Wideband/Narrowband AFR

[xsnapshot]

The stock is kinda a wideband with a very limited range.Sad part about that is the ECU doesn't use O2 feedback at WOT as it goes into "openloop" and relies on the MAF sensor for the primary fueling data.

I wonder why car companies do not do that? It would make so much sense. Maybe someday, someone will come up with such a program to modify the subaru ECU.

Donkey what's your take on the EWG in regards to the lambda values being read downstream?

[Sinister]

Sad part about that is the ECU doesn't use O2 feedback at WOT as it goes into "openloop" and relies on the MAF sensor for the primary fueling data.

If you move to Hydra, or Autronix, it does though... right?

[Sinister]

The stock is kinda a wideband with a very limited range.

I was under the distinct impression that between 11 and 21 the ECU is actually pretty close to accurate. Is this what you mean that stock is "kinda" a wideband?

[Donkey]

I wonder why car companies do not do that? It would make so much sense. Maybe someday, someone will come up with such a program to modify the subaru ECU.

Donkey what's your take on the EWG in regards to the lambda values being read downstream?

Newer Volkswagon and Porsche come with true wideband sensors and their ECUs use constant O2 feedback.As far as the EWG I would think the sensor would read the same as the only the only thing that is changing is exhaust volume,not exhaust content.

[Sinister]

As far as the EWG I would think the sensor would read the same as the only the only thing that is changing is exhaust volume,not exhaust content.

Exactly. It's a air to fuel "Ratio". The same exact wideband sensor can be used on anything from a honda to a bugatti, which obviously have very different volumes.

[mycologist]

They say that exhaust leaks can introduce air. I don't really understand this in terms of EWG though as people stick them in tailpipes that are open. I don't think an open dump tube is the same as a leak midstream where weird pressure differences occur between pulses that could suck in air.

[Sinister]

They say that exhaust leaks can introduce air. I don't really understand this in terms of EWG though as people stick them in tailpipes that are open. I don't think an open dump tube is the same as a leak midstream where weird pressure differences occur between pulses that could suck in air.

since the EWG only opens under high pressure, there is only exhaust gas going out, and no fresh air coming in. It won't allow any additional air into the exhaust. It won't mess up any O2 readings.

An exhaust leak would have to be pretty large to skew O2 readings. There could possibly be a venturi effect where the exhaust that is flowing by the leak will cause a suctioning effect and pull fresh air in. But again it'd have to be a pretty major leak.

(if someone needs an explanation as to the venturi effect just ask)

[Sinister]

donkey... please reply to my top 2 posts of the page kthnx

[Donkey]

If you move to Hydra, or Autronix, it does though... right?

I belive so as this is required for the "automapping" feature to work on the Hydra.

I was under the distinct impression that between 11 and 21 the ECU is actually pretty close to accurate. Is this what you mean that stock is "kinda" a wideband?

The stock sensor is a wideband,just with a very limited range.The farther the stock sensor gets from stoich,the less accurate it becomes.Part of this might be because of where it's located.Basicly I would pretty much always use my LC-1 data over the stock sensor and would suggest others not rely on the stock sensor data for tuning.

[mycologist]

When I get some time I'll log it against my LC-1 and make a graph. I can just use the LC-1 for the x axis and plot out the factory unit (should show the curve even if it isn't in voltage).

[xsnapshot]

When I get some time I'll log it against my LC-1 and make a graph. I can just use the LC-1 for the x axis and plot out the factory unit (should show the curve even if it isn't in voltage).

Good idea. I'll volunteer to do the same with my AEM wideband. Maybe we can get a couple people to do this and see just how accurate the stock sensor really is.

[Sinister]

That would be amazing

[Donkey]

When I get some time I'll log it against my LC-1 and make a graph. I can just use the LC-1 for the x axis and plot out the factory unit (should show the curve even if it isn't in voltage).

I had done this but can't find my data.I have 3 computers and a couple thumbdrives it could be on.Romraider and NASIOC have some graphs/threads as well on the subject.

[mycologist]

Myth busted. We cannot say the factory unit is accurate in the 11.0 bottom end range where we actually care about AFR for our maps.

I just did WOT data where it is really important and where the factory unit is static so that time lag between logging parameters is not a factor. If anyone can send me more WOT data this just represents the range my map hits (so if you have a richer map etc. we could fill it out). Maybe logs with nothing else but AFR so the readings are contemporaneous would show a larger range accurately.

The center dot is the factory reading (always 11.02), the rest are 37 independent LC-1 readings.

[xsnapshot]

nice work! I've been trying to compile some data and noticed a similar random number set. Except i believe on the Acessport it reads a static 11.13. Ive had wideband AFR's from 11.0-12.2 and still had the static stock oxygen sensor reading of 11.13.

I'll send you my data when i get a good compilation of it. Im a little limited as im not able to log the WB AFR's with the accessport data, so my only definite data comes after peak torque when the AFR's settle in and remain fairly constant. Then i can compare the AFR's with the logs with respect to time.

I have a feeling the factory "Open loop" point, occurs near where the stock "wideband" oxygen sensor reaches a point where the back pressure from the turbo starts to skew the incoming data signficantly....(that and the EGT starting to go up)