MSefi.com read only forum (Jan.15,2018)

HI, I have a AEM UEGO 30-4100 and I discovered that the AFR gauge in Megatune isn't showing the same AFR as the AEM gauge. The value are close, but no the same. So, I made a simple Excel spreadsheet that show the difference between the true AEM UEGO 30-4100 values and the MT values when the selected wideband is 'AEM Wideband Linear'.

I have found the true AEM values on the aempower website. Here's the link :

http://www.aempower.com/images/products ... 0-4100.pdf

I have found the 'AEM Wideband Linear' formula in the lambdaSensors.ini file under C:/Program Files/Megasquirt/Megatune2.25/mtCfg. Here's the formula :

AFR = (9.72 + (egoADC * 0,038666))

To transform a 0-5 volts source to a 0-255 ADC number, I used this formula :

ADC = Round ((256/(5V-0V)) * ((VoltIN) - 0V))

I plotted both AFR vs ADC curves and you can clearly see the difference.

I made another row called Hypothesis where I played with the original formula to get a curve that overlap the AEM UEGO 30-4100 curve.

Here's the result :



The formula I used for the Hypothesis is :

AFR = (10 + (egoADC * 0,03912))

Now, my question is how do I implement this in Megatune and Megalogviewer? Do I simply replace the old AEM Wibedand Linear formula by the new one in the lambaSensors.ini table and burn in the MS-II the new AFR calibration (In Megatune : Tool/Calibrate AFR table)? What about Megalogviewer? Will it follow?

I've found the formula, now help me to use it!

Thanks

Sam

Ok, I burned in the new AFR calibration (I edited the lambdasensors.ini file with the new formula above). But the results aren't what I expected. I looked at the afrtable.log file and the 0V value is always 9.72 AFR. By my formula, it should be 10.00 AFR at 0V.

I need help about this. How can I make my formula working?

I joined the afrtable.log and lambdasensor.ini file.

Waiting to get some help!

Sam

The AEM Sensor has come up quite a few times....
The published values are what you have there 0V=10:1 5V=20:1 and I'm not sure where the values used came from. I used to assume maybe it was an earlier revision, but a couple years back when I tried setting MLV to use the 10:1-20:1 I got reports of it not reading the same as the AEM gauge. It seemed as though the voltage was slightly different when connected to the MS, maybe a different bias?? Or was there just confusion for a couple people using MLV because MegaTune was reading different?

Any way there are 2 ways you can update your MS2 calibration to have the 10:1-20:1 values. TunerStudio has all the formulas for the WB calibration in a text file ms2ReferenceTables.ini in the inc dir.

Or easier yet, select the "Innovate 0-5V 10:1-20:1" as it is the same as what you posted above for the AEM.

Ok you are right about the 0-5V = 10:1 - 20:1. I'll try the Innovate setting this weekend and I'll report back.

The values I used are from the AEM instruction sheets that are available on the aem website or when you buy a AEM UEGO 30-4100 unit.

My problem for now is when the AEM gauge read 10.0:1 (while I'm boosting, I'm running really rich), the Megatune and MLV are showing 10.4:1.
When the AEM gauge read 14.7:1, the Megatune and MLV are showing 14.8:1. It's off by 0.1 AFR points in the leanest part and by 0.4 AFR point in the richest part.

The other test I'll do is to check if the voltage at the 0-5V output from the AEM gauge (which connect to MS2) is really 0.00V when the gauge is reading 10.0:1 AFR. It will prove if the 0-5V output is OK.

I'll report back!

Sam

The values I used are from the AEM instruction sheets that are available on the aem website or when you buy a AEM UEGO 30-4100 unit.

My problem for now is when the AEM gauge read 10.0:1 (while I'm boosting, I'm running really rich), the Megatune and MLV are showing 10.4:1.

Yep I have seen them, when i first saw it, it seemed simple, just change the formula to a simple linear AFR=10+(O2*2)
which is exactly the Innovate setting anyway.

But, even with the innovate formula it still didn't match the gauge everywhere. I forget who it was playing with it, but in the end they created a new formula by mapping out the readings. It was still linear, but the slope and shift both needed to be adjusted slightly to match from max lean to max rich.

Unfortunately it didn't seem the same results of their trials worked for others. this is when i started to theorize that that current formula in MT an MLV came from just this type of exercise.

I don't have an AEM here to test myself, so i am going purely off hear say, but it seems like something is not consistent. The important thing is to be pretty close at 14.7:1, on the outer edges WB sensors have less and less accuracy anyway, and you don't really know how accurate the gauge is (Easily checked though), so if the 2 disagree by 0.x in the 10:1 range, so how much does it really matter.

Ok, I tried the Innovate 0-5V = 10-20 AFR and it's far off from the AEM gauge. I do not recommend anyone to use the Innovate 0-5V for a AEM 30-4100 gauge. It simply do not match. It's off by 0.4 AFR point in the 12.5-15.5 AFR range. I didn't try it in full rich or full lean for precaution.

Instead of this, I retried the formula I came with in my first post (the one that is called 'Hypothesis') and I burned it in MS2 again but I reset Megatune this time and now I can see the difference. The AFR is spot on from 11.5 to 16 AFR and is a little off in full rich : When AEM gauge read 10.0 AFR, Megatune read 10.3 AFR.

Now, either there is a problem with the AEM analog output not sending 0.00V when full rich (10.0 AFR) or MS2 isn't reading 0.00V at the DB37 pin23 for an unknow reason. Tomorow, if I have someone to help me, I'll check if the AEM analog output is really sending 0.00V when full rich (10.0 AFR) with a multimeter.

I'll report back.

Thanks for the replies!

Sam

Hi Sam!

I'm in the same situation that you are in... even down to the Excel sheet. My current formula is WB02 = 9.3 + ([O2]/5*255 * 0.039216). You can see it is essentially INNOVATE_0_5_LINEAR with a Y-intercept of 9.3 instead of 10. Yours looks more precise...

I hacked the lambdaSensors.ini file to use this formula, for WB_UNKNOWN. Unfortunately that means I need to enter the target AFR's in volts - easily remedied with Excel but its still a hassle. I suspect there's a way to change that, but I need to do some

For the megalogviewer, I checked Calculated Fields -> Wideband O2-AFR -> Custom Linear. Then I put AFR at low voltage 9.3, AFR at high voltage 19.3, low voltage 0, high voltage 5. This works out to the same formula as above.

Now MegaTune matches the gauge pretty well, you have to enter the Target AFRs in volts, but when you go to MegaLogViewer you can see the Target AFR table in AFR, and the correct calculation for the wideband. While it feels like a hack it does seem to be working for me.

If it works for you, this is great!

On my side, the megatune AFR gauge matches the AEM gauge correctly between 11.5 to 16 AFR, but it's off under very rich condition :

When the AEM gauge says 10.0:1 (the richest point the AEM can show), the megatune is showing 10.3:1.

As per the AEM volt vs AFR chart, if the AEM gauge shows 10.0:1, the wideband voltage is 0.00v. I need to put a multimeter on the analog output from the AEM gauge to see if this is really sending 0.00V when the AEM is showing 10.0:1. If it does, than there is a problem inside the O2 circuit in the MS-II that is adding about 0.15v to the signal so that the Megatune is showing 10.3:1...

If the analog output doesn't send 0.00v when the AEM gauge is showing 10.0:1, then there is a problem with the AEM gauge and I'll contact AEM technical support to have them to verify this.

I need to check that, but my radiator is leaking... I'm waiting for the new one to continue the test.

BTW, you have the AEM 30-4100 gauge, don't you?

Sam

Yes, I have the 30-4100 gauge. I didn't realize there would be this much effort to connect it with Megasquirt. I almost wish I bought an Innovate unit like everyone else!

OK, update on this.

After a bunch of testing some formulas, I've ended to simply try to find a nice linear curve by using 2 points and 'Generic WB Linear'. Here are the steps I used to get it done :

1- Enable the datalogging of the channel "O2 volts" in your megasquirt.ini file. This is the channel that will tell us the real voltage coming from the 02 input pin.

2- Datalog a run that include those 2 things :

- AEM gauge show '10.0' during a few seconds
- AEM gauge show '---' during a few seconds

3- On the datalog, retrieve the O2 volts min and max (should be close to 0.000V and 5.000V respectively but not right on it). By example, my min value was 0.35V and my max value was 4.54V.

4- Do a linear curve with those two points :

A (min O2 volt, 10.0 AFR)
B (max O2 volt, 18.5 AFR***)

5- Do some maths to find the AFR at 0.000V and 5.000V. (Remember : y = m*x + b )

6- Enter those points under 'Tool\Calibrate AFR table\Generic WB Linear and burn in the calibration. Do not forget to run the Configurator first to set your wideband as 'WB_UNKNOWN'.

With these steps, my AEM gauge match the Megatune gauge from 10.0 to 18.0 AFR within 0.1 AFR.

*** : The problem is that we do not know what AFR value the AEM gauge is showing when O2 volts is at maximum because the gauge is showing '---' . I supposed 18.5 AFR and it worked nicely for me. Play with this number if you feel you need it.

Hope to help!

Sam

old topic i know...but new to ms and old to aem.

even aem ems has trouble with there o2wb.

the calibration table is correct, its just off a bit.

the change is gain on the 0-5v output from the 4100.

im no engineer to bare with me...in aem you almost always need to lower the gain by .02 as where 1.00 is 0 gain correction and the default setting. so the final gain setting is .98

aem tech will tell you to put a multimeter on the wire and change the gain setting within aempro until the voltage on your meter matches the displayed o2 raw volts within the software.

i think a variable resistor inline the o2 output will allow you to change this "mechanically". i would steal the "gain" pot off an old car audio amplifier.

i hope this helps, maybe at least a little bit to someone.

i run aem ems and uego and have had nothing but o2 nightmares for 5 years until my brother let me borrow his lc1 aem wbo2 = pure crap imho.

but even with the lc1, i still have the gain set at .98 ..this part of the install remains unchanged.

Kawgomoo wrote:old topic i know...but new to ms and old to aem.

even aem ems has trouble with there o2wb.

the calibration table is correct, its just off a bit.

the change is gain on the 0-5v output from the 4100.

im no engineer to bare with me...in aem you almost always need to lower the gain by .02 as where 1.00 is 0 gain correction and the default setting. so the final gain setting is .98

aem tech will tell you to put a multimeter on the wire and change the gain setting within aempro until the voltage on your meter matches the displayed o2 raw volts within the software.

i think a variable resistor inline the o2 output will allow you to change this "mechanically". i would steal the "gain" pot off an old car audio amplifier.

i hope this helps, maybe at least a little bit to someone.

i run aem ems and uego and have had nothing but o2 nightmares for 5 years until my brother let me borrow his lc1 aem wbo2 = pure crap imho.

but even with the lc1, i still have the gain set at .98 ..this part of the install remains unchanged.

could i talk you into talking me thru how to change this. as in step by step detailed. im not the most ms literate person around. thanks alot.

pit_celica wrote:OK, update on this.

After a bunch of testing some formulas, I've ended to simply try to find a nice linear curve by using 2 points and 'Generic WB Linear'. Here are the steps I used to get it done :

1- Enable the datalogging of the channel "O2 volts" in your megasquirt.ini file. This is the channel that will tell us the real voltage coming from the 02 input pin.

2- Datalog a run that include those 2 things :

- AEM gauge show '10.0' during a few seconds
- AEM gauge show '---' during a few seconds

3- On the datalog, retrieve the O2 volts min and max (should be close to 0.000V and 5.000V respectively but not right on it). By example, my min value was 0.35V and my max value was 4.54V.

4- Do a linear curve with those two points :

A (min O2 volt, 10.0 AFR)
B (max O2 volt, 18.5 AFR***)

5- Do some maths to find the AFR at 0.000V and 5.000V. (Remember : y = m*x + b )

6- Enter those points under 'Tool\Calibrate AFR table\Generic WB Linear and burn in the calibration. Do not forget to run the Configurator first to set your wideband as 'WB_UNKNOWN'.

With these steps, my AEM gauge match the Megatune gauge from 10.0 to 18.0 AFR within 0.1 AFR.

*** : The problem is that we do not know what AFR value the AEM gauge is showing when O2 volts is at maximum because the gauge is showing '---' . I supposed 18.5 AFR and it worked nicely for me. Play with this number if you feel you need it.

Hope to help!

Sam

I also have a discrepancy between my gauge and MT. My question is how do I enable O2 volts datalogging in MT? I can get lambda to display, but haven't seen volts. I am using MS-II. I want to try this method above, but would like to datalog the results instead of using a VMM on the output of the AEM. I am guessing I have a voltage bias somewhere, as my MT never goes below 11.3 even though the gauge is reading 10:1 ish.
thanks
Paul