp. in Lakewood, OH. Comes with
installation instructions and a warning that this gauge "only displays a
rich or lean indication" and is "physically impossible to measure an exact
air/fuel ratio with a standard oxygen sensor."
Gauge works as a 0-1 V meter in 0.1 volt steps and is accurate. The LM3914
is set for bar mode, so all LEDs light as voltage increases. The display
will show 2 red, 2 yellow and 1 green LED to indicate "lambda" (0.5V or
14.7:1 A/F ratio).
Picture of display in .jpg format (133K) is available upon request.
Tony Lum 1987 5000CS Turbo Quattro
Berkeley, California, U.S.A. 1985 4000CS Quattro
Audi Owner/Driver/Mechanic by Necessity ;^) 1980 5000S Sedan
QCUSA Member #6885 1987.5 Coupe GT