[Diy_efi] Lead fuel compaible O2 sensor

[dh at busb.com]

The reason temperature isn't used is that it is a multi-order curve.  As the
mixture is changed the exhaust temperature will move from a low value to a
high value and back to a lower value.  This is a difficult case for a closed
loop controller such as a computer.  If the wrong slope is assumed the
engine may be destroyed before the error is detected.  Exhaust temperature
is also affected by many variables other than mixture.  Cam overlap will
cause wide variations in exhaust temperature with all other factors being
equal, therefore lash variations will cause changes, resulting in poor
repeatablity.  An occasional miss will also hose up the works, but not in a
repeatable manner.

dh



----- Original Message ----- 
From: "gary" <gas- at charter.net>
To: <diy_efi at diy-efi.org>
Sent: Sunday, July 03, 2005 10:01 AM
Subject: Re: [Diy_efi] Lead fuel compaible O2 sensor


> AFAIC, (not part of any race team) in today's race environment,
> any race team attempting to determine AFR by means of EGT is
> either not very serious about getting accurate measurements, or
> has the time/budget to do necessary engine testing.  This would
> exclude true pro race teams, as they accept the limited life of
> WBO2 sensors when exposed to lead.  There IS a life, it is just
> not as long.  We're not talking one sensor destroyed at a time
> either, but 8 (8 cylinders) sensors at a time.  Not stating they
> do not employ services of EGT as well, but their use would be
> in a role of supplementing O2 sensors, not replacing them. On
> their own, there are just too many variables that affect EGT.
>
> Using the Bosch spec for the expected life span (of an a particular
> WB sensor), with the use of unleaded fuel in an OEM application,
> of 60,000 mi/97,000  km, as a gauge, comparos can be made.
>
> Adding .15 g/ltr. of lead reduces the life to 60,000 km.
> Adding .6 g/ltr. of lead reduces the life to 20,000 km.
> I understand 100LL AVGAS has a lead content of .56 g/l.
>
> We can put this length (mi/km) lifespan in perspective, by converting
> it to time.  Typical long term average speed of a vehicle in regular
> (street) use would be ~ 50 km/hr.  Using .6 g/l lead as an example,
> avg. lifespan would be 400 hours.  What would be the avg. speed
> for any given race vehicle application/class?  Figure accordingly.
>
> My info (obtained from WB sensor forum discussion), state lead
> concentration varies from 1.12 -1.6 g/l in common/popular leaded
> race fuels used.  Degree of deterioration of sensors exposed to
> lead, is not 'linear'.  IOW, doubling the amount of lead in the fuel,
> will not shorten the sensor life by ?.
>
> Rest assured, WB O2 sensors are DEFINITELY used for race
> vehicle tuning.  Again, depends on how serious or knowledgeable
> any given team is.
>
> GAS
>
>
> ----- Original Message ----- 
> From: "Phillip Kuhn" <pmkls1 at yahoo.com>
> To: <donsauman at cythera.net>; <diy_efi at diy-efi.org>
> Sent: Saturday, July 02, 2005 10:26 PM
> Subject: Re: [Diy_efi] Lead fuel compaible O2 sensor
>
>
> > As far as I know there is no such thing, ususally on cars
> > that run leaded fuel, such as race cars, they will use
> > exhaust temp sensors to monitor a/f ratios.  Somebody
> > else may know more about that that me though....
>
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