Weird O2 readings
 

Do you see anything wrong with the below picture? Custom Map M is my LC2 wideband (yellow line). I have been told this looks weird because the wideband should be reading richer than the stock O2 sensor.

Just wanted to get a general consensus on 1. if it is abnormal and 2. if it is, what is causing this anomaly. I would like to remedy the situation.

I have already:
1. Replaced my stock O2 w/ a buddy's stock Brz O2 sensor. Same result as the picture below so that rules out the stock O2 being bad.
2. Recalibrated the wideband in free air. No change.


Yellow = wideband
Red = stock O2
https://scontent-a-sjc.xx.fbcdn.net/...51127251_n.jpg

When you say this:


What do you mean?


Do you mean that your wideband sensor is off from another by the same amount as the stock O2, or that the other wideband is off the stock O2 by the same amount? It's hard to determine which one you mean.

I have found on force induction cars that the factory sensor is rarely anywhere near accurate as back pressure increases. I stop worrying what the factory sensor says and go by my wideband in open loop. I do verify there is not any voltage offsets going on before I trust the wideband as well.

I re-worded it. Thanks.

Back pressure! @jamesm

Voltage offsets? Easy to check this?

A lot of the fi cars I will tune have a wideband already installed. I will verify the ecu is seeing the same voltage as the wideband is putting out. Then I will make the custom tables. It is not super common to see this issue, but some installs may need to be corrected do to connection quality, signal noise, ect. If I am using my lm2 then it is a non an issue.

I believe the ptuning kit is unique in that the front o2 sensor stays before the turbo whereas with most others it's relocated to the downpipe. I definitely suspect that the backpressure under load is what's causing it to peg rich. You don't see that with other turbo kits where it's relocated. In my experience the stock o2 is always off but it usually reads leaner than the wideband, not richer.

I never make custom scaling for the front o2, just use ecutek's provided scaling and tune off of the wideband.

Are you using an analog ground?

I would always take the WBO2 reading over the OEM one. Just because it usually reads leaner doesn't mean that it always will.


As said, it will depend on where both sensors are located too. The further back the WBO2 the more likely it is to read leaner.


I'm with Jamesm in the sense that I would leave the ECUtek advised O2 config as it is and then use a custom map if required to correct fuelling base on the WB if needed.

I am sorry but what does this mean? I am grounding the LC2 to the chassis.

In the manual it says you must use an analog ground, like a ground the ECU uses otherwise your readings will be off. If you use a power or chassis ground your readings will be wrong.

@welllam I think this thread might interest you...

"Grounding" is a science all to itself.
Cars typically use chassis as a "Ground reference" and a "Current return path".
For sensitive electronics (O2 sensors) they need a proper "ground reference" that tells the circuitry what voltage is "Zero volts" as far as the system is concerned.

When you use car chassis as this ground reference, then it is not always at "zero volts" with respect to the rest of the car because the voltage of any particular point in the chassis is dependent on how much current is flowing through chassis and where the current is flowing.

So if you "reference" the O2 sensor to car chassis close to the sensor, then the ground can move up or down depending on if (for example) the radiator fans are on or off. This is because current flowing through the chassis causes voltage drops in this reference.

For the more sensitive sensors, you should run a dedicated "ground reference" from the sensor to the unit reading the sensor.
If you use chassis for this, then the "zero volts" reference is not always at "true zero".
If anyone cares and is confused by this, I could make a diagram.....

If i use the same ground for the aem gauge and also the same for the output ground, is this the same reference?
@Sportsguy83 i connect my ground of both to the same fuse box bolt that you uses and also poeer from the fuse top of the drl. So connection wise it should be similar. Just dont get it...

Yes, you are using my same configuration.... Definitely weird.

If all else fails, I believe you can change the parameters of the custom map and modify them to follow your actual Gauge readings properly.

I might have missed something. What issue is he having?

He has the Failsafe connected like me (the failsafe has an analog output cable which can be used to log via Ecutek custom map), to the ECU via rear O2 sensor connection and his Logs are showing a different value when compared to the gauge itself readings.

Oh gotcha.

I am going to follow these instructions then for grounding:

When all else fails us the battery negative post. With innovate products I find that to help. Have not had an issue with aem units yet

This is where "grounding" gets a little confusing.

The meter/O2 gauge needs +12V power so it needs a ground (called a 'return' in my business because it intentionally carries the return current to the power source).
This would go to the battery negative.

The part of the system performing the voltage measurements within the O2 sensor needs a ground 'reference'.
This ground does not carry any significant current so it does not experience voltage drop during operation.
That ground 'reference' should go from the Measuring unit (gauge or ECU) all the way to the sensor.
Some older sensors (VDO oil pressure for instance) did not provide a dedicated ground to wire to and depended on the car chassis to provide the path.
Newer sensors typically have dedicated reference 'grounds'.

Theoretically, you could hook the reference wire to car chassis at the sensor end and at the gauge end and in most cases it will work.
Is it accurate? Each installation could be different and give different results.

i have also been told the stock sensor reads lean when hot/upper rpms, but my O2 readings are very low 11's to even sub 11's when WOT past 5k rpms on pump gas (91) with the stock sensor. i ended up rescaling my MAF in closed loop since my trims were off a bit. i don't have a wideband so i don't want to rescale open loop myself, but i just thought my logs looked strange... almost identcial to OP's

http://www.datazap.me/u/gabeg86/post...g=0&data=1-5-7

That is way over my head. lol

The LC2 wideband has 2 wires that need to be hooked up. One is a Switched on 12V and one is a ground. The instructions say to use the battery ground (-) post.

The two wires you are talking about are power for the controller.
I would call them Power (+12V - RED) and Return(Ground-Black) and can both go straight to the battery (with fuse of course).
Or can hook to a fuse panel (+) and chassis (-)

There are other wires that go from the O2 sensor to the gauge.
These are in the "Sensor cable connection"
As long as you use the cable provided with the unit, you are fine.
It is when people try to extend THOSE signals you can get into trouble.
The old school thinking is you can just hook up the "ground" in that cable to the car chassis and it will work.
It wont.
If your cable is intact from the factory, then you are doing it right.