jackb_ms Posted March 22, 2004 Share Posted March 22, 2004 I would like to know if someone can enlighten me on the role of the lambda probe. What can happen if mine is faulty? Jack Emily, The Very Yellow 21 Link to comment Share on other sites More sharing options...
Tony C Posted March 22, 2004 Share Posted March 22, 2004 Have a look here - bet you wish you hadn't asked now 😬 BRG Summertime Brooklands SV 😬 It is only with the heart that one can see rightly; what is essential is invisible to the eye. (Antoine de Saint-Exupery) Link to comment Share on other sites More sharing options...
Roger King Posted March 22, 2004 Share Posted March 22, 2004 Put simply, it measures the oxygen level in the exhaust. This information tells the ECU what the fuel/air ratio is and then allows it to alter it to the correct level for the proper operation of the catalytic converter. The catalytic converter needs a stoichiometric fuel/air ratio. All this means is that there has to be exactly the right amount of air fully to burn the fuel put through the engine - not too much, not too little. This ratio has to be controlled very precisely for the catalytic converter to work. Link to comment Share on other sites More sharing options...
jackb_ms Posted March 22, 2004 Author Share Posted March 22, 2004 Thank You Roger So if I have removed my cat the probe is now redundant. Or it's not as simple? Jack Emily, The Very Yellow 21 Link to comment Share on other sites More sharing options...
Tony Martyr Posted March 23, 2004 Share Posted March 23, 2004 Jack, No it is not entirely redundant. If you remove the CAT you may not and need not remove or disarm the closed loop control of Lambda ratio which is part of your ECU control strategy. If you change your ECU or its map so that you have not got closed loop control of lambda even then the probe is not redundant because it is a very useful tool in the performance mapping process. Without knowing the air/fuel ratio mapping is a far more difficult process and, in my view, much less trustworthy. Link to comment Share on other sites More sharing options...
Bob Corb Posted March 23, 2004 Share Posted March 23, 2004 If you have an OEM ECU i.e. rover Mems then I'd leave it in. The ECU uses the lambda sensor as an input to an adaptive library which keeps the mixture spot on (but only at part load). Taking it out will cause a fault code which may in turn lead to strange phenomenonononon...(?) BC Link to comment Share on other sites More sharing options...
frankyknuckles Posted March 23, 2004 Share Posted March 23, 2004 how are things changed if you keep the cat but move the probe to the 4th collector instead of it beind next to the cat? I presume it means the measurement is only for one cylinder and not the output from all 4? Build Diary Link to comment Share on other sites More sharing options...
charlie_pank Posted March 23, 2004 Share Posted March 23, 2004 Franky, you're right and frankly, I've never understood why people would do such a thing! Link to comment Share on other sites More sharing options...
frankyknuckles Posted March 23, 2004 Share Posted March 23, 2004 but when a de-cat pipe is fitted, the lambda probe goes in the 4th collector (I think) so there can't be many down sides can there Build Diary Link to comment Share on other sites More sharing options...
charlie_pank Posted March 23, 2004 Share Posted March 23, 2004 Cat is nowhere near lambda, so why does it get relegated to 4th cylinder - surely all you need is a longer cable? Link to comment Share on other sites More sharing options...
Bob Corb Posted March 23, 2004 Share Posted March 23, 2004 If you've got no cat then the lambda sensor is almost superfluous. You just keep it to stop the ECU seeing a fault. Therefore instead of having it on show it can be tucked away inside on runner 4. In an ideal world it would work just as well in runner 4 as it does downstream of the collector but in reality the fuel mixture varies from cylinder to cylinder so for best emisions you want the cat to get an average AFR that is stoichiometric (i.e. = 14.5) even though some sylinders run richer and some leaner than the average. BC Link to comment Share on other sites More sharing options...
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