I've decided to fit a mounting boss for a lambda sensor in my exhaust system, not because I need it - I've got carbs - but because I want to experiment. It also might come in useful when I go to the rolling road. I'll be making a plug to block it up until I'm ready to use it.

I just need to check a few things...

* The thread for the most common sensors is 18mm x 1.5mm I believe - is this right?

* Where is the best place to fit it? Obviously it should go on the final collector (or just after), but I've read somewhere that the bit on the outside needs a flow of fresh air - can I fit it within the bodywork, or have I got to fit it outside? I'd rather not have it too exposed.

cheers,
David

[Edited on 19/3/08 by David Jenkins]

Don't think there's any need for it to be exposed. It really wants to go as close to the engine as possible as they rely on the gas being very hot (not so important with a heated sensor but still the closer the better), so at the first point after all four pipes have merged is the right place.

You can buy lambda bosses (often with blanking plugs included), varying from about £4 to £8 depending on whether they are stainless or mild steel and whether you get a bung or not. Just search google or ebay for "lambda boss" and you'll get loads of hits.

If it's inconspicuous then you can just use a spark plug as a bung - they have the same thread. (You can also then do interesting flaming exhaust antics with some switches on the coil supply )

[Edited on 19/3/08 by matt_claydon]

lots of info on this site, ive used these guys, very helpful.

http://www.gendan.co.uk/

Another good link! Many thanks.

I've ordered a boss & plug off ebay - and found that it will be provided by a member of this forum! Not sure I should name him in case ChrisW accuses him of advertising so, for the sake of discussion, I'll just whisper it... Nick Skidmore.

[Edited on 20/3/08 by David Jenkins]

He's a paid up trader so he'll be alright

David , don't know if its any help but I put mine just before the connection to the silencer after the "collector" . Its fitted so that the sensor is horizontal with the leads going straight through the ally side panel . Decided to fit it that way as its less exposed . Managed to get ECU pretty close using a narrow band sensor and Emeralds soft ware . According to Emeralds Dave Walker it is possible to use a decent multimeter as a way of measuring emissions. If you want I will sort out his book for the info. HTH Mel

Ideally you should put the boss on the top of the pipe, but in any case it should be somewhere in the upper half (this is according to the Innovate manual). Apparently if the sensor is in the lower half then moisture can sit in it and damage the sensor. Not sure if this is a wideband only issue and in any case I've mounted mine at about 8 o'clock and had no trouble.

You can indeed easily just use a multimeter as a AFR gauge with a narrowband sensor. Just hook it up to read voltage on a scale of 0-1v - 0.5v output from the sensor is stochiometric and the meter will swing either side of that to show rich or lean. You will get about 0.2v when lean and 0.8v when rich. With a narrowband it's almost impossible to get anywhere between those extremes but when you've found the point that it switches rapidly between the two you know you are about right. An analogue meter would be best, digital might not update quick enough to give a meaningful reading.