scudderfish
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| posted on 28/2/10 at 08:47 PM |
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5 wire lambda sensor positioning
I assume my lambda sensor has a built in heater given the number of wires sticking out of it. Does this mean I can up it in my exhaust pipe further
away from the engine? The easiest place for me to fit it is not far from my rear axle.
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DRC INDY 7
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| posted on 28/2/10 at 08:52 PM |
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It really needs to be on the down pipe
temp will be too low at the back even with heater built in
or in your case were the 2 down pipes join
The probe
The sensor element is a ceramic cylinder plated inside and out with porous platinum electrodes; the whole assembly is protected by a metal gauze. It
operates by measuring the difference in oxygen between the exhaust gas and the external air, and generates a voltage or changes its resistance
depending on the difference between the two.
The sensors only work effectively when heated to approximately 316 °C (600 °F), so most newer lambda probes have heating elements encased in the
ceramic that bring the ceramic tip up to temperature quickly. Older probes, without heating elements, would eventually be heated by the exhaust, but
there is a time lag between when the engine is started and when the components in the exhaust system come to a thermal equilibrium. This lag is due to
the engine, oil, coolant, and other components' absorption of heat from the exhaust gases. The exhaust gases heat these other components,
causing the gases to drop below the probe's operating temperature and therefore heat the probe slowly. The length of time required for the
exhaust gases to bring the probe to temperature depend on the temperature of the ambient air and the geometry of the exhaust system. Without a heater,
the process may take several minutes. There are pollution problems that are attributed to this slow start-up process, including a similar problem with
the working temperature of a catalytic converter.
The probe typically has four wires attached to it: two for the lambda output, and two for the heater power, although some automakers use a common
ground for the sensor element and heaters, resulting in three wires. Earlier non-electrically-heated sensors had one or two wires.
Location of the probe in a system
The probe is typically screwed into a threaded hole in the exhaust system, located after the branch manifold of the exhaust system combines, and
before the catalytic converter. New vehicles are required to have a sensor before and after the exhaust catalyst to meet U.S. regulations requiring
that all emissions components be monitored for failure. Pre and post-catalyst signals are monitored to determine catalyst efficiency. Additionally,
some catalyst systems require brief cycles of lean (oxygen-containing) gas to load the catalyst and promote additional oxidation reduction of
undesirable exhaust components.
[Edited on 2/28/2010 by DRC INDY 7]
[Edited on 2/28/2010 by DRC INDY 7]
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Puddle Dodgers Club
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MikeRJ
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| posted on 28/2/10 at 10:11 PM |
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A five wire sensor will be a wideband sensor. Rear axle will be too far though, not only will the exhaust be too cool it will take longer to reach
the sensor so you could cause control loop problems.
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scudderfish
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| posted on 5/3/10 at 12:53 PM |
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Ok, thanks for the info.
Regards,
Dave
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