How to: Adjust External Calc: Wideband O2 Setting form my .?

[Earl H]

I'm trying to figure out how to adjust the external wideband 02 calc for my wideband (AEM UEGO). I know you are supposed to go into the SAE_GENERIC.TXT file to adjust some of the calc. As close as I can tell this is the area that would be "tweaked":

#Units Low High Fmt Op Factor Offset
#------------ ------------- ------------- ---- - ------------- -------------
*UNM-16-901
V 0.0 5.0 .2 / 204.6 0.0
AFR 10.0 20.0 .2 / 102.3 10.0

Is this correct? Can anyone explain: Fmt Op, Factor and Offset and what impact changing these values would have? Thanks in advance for the help.

[jfpilla]

I'm trying to figure out how to adjust the external wideband 02 calc for my wideband (AEM UEGO). I know you are supposed to go into the SAE_GENERIC.TXT file to adjust some of the calc. As close as I can tell this is the area that would be "tweaked":

#Units Low High Fmt Op Factor Offset
#------------ ------------- ------------- ---- - ------------- -------------
*UNM-16-901
V 0.0 5.0 .2 / 204.6 0.0
AFR 10.0 20.0 .2 / 102.3 10.0

Is this correct? Can anyone explain: Fmt Op, Factor and Offset and what impact changing these values would have? Thanks in advance for the help.

Hang in there Earl. I think a lot of us need the answer.

[Steve Bryant]

Guys, I'll look into it in the next couple of days. I have out of town company, but this is on my to do list.

All my best,

Steve

[GMPX]

Sorry Earl, I am not sure, when Paul gets a breather from shipping orders I'm sure he'll respond.

Cheers,
Ross

[AllCammedUp]

I'm trying to figure out how to adjust the external wideband 02 calc for my wideband (AEM UEGO). I know you are supposed to go into the SAE_GENERIC.TXT file to adjust some of the calc. As close as I can tell this is the area that would be "tweaked":

#Units Low High Fmt Op Factor Offset
#------------ ------------- ------------- ---- - ------------- -------------
*UNM-16-901
V 0.0 5.0 .2 / 204.6 0.0
AFR 10.0 20.0 .2 / 102.3 10.0

Is this correct? Can anyone explain: Fmt Op, Factor and Offset and what impact changing these values would have? Thanks in advance for the help.

Hang in there Earl. I think a lot of us need the answer.

Earl,

Paul is definitely the best one to respond to this. What we do know is that you have to set the low/high in the V entry to correspond to the voltage your unit reports back to the interface. The fmt should stay the same. It's the scale, offset and operand that would control how EFILive reports the data (however, I think the operand would probably stay the same for all wide-bands, but that's going to depend on how it reports its data and correlates that to a number - see below).

Here's what we do know: The PLX reports stoichiometic (14.7:1) @ 2.35V. From data on the PLX website, the PLX reports it's AFR with the following formula: AFR=((2*Volts)+10). In the included SAE_GENERIC.txt, the V factor is equal to the AFR factor * 2, and the AFR offset is equal to 10. Based on that, you could probably come close to plugging in the values for the EUGO. Now - how does one go about determining the originating AFR and/or V factor- that's the real question, because I'm not sure where that number actually comes from.

Hopefully Paul can weigh in on this and give us the final part of the answer. Thanks.

[Steve Bryant]

The crux of how the external 0 - 5 VDC output is converted to a wide band AFR for display and recording via FlashScan and EFILive V7 Scan is to be found in the file sae_generic.txt which is located in the Configurations Folder/subdirectory of your EFILive (see excerpts from this file below. The External PID's portion says that there is a parameter with the description of EXT.AD1 meaning the external analog to digital input number 1 which lies closest to the ALDL/OBD2 connector on the FlashScan unit. The middle input is ground or earth reference and the terminal nearest to the ALDL is high (or positive in this case). External input number 2 uses the same ground reference terminal and the high input is closest to the USB connector. Paul set up the EXT.AD1 function to parameter number F400 (which is a hex number set aside for this type of thing) and further assigned the definition of how this parameter is processed to Slot UNM-16-901 with the applicable engineering units of V (volts) and AFR (Air:Fuel Ratio).

Now look further to the Unsigned Numeric section and you will see how UNM-16-901 is calculated/displayed and eventually recorded. I don't fully understand why Paul did this portion the way he did. However, it says that the voltage input is set up for a range of 0 to 5 volts with a precision of 2 decimal points. This voltage value is divided (/ slash operator indicates that the voltage becomes the numerator and is divided by the factor which becomes the denominator) The Offset is algebraically added to the result (dividend). Then the dividend is divided 102.4 and added to an offset of 10 to yield an AFR in the range of 10 to 20. This confuses me pretty much right now and yet I know that it works correctly on my vehicle!

The PLX M-300 (which is the default WBO2 system set-up for FlashScan) uses an equation that says Voltage Output X 2 + 10 = AFR. therefore I would have set up the units as shown in the second example.

I'm sure that there's an easy answer to this puzzle.

Steve

[jfpilla]

Steve,
This is not one of my strengths, but I was planning on this.
*UNM-16-901
V 0.0 5.0 .2 / 204.6 0.0
AFR 10.0 20.0 .2 / 102.3 9.0

I use a Tech Edge WB. Output voltage is linear and updated at least 20 times/sec. The conversion formula is: AFR=(Vlin*2)+9.
Am I close?

[Steve Bryant]

Joe,
It looks good to me, but I still don't understand the 204.6 and 102.3 business except the first number is twice the magnitude of the second. However, your formula parallels Paul's in all the right ways and if the offset is 9 instead of 10 as with the PLX, you should be good to go. I'm waiting for Paul to get involved to resolve this for sure.

I looked up the AEM UEGO website earlier today to see what their voltage output formula is, but I couldn't find it on their web site. Do you know where this information is on the web? I can see from what you've put down that it is volts out times two plus nine equals AFR.

Steve

[jfpilla]

Joe,
It looks good to me, but I still don't understand the 204.6 and 102.3 business except the first number is twice the magnitude of the second. However, your formula parallels Paul's in all the right ways and if the offset is 9 instead of 10 as with the PLX, you should be good to go. I'm waiting for Paul to get involved to resolve this for sure.

I looked up the AEM UEGO website earlier today to see what their voltage output formula is, but I couldn't find it on their web site. Do you know where this information is on the web? I can see from what you've put down that it is volts out times two plus nine equals AFR.

Steve

Be nice if the formula is that simple.

[Steve Bryant]

Joe,
For some reason I was thinking about the AEM UEGO AFR meter rather than the TechEdge unit you built. I looked up the data on the web for TechEdge just now http://www.techedge.com.au/vehicle/wbo2/1v5/techo.htm and I do think that you have the formula right. However, soon we'll both have a better idea on this. You'll know right away once you hook the WBO2 output up to your FlashScan interface and log some data. They should agree and you'll be able to tell that right away.

All my best,

Steve