ZEN Performance

Huh? Lambda on the 4 gas was nigh on 1 for the test, how can it now be 0.901 at the same time?

dabow

iTrader: (19)

ok, i testard the lamba today

its stays around 0.26/0.28 v

when i first started the car & let it warm slightly. it was at 0.36 v
does this mean i've a dud lamba?

Jolly Green Monster

iTrader: (4)

yes once hot it should be altering not constant

Scott.T@PolarPerformance

BINGO......

The rookie

iTrader: (1)

I've already clearly said it could not possibly be 1....not with that much CO!

Reasonably OK graph at http://www.bridgeanalyzers.com/Docum...Paper%2017.pdf

Simon

dabow

iTrader: (19)

i my self diden't think it would be the lambda as its not very old

ZEN Performance

The lambda as reported by the 4 gas was 1.

The rookie

iTrader: (1)

So you say, the point is at that CO it cannot be at Lambda one, its just not possible - so either the machine is faulty/miscal'd (been there and got that T-shirt) or the OP was misinformed/mistaken, either way 3% CO is not and will never be at Lamda 1! - Yer canna change the laws of phyics Jim!

How many cars have you run and seen 3% CO at Lambda1?

Simon

ZEN Performance

Well here we have the problem you see, which is what you stumbled upon without realising when you we're busy shooting me down in flames.

There are a number of ways to analyse the exhaust gas to determing the input AFR. If you look at the O2 in isolation, then it may give a different result to just looking at the CO or the NOx or the HC. This is where Spindt's model comes into play as it uses CO, CO2, O2 and HC as a means to determing lambda (AFR). If you only use one output as a means of detemining CO then you must get complete combustion for it to be correct and valid. Complete combustion is rare, especially on performance vehicles and especially at lower loads. Where the Spindt method falls down is it doesn't take into account the input water levels (humidity) which will affect the outcome of the calculation. So then you can get the Brettschneider refinement of the Spindt method which accounts for NOx and H20 in the output. There are further refinements, which include a validity check to ensure the answer is valid within a window of extremes for any one consituent.

The upshot of all of this is that the 4gas will create a lambda measurement based on all that it sees (if it's good) not just the O2, or the CO. However an O2 sensor may in effect lie (rich engine with slight misfire will read leaner than reality). The lambda measurement is also a mean, which means you can be going rich/lean and still hit lambda 1 on a 4 gas, the problem is you get be more rich than lean for less of the time and STILL hit a post cat lambda of 1.

I test a fair few cars on the 4 gas prior to MOT time, and you can see all sorts of weird stuff, I can quite believe it's not supposed to be possible, that doesn't stop it from happening all the same. Hopefully for the OP his new lambda sensor and some heat in the cat will sort his problems.

Alan Jeffery

Cut and Paste wars rule again..
Being a practical guy my observations tell me that on the few occasions I've been looking at lambda one AND over 2% CO the lambda sensor has been the guilty party.

dabow

iTrader: (19)

well i'm hoping so mate.

anyways. come on guys, lets not fall out over a thread.
i do know a bit about cars.

morew macanical than anything, you all seem to know of what your talking about. but falling out over

i'll post up the result.

weither it fails again or not.
if it fails again, i'll post up the readings again.

touch wood i have a smile at the end

but a big thanks to alan jeffery, for taking me through the process
it helped a great deal.

& a thanks to all that replyed to the thread
put this thread on hold or untill i get this new lambda fitted & have the retest

dabow

iTrader: (19)

well thanks to scobymad who sold me a nearly new lamba
the car went through its retest perfect

so in the end, it was just the lamba.
so again, a big thanks to alan jeffery
and all the other tuners/mappers who gave advice

well, i guess the car will need mapping soon know
thanks again guys

The rookie

iTrader: (1)

Paul,
Looks like it wasn't running at Lambda one then!

While I understand your concerns, it still won't make lambda1 3%,Spindt has its limitations, but its more accurate than that, and doesn't change the fact that your original claim that a cat changes lambda was eroneous!

Simon

Simon

Jolly Green Monster

iTrader: (4)

glad the lambda change fixed it, could see it being anything else

ZEN Performance

Yes it wasn't running Lambda 1, that is my point. Lambda 1 was the figure shown by the 4 gas, using the spindt calculation that you said couldn't be wrong, remember?

A cat will not change the ratio of air and fuel going into the engine, but it will alter the measured value, which is what I was refering to, not bargaining on the nit pickers.

dabow

iTrader: (19)

me my self, i was suprised it was just that.
how can a lamba change the readings that much

i've had a lamba go before on a vauxhall corsa gsi 2.0 i built.
when the lamba went on that, the reading was 0.52 that was a 95 to

i changed also the throttle control senser, & changed the plug spacing too
with these & the lamba

the car seems to be bloody quick, i don't really want to push the car. as i know i need a remap

well, it suprised me.
as least its done know & taxed

Alan Jeffery

Hey, Dabow, glad it's sorted mate.
I'm always telling the staff, if a car fails the MOT, check what the lambda sensor's doing first.

Scott.T

iTrader: (2)

Glad you got the answer we all expected

dabow

iTrader: (19)

the frantic revs i was getting has also gone.
i guess there was no leaks after all

there was other issues i was having to, but most of the senser around the engine was changed to

well, i'm know saving for this live map & uprated boost map senser
that lamba must have been damaged for a while. when io boot the car know, it dont half shift.

but it should be quicker when mapped....