Weird O2 readings

[sw20kosh]

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

[Kodename47]

When you say this:

Originally Posted by sw20kosh

I have already:
1. tried a buddy's stock O2 sensor. Same result.
2. Recalibrated the wideband in free air. Same result.

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.

[Ross]

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.

[sw20kosh]

Originally Posted by Kodename47

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 re-worded it. Thanks.

[sw20kosh]

Originally Posted by Ross

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.

Back pressure! @jamesm

Voltage offsets? Easy to check this?

[Ross]

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.

[jamesm]

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.

[post_break]

Are you using an analog ground?

[Kodename47]

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.

[sw20kosh]

Originally Posted by post_break

Are you using an analog ground?

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

[post_break]

Originally Posted by sw20kosh

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.

[Sportsguy83]

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

[stugray]

Originally Posted by sw20kosh

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

"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.....

[welllam]

Originally Posted by stugray

"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...