mutant_matt

Also posted on 22b.com....

Chaps,
I've been looking at the output of the Lambda sensor on a few MY00/99's (UK), including my own and comparing those to some outputs on some STI7's.

It seems that most UK cars run in the 0.91-93v range (based on 0.88 = 8%CO and 0.90 = >10%CO) and STi's in the 0.95-99v range. Does anyone know if the Lambda sensor is the same (front 99/00 vs rear 01/02) and if the voltage returned "means" the same?

I'm curious because either the new cars run even more stupid rich than the old cars or there is a subtle difference? Having asked that, does anyone know if you can actually determine fueling from the Rear LS on the new cars (or does it have to be done by the Front LS) and does a cat upstream of the sensor have a bearing on this also?????

Anyone know where I can get Lambda output voltages and their meanings for the new shape? (I've got the Link manual for the old shape).

Lots of Q's. Anyone any ideas? Pat?

Cheers,

Matt

Pete Croney

The rear O2 sensor readings will be similar, but not be the same.

The gas they read has been treated by two cats and things like EGT and volume of gas passing through the cats will have a bearing on the amount of oxygen present. If the gas is cold, so the cats are not running very efficiently, there would be more oxygen present than if if they were hot. Equally, cat efficiency will tail off with the volume of gas going through, so you would need a correction for throttle position and rpm.

It would be easier and more accurate to read it from the wideband lambda in the manifold, but a standard LambdaLink won't do this as the voltages are much higher.

mutant_matt

Thanks for that Pete. Thing is, the STi 7's I'm talking about have no cats in them so the figures in question still puzzle me. Also, I thought on a Wide Band LS, you need to take into account temperature compensation so the voltages coming out of one of those will bear no relation to a Narrow Band one? Even if you put a volt meter on a WB sensor, wouldn't the reading be meaninglesss with out taking into account temp compensation and how does *that* work? (is it another output off the LS which has to be taken into account or do you need an EGT monitor and have to take *that* into account???? )

Anyone else?

Cheers,

Matt

BugEyed

Matt

Take what i say with a large pinch of salt, but ...

• The front O2 sensor on the WRX is a wide band one, as you say. IIRC this operates on a 5 volt range and therefore is completely different to the rear one on the WRX and front one on the STi (which is narrow band, and hence operates on a 1 volt range). Comparing voltages will be completely incorrect unless you have a way of deciphering them first.
• As Pete C says, you would get different readings from two identical sensors due to their positioning. Ignoring Petes' correct comments on cats as you say they aren't fitted on your cars, you would still get different readings due to different radial positions in the pipes, different gas temps, and different gas velocities.

Hope that helps.

Duncan

[Edited by BugEyed - 4/17/2002 2:22:56 PM]

mutant_matt

Duncan,

I'm not sure I got all you points (a little confusing to read) but as I understand it:

1. The pre MY01 has a Narrow Band in the DP
2. The WRX and the STi have a Wide Band in the DP
3. The WRX and the STi have a Narrow Band in the mid section

So does it follow that the same NB sensor in the mid will read richer than the same sensor in the DP? Can position really make that much difference and what about the temp compensation stuff????

Matt

P.S. I think the WRX (but not the STi) has some sort of EGT sensor/switch in the up-pipe? What's this used for? Anyone?