Hi Yvon,  I have attached a graph to help explain the problem.  In a
nutshell: With a narrow band sensor ( blue lines ), you can really only tell
for certain whether you are rich or lean, but not by how much. If you look
at the graph, you can see that for a narrow band sensor, the 12.5:1 AFR
required for maximum power can give O2 voltage from 0.8 to 0.95 (depending
on exhaust gas temperature), yet this same range of O2 voltages can indicate
mixtures from 10:1 to 14.5:1.  On the lean side it is a bit better but not
much, the resolution is about one tenth of a volt.

The graph also shows a wide band sensor ( red line ) with a wide-band
sensor, 12.5:1 corresponds to 2.08 volts, and 2.08 volts means 12.5:1. Thus
there is no ambiguity over AFR and voltages. We can measure any mixture in
the range we are likely to use, from full power through to maximum economy.
M

I would not read too much into the data you get from your Cyberdyne other
then rich or lean, how much lean or rich is a guess.  If you want an
accurate reading instrument for piece of mind check out
http://www.diy-wb.com/.  Otherwise if your engine is running smoothly and
egt is normal you will be fine.

Does the Holley Pro Charger use an oxygen sensor?

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On
Behalf Of Géraldine Berger & Yvon Cournoyer
Sent: Saturday, June 04, 2005 7:17 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: BAR GRAPH AIR/FUEL GAUGE


Hi Ian, I am flying with a Holley Pro-Jection two barrels fuel injection
system and a homemade intake manifold.
Yvon.

----- Original Message -----
From: "Ian Dewhirst" <ianddsl@magma.ca>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, June 04, 2005 5:49 PM
Subject: [FlyRotary] Re: BAR GRAPH AIR/FUEL GAUGE

Hi Yvon, what type of fuel system are you using? -- Ian


-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]On
Behalf Of Géraldine Berger & Yvon Cournoyer
Sent: Saturday, June 04, 2005 5:37 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] BAR GRAPH AIR/FUEL GAUGE


  I fly a Zenair Zenith 200 with a l986 13B.  I have installed a
Cyberdyne Instruments bar graph air/fuel gauge (P/N 7009). The O2
sensor
is located ~31 inches from the exhaust ports. The O2 sensor is not a
Cyberdyne Instruments part. It is an aftermarket universal single wire
sensor. The readings of the air/fuel gauge are baffling me. At idle of
1100  rpm and MP of 14.1-14.2 inches/mercury, the air/fuel gauge shows
a
rich condition of ~12.7:1. That is where the engine runs best at idle.
At full power static of 5200-5250 rpm and MP of ambient (~30
inches/mercury), the air/fuel gauge reads rich ~13.2:1. However, when
I
retard the throttle to 3000-3500  rpm, at a MP of 17.0-17.1
inches/mercury, then the air/fuel gauge reads lean at ~16.0:1. The
engine runs quite evenly at all power settings but I wonder if the
variations in fuel mixture are normal and safe?
Yvon.