Lambda sensa stuff....
Turbo Mini Forums

Right to save hijacking the other thread currently running about this, i will start a new one....

There are a number of points about these that i am somewhat unclear on. i have sort of gone through the theory as i understand it, and would be extremly grateful if anyone could correct me where i am wrong......

It would seem from reading what has been said about these sensors that they are a very good idea, several people saying that they would not run a modified turbo without one. fair enough.

So, i understand that a lamba sensor measures the air fuel mixture and will tell you whether you are running rich or lean. This should (i presume) help you to see when you are about to melt your engine, right?

Modern cars have these sensors to control the ecu i gather? obviously this is not an criterea many of us on here are worried about, (i am well aware that several people are running fully mapable systems and fi, but most are running a dizzy and carbs i believe) so presumably as far as we are concerned, these are just for montiering purposes, and not to help as a running aid as such?

Wide band v narrow band? This goes completely over my head. can someone explain this too me???

Also what are the differences between the available kits? the Australian one (link in other thread - autoshop or something) works out at just under A$30, which by my reconing is about ?13 including shiping to the uk. now the link in the other thread is about US$150 plus shipping. now i know that the aussie one is a diy job, and the US one comes in a fancy case, but i assume there is some major differance? Then there is the kit being offered by someone from here? (appoligies, i have forgotten your name) Which one am i best going for?

Last question for now. Is a lambda sensor a lambda sensor, or is there more than one type? Im guessing from the wide-narrow thing that there are different types? so are these phsically a differnt size?

Hope somebody can help,

Pete

And on the 7th day........... God created turbochargers!

Pete,
Your generally correct in what your saying, for fi people the sensor can be wired into the ecu, to give further information re fuelling.
For carb guys, you can use as a realtime indicator of AFR ( Air fuel ratio) esp important when you have a modified motor as the fuel 'map' will be different and even more so when you have variable boost, as this will also affect fuelling.
I'm too a little in the dark about wide and norrow band, but as i understand it most fi cars have a pretty standard narrow band fitted. If we say a perfect mixture is 1, then a narrow band will go from 0.85 to 1.15.
These are used as I say in bearly all cars, as the fuel map is pre programmed accurately to start with, so the lamda is just to make sure all is well and give a little tweak if neccessary.

Wideband are less widley used and are probably more expensive due to lower volumes and becuase they can cover a larger range of AFR's. Lets say from 0.5 to 1.5
Obviulsy we can use these to give us the bigger picture.
well thats how I see it anyways

Edited by PaulM on 7th Apr, 2004.

9 valves, 4 wheel drive, 3 cylinders, 1 turbo, which got nicked

Ok here goes...

Narrow band sensors are fitted to 99% of ECU'd cars and there purpose is to control the catalytic converter. So really you need to understand cats a little too.... Cats do three jobs (hence being called three way cats).

convert oxides of nitrogen (NOx)
convert carbon monoxide
convert hydro carbons (HC)

The trouble is it can either reduce NOx or it can oxidise the HC and CO... to reduce it needs to run slightly rich and to oxidise it needs to run slightly lean, now when I say slightly I mean a TINY amount... we'll come back to this later!

The control for the mixture is the lambda sensor... cats only work around the stoichiometric point where lambda =1. This is when are air fuel ratio is 14.1:1

So its only at steady state (i.e. cruising or idling) that the cat does much! The ECU alters the fuel by about lambda 0.95-1.05 so that it oxidises and converts at roughly the same time.

This is where the difference in lambda sensors shows up? most sensors are 4 wire types, these are cheap and easy to find. BUT and it?s a big but they are only good over a very narrow range of air fuel ratios. They don?t need to see outside the band of 0.9-1.1 as that?s all that is need to operate the cat. Wide band sensors on the other hand have 5 wires are much more expensive but can see a huge range of Air fuel ratios 0.7-1.5.

The narrow band can be thought of as a tip switch and such is not much good for tuning purposes!

Does that help?

Alex

AlexF

yes alex, that helps explain it a lot. many thanks.

So presumably that means that the Aussie kit uses a narrow band sensor, (since it only has 1-3 wires iirc) wheras the more expensive setups have the wide band.

so what does the bloke who was offering them on here actually sell?

Any ideas? Hopefully he'll see this, otherwise ill email him i suppose.....

Pete

And on the 7th day........... God created turbochargers!

I am selling a narrow band kit for this price!
My DIY wideband kit cost me about 300 pounds.
I asked Jim to post a a picture - so you can have a look at it!
Harry

Edited by Jimster on 8th Apr, 2004.

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

Many thanks for replying to the thread, saves me having to look for you! lol!

I sort of guessed that you would be selling a narrow band kit i must admit, but wanted to make sure.

What is the actual difference in the kits. I think i understand the difference in what they do (ie the readings they give) but why couldnt you take a narrow band kit and add a wideband sensor? Im certain that this is not possible, but could someone please explain why not?

Also what do people run in their cars?

Turboharry - wideband

anybody else run wideband, or do the rest of you use narrow band??

Sorry for all the questions, but once i get started i like to carry on till i understand!

Pete

And on the 7th day........... God created turbochargers!

Picture posted for you harry,

I run a narrow band

Team Racing

Ok, ive got a narrow band unit on order, just merely for trial purposes until i fit the turbo. a few things are now puzzling me.

1) how do i set the unit to the stoichiometric wossit point without the use of a gas analyser?

2) on a turbo, you can fit the lambda sensor to the exhaust elbow?on non turbo units with LCB, where is it fitted?

3) what is the nominal voltage output of a lambda sensor at the stoichiometricythingy point? (could be used to set the sensor in the nominal point??)

4) Will any 3 or less wire lambda sensor do? theres loads on ebay!

Many thanks

MM

Sooperdooperturbocooperexpertengineering!

1&3) I seem to remember that the output of a Lamda sensor is 0 to 1 V in 0.1V increments. I assume lambda = 1 at 0.5V.

2) where to fit it on an LCB, Humm? I guess it would be best after the Y piece, but you could just put it on the centre branch, don't know what's best.

3) As for how many wires, the lambda sensor basically uses 2 wires. Any other wires in the sensor are for a heating element. I use a 2 wire one and just wait for it to heat up (it dosen't take long).

wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

cool,

what circuit are you using? i particularly like the ones that are std round gauge size, but cant find any in the UK.

Oh, and there isnt many sensors on ebay anymore... was a week or two when i looked last D'oh!

Sooperdooperturbocooperexpertengineering!

The stochiom. point is not really of interest for us "look after power" guys. On full power I look to have about 900mV output (1. yellow LED) of the lambda probe. On cruise I lean my engines until any LEDs is lit, but the engine must not start to misfire. (Leaner than Lambda 1!)

On the turbo I put it into the downpipe - On the na engines I put it into the Y-piece. (To collect gas from all cylinders!)

I use the 3-wire lambda sensors: One signal, 2xheater. I don't use 1 or 2 wire sensors because they are not heatedand sensor temp. has an effect on the signal output.
(by the way: 4wire: 1xsignal, 2x heater, 1xground)
Harry

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

what units do anyone here run? home made or bought ones?

Sooperdooperturbocooperexpertengineering!

I received a set from TurboHarry today, will fit it this weekend , but wont be able to try it until I got my intercooler tubing's sorted out. Thanks turboharry for fast delivery. Superb service.

http://www.ktv.no/~pjb-ktv/

Harry,
How much is your AFR Kit ?

9 valves, 4 wheel drive, 3 cylinders, 1 turbo, which got nicked

I believe it is 150? + postage

http://www.ktv.no/~pjb-ktv/

Peter,
Do you know if thats wide or narrow band ?

9 valves, 4 wheel drive, 3 cylinders, 1 turbo, which got nicked

Hi Paul!

It is narrowband! See picture above! And yeah, price is 150 Euro (about 100 pounds) + Postage.
Harry

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm