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Date: Sat, 04 Jun 2005 23:09:03 -0400
From: =?iso-8859-1?Q?G=E9raldine_Berger_&_Yvon_Cournoyer?=
 <geryvon@videotron.ca>
Subject: Re: [FlyRotary] Re: BAR GRAPH AIR/FUEL GAUGE
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
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 <geryvon@videotron.ca>
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Thank you Ian, very clear and satisfactory explanation.
To answer your last question: the system I purchased and use on my 
Zenith monitors three signals: engine coolant temperature, throttle 
position and engine speed. I found out recently that Holley now offers a 
rich/lean indicator for use with their fuel injection systems. I am 
requesting more info from them about this indicator, but its name 
suggests a narrow band sensor.
Yvon

----- Original Message ----- 
From: "Ian Dewhirst" <ianddsl@magma.ca>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Saturday, June 04, 2005 9:39 PM
Subject: [FlyRotary] Re: BAR GRAPH AIR/FUEL GAUGE


> 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.
>