Article on The Internet Mini Encyclopædia
Lambda sensors are an essential part of the feedback mechanism used to regulate fueling in fuel injection systems, however as a function of the lambda sensor is to determine air-fuel ratio (AFR) , lambda sensors can be used on non fuel injected cars (running unleaded fuel) to display information on state of tune.
Simple lambda sensors are single wire and in the presence of exhaust gases will return a small voltage roughly proportional to the Air/Fuel Ratio or Lambda ( the true relationship is very non linear) - these simple NARROW BAND lambda sensors are of little real value as a tuning aid and typically rely on being located in the exhaust manifold or close to it to maintain their required high working temperatures, they are stand alone and do not require a control circuit to regulate their working temperature.
The more complex multiwire WIDE BAND lambda sensors typically are self-heated to around 750c via a control circuit so other than avoiding locations at the end of exhaust systems (where outside air could be entrained) they can be placed to suit the associated wiring rather than relying on a hot location that could be less than ideal for the wires.
There are a number of retrofit lambda sensor control and AFR/Lambda output modules, many of which have evolved with the development of DIY fuel injection systems, many of these can modules can also output the necessary signals required for the original NARROW BAND lambda control systemso they can operate to only monitor AFR using a WIDEBAND sensor but to feed the original injection system with the voltage it needs.
My own use of these retro fit systems resulted from an interest in monitoring the state of tune of my HIF6 K&N Torque Ram 37x29 head equipped 1330 Mini, since rolling road tuning ( at Lambs Dynotune / Lambs Garage in Clowne Derbyshire) the setup took 6 hours as the torque ram ended up needing the carb to use a HS6 dashpot and two springs!!!!
The original carb body sadly had to be replaced after 10 years of standing full of unleaded ( the works got gummed up) leading me to refit the modified needle and jet in another HIF6 carb body - BUT how could I check that this did not lose the rolling road setup.... I had to check AFR was good throughout the throttle range under load WITHOUT a rolling road...... then JAW came along!
I sourced a self heating lambda sensor ( a BOSCH 17053 ) from the USA from Rockauto.com and linked it to an inexpensive ( the least expensive in fact) JAW ( Just Another Wideband) controller ( http://www.14point7.com/JAW/JAW.htm ) using connectors from my local VW garage ( then got a longer cable pre manufactured from VEMS http://shop.vems.hu/catalog/index.php?cPath=1 ) and a lambda mounting collar from http://www.Trigger-wheels.com - my lambda sensor is mounted between the boxes of my RC-40 twinbox system with the cables from the lambda emerging through the central tunnel behind my seat
The JAW is setup using a laptop computer via a COM cable or COM to USB cable/adaptor ( can be problematical this way if you have a clunky USB adaptor BUT you may not have a choice if your laptop is USB only) and the JAW module can output to the JAW supplied LED displays to view AFR / LAMBDA etc etc or to drive third party displays using the configurable VOuts ( see the JAW website)
The JAW can work as a datalogger as well as a clear output of the AFR if you have it running while driving.... tweak the jet height and you can then check the AFR effect.... JAW can integrate with rev counters and exhaust gas temperature sensors too....
Can you detect the fact I am VERY impressed with what JAW can do for so little cash..... too damn right I am!!!!
LAMBDA SENSORS ARE SENSITIVE!: Wikipedia says: Leaded gasoline contaminates the oxygen sensors and catalytic converters. Most oxygen sensors are rated for some service life in the presence of leaded gasoline but sensor life will be shortened to as little as 15,000 miles depending on the lead concentration. Lead-damaged sensors typically have their tips discolored light rusty. Another common cause of premature failure of lambda probes is contamination of fuel with silicones (used in some sealings and greases) or silicates (used as corrosion inhibitors in some antifreezes). In this case, the deposits on the sensor are colored between shiny white and grainy light gray. Leaks of oil into the engine may cover the probe tip with an oily black deposit, with associated loss of response. An overly rich mixture causes buildup of black powdery deposit on the probe. This may be caused by failure of the probe itself, or by a problem elsewhere in the fuel rationing system. Applying an external voltage to the zirconia sensors, e.g. by checking them with some types of ohmmeter, may damage them. If your headgasket is blowing it won't be good for any lambda sensor if oil or antifreeze is getting into the bores!
Updated September 28, 2008
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