Strange lambda reading ...

[Torque]

Hello there,

I had a look at my logs and I found it kinda odd that I my lambda readings are often at ZERO or just very low.
My mixture is definitely not that lean ..

I assume that the Lambda value is volt?

Any ideas?
I have no fault codes from the ECU either ...


Any thoughts appreciated!

[PL]

Probably somewhat unusual but not the end of the world.

You'll normally see the values from the factory narrowband sensor swing between close-to-zero and close-to-1V. This varies a lot from sensor to sensor and on things like sensor age and whether your engine is properly warmed up. Even swinging between 0.2V and 0.8V is OK. As long as it's swinging convincingly either side of centre then it's working.

PL

[Torque]

Hi Pete,

I will probably have an ageing sensor?
Lambda 1 is at about .45V, so I find it strange that the ECU is not chasing Lambda in this region.

Also what is very odd is the fact that left O2 and right O2 are sometimes out of sync.
This can not be since these are soldered together onto one Lambda sensor ..

Also would you know what AFR Learn TP scale stands for?

[Torque]

Hi!

On my way to work a thought struck me ..
When my turbo desintigrated, the Lamda-Sensor took a slight hit.

There was a small dent in the 'nose' of the sensor.
I thought 'doesn't look like much damage'

That must be why the sensor has this readings!!!!
I need a new one ..

[PL]

Hmmmm - I have no idea what that scale is for!!!

PL

[Torque]

Hi Pete,

Thanks ...

Would you know why left and right lambda readings are not always in sync?
(it's the same sensor)

I also bought a new lambda sensor .. will report back once installed.

[PL]

That just makes no sense at all!

So, you're running a single sensor in the RB25, and you've bridged the right/left O2 sensor inputs to the Z32 ECU, but R/L are reading different? WTF??

PL

[Eric]

the 0volt in your logs looks normal to me, seeing the TPS is at 0.4 Volt at the same time...meaning it's happening during off throttle situation = economy fuelcut

[Torque]

That just makes no sense at all!

So, you're running a single sensor in the RB25, and you've bridged the right/left O2 sensor inputs to the Z32 ECU, but R/L are reading different? WTF??

PL

Yes, the connection is there (to bridge the sensor inputs)
Maybe it's just some delay or lag in the ECU or Nistune?

Maybe somebody else can double-check?

[PL]

I'll have to add O2 sensor input to my Z32 test rig. I normally see pretty close to 0V on both sensors that have been modded for R33 as I have nothing hooked up to them at present.

PL

[Torque]

Hi Eric,

So the ECU actually cuts fuel when rolling and the throttle is lifted?
Still the O2-Sensor should output a voltage higher than 0, but I suppose the ECU blanks this out then?

I also checked in older logs of mine, and this behaviour is present from the start of using Nistune (so feature, not bug)

Thanks ..

the 0volt in your logs looks normal to me, seeing the TPS is at 0.4 Volt at the same time...meaning it's happening during off throttle situation = economy fuelcut

[Torque]

Hi,
have checked on other logs and it seems there is some 'lag' between left and right readings for O2

[PL]

That's only a difference of 1mv! What happens once you get some real voltage on there?

PL

[Torque]

That's the trouble .. values just creep around low voltages ..

I will have to install a new sensor and re-test.
(Sensor is here already)

[Eric]

> So the ECU actually cuts fuel when rolling and the throttle is lifted?

Yes in most cases, when RPM is above the treshold values in the tables at #7F40 and #7F50 (not sure if Nistune has these included), a fuelcut occurs as soon as the throttle is lifted.

> Still the O2-Sensor should output a voltage higher than 0, but I suppose the ECU blanks this out then?

No, the ECU won't blank anything out....ideally the voltage should be 0 volt as the exhaust gasses are pure air (oxygen) .
Although the clearing up of the exhaust gasses might take a few (milli)seconds, depending on RPM.
A slight variation in lambda readings may indicate there still is some residue of something else (fuel/oil) in the exhaust gasses, but in most cases it's just a flaw in the sensor itself...

A variation of 0.01-0.05 volt can be ignored (imo).
Narrowband lambda sensors are not the most accurate sensors around and because of this it should only be used for crude diagnosis and never for tuning, as this is where wideband lambda sensors come into play.