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is an O2 sensor the same as a lamba sensor
mad-butcher - 26/4/10 at 06:47 PM

As title
would be gratefull if someone could explain

tony

FrankP - 26/4/10 at 06:52 PM

Yes
there are two types:
Narrow band - normally 2 wires
Wide band - normally 5 wires more sophisticated can be connected to gauges and ecu to run afr....

Cheers

Frank

matt_claydon - 26/4/10 at 06:53 PM

Yes.

Lambda is the ratio between your actual AFR and the stochiometric afr (14.7). If you are actually running at 14.7:1 then your lambda is 1 (which results in theoretically perfect combustion). The sensor does this by measuring the amount of oxygen in the exhaust gas (hence O2 sensor).

If there is oxygen in the exhaust gas, the sensor gives off 1 volt. If there is no oxygen then it gives off no voltage. By ensuring the sensor is constantly 'flickering' between 0 and 1 volts, the ECU knows your are at 14.7:1 AFR.

[Edited on 26/4/10 by matt_claydon]

britishtrident - 26/4/10 at 07:36 PM

quote:
Originally posted by FrankP
Yes
there are two types:
Narrow band - normally 2 wires
Wide band - normally 5 wires more sophisticated can be connected to gauges and ecu to run afr....

Cheers

Frank


Two wire lambda sensors are very uncommon certainly no modern car has one.

Narrow band oxygen sensors can have one, two three or four wires --- most cars sold in the UK in the last 15 years have 4 wire narrow band Zirconia Heated Oxygen Sensors. In a 4 wire sensor the wires are Sensor output, sensor ground, heater 12v, heater ground. This type of sensor is often called a HEGO sensor (ie Heated Exhaust Gas Oxygen).
A Zirconia lambda sensor is actually a tiny fuel cell that produces a varying voltage (usually but not always 0 to 1v) depending on the oxygen content of the exhaust gas.

Wide band exhaust gas oxygen sensors work on an entirely different principal and the output signal is a tiny current through the sensor not voltage generated by the sensor.

All Lambda exhaust gas sensors are oxygen sensors but not all exhaust gas sensors are lambda sensors. Wide band sensors are a different technology lambda sensor.





[Edited on 26/4/10 by britishtrident]

britishtrident - 26/4/10 at 07:41 PM

quote:
Originally posted by matt_claydon
Yes.

Lambda is the ratio between your actual AFR and the stochiometric afr (14.7). If you are actually running at 14.7:1 then your lambda is 1 (which results in theoretically perfect combustion). The sensor does this by measuring the amount of oxygen in the exhaust gas (hence O2 sensor).

If there is oxygen in the exhaust gas, the sensor gives off 1 volt. If there is no oxygen then it gives off no voltage. By ensuring the sensor is constantly 'flickering' between 0 and 1 volts, the ECU knows your are at 14.7:1 AFR.

[Edited on 26/4/10 by matt_claydon]


Nicely put

britishtrident - 26/4/10 at 07:52 PM

Found these deep in my bookmarks
http://www.lambdapower.co.uk/TechNotes/technotes_index.asp

http://en.wikipedia.org/wiki/Oxygen_sensor

matt_gsxr - 26/4/10 at 10:45 PM

Regarding the wideband ones. One wierd thing is that although called oxygen sensors they don't actually measure the oxygen content.

If you think about it this is obvious, because how could they measure the difference in AFR between say 12 and 13? In each case there is no oxygen left in the exhaust.

They actually have the ability to determine how much oxygen would be needed to combust what is in the exhaust.

Damned clever stuff. The wikipedia reference explains this better than I can, and it doesn't actually matter.

Matt