Logging wideband O2 with stock PCM and Datamaster – WRITEUP
 

Hi there,

Since I have not seen or heard of any actual information on how to log WBO2 signal thru the stock PCM with Datamaster, I decided to share my knowledge and do a “tutorial” kind of writeup on this subject, the way I have made it to work.

Please note, that I don’t take any responsibility for this information, and this is applying to the Innovate LC-1 wideband setup, which has a linear, programmable 0-5V analog output. If you have a different WBO2 controller, you should check for these features, and you should recalculate the equation below with the relevant AFR vs Voltage figures.

The purpose of this project is to log RPM and other relevant engine data with WBO2 signal at the same time, in the same program, so it would enable to plot a synchronized AFR vs. RPM table for WOT fueling calibration.
There are different ways to log these parameters with so called “aux boxes”, but since I was too cheap to buy the extra (and way overpriced IMHO) rpm signal stuff, and didn’t want to deal with too much extra cables and connections, I decided to give it try thru the stock PCM.

So, here’s a list of equipment you will need:
- OBDI ALDL cable (from akmcables.com or moates.net)
- Datamaster EE from TTS (a trial version can be downloaded at ttspowersystems.com)
- WBO2 controller with programmable, linear 0-5V analog output. (your choice)
- computer (obviously)

We need to feed the 0-5V output of the WBO2 controller to a 0-5V analog input in the PCM. The best choice is the A/C pressure sensor, since it is not used for normal engine operation, and most of you have probably already deleted A/C.
After you have wired in the wideband controller and it is fully working, hook up the wideband controller analog output signal wire and the analog output ground wire to the relevant A/C pressure sensor connectors. The unused sensor connector can be used for a really clean install.

Now comes the tricky part. If you check it in Datamaster, the A/C pressure field will show PSI values which we’ll need to convert to AFR. According to the datastream information for ’94-’95 LT1 F-cars, byte #30 is for A/D RESULT FROM A/C PRESSURE TRANSDUCER. This byte reports raw data called “N” which we’ll need to convert first to Volts, then to AFR.

Conversion function according to the datastream information is VOLTS = 5N/255, from which we get the integer VOLTS= 0.019608*N.

Now, that we’ve got the conversion of raw data to volts, we need to figure out the relevant AFR values. The default analog output of the LC-1 is 0V=7.35 AFR and 5V=22.39 AFR.

http://www.hungryta.com/pictures/WBO2/capture_3.jpg

Since this is a linear output, we can easily calculate the relevant graph equation, which is AFR=3.008V+7.35.

Note: if you have a different wideband controller with different Volts vs AFR relation, you need to calculate the correct linear equation!

Replacing V with the integer above, we get AFR=(3.008*0.0196)*N + 7.35 which equals AFR=0.05896*N + 7.35 ; this function will convert raw data N to AFR.

Now we need to program and display this information into Datamaster, for which we’ll use the Custom Data feature. Click View > Custom Data. On the “Custom Engine Data Display” panel, double click on the first row <Click to Assign>. Fill in the following definitions in the Data Definition table:

http://www.hungryta.com/pictures/WBO2/capture_4.jpg

- Check “Variable Enabled” box, this will enable to display our custom engine data
- Byte Number: 30, this is the byte # in the PCM datastream responsible for A/C pressure raw data “N”
- Information: Air / Fuel Ratio, or anything up to you
- Variable Name: Wideband O2
- Units: AFR
- Gain: 0.05896 ; this is the value from our function above to multiply with raw data “N”
- Offset: 7.35 ; this is the offset value from our function above that is added to the Gain integer
- Data Type: INT ; select this as this value is an integer
- Display Format: 0.00, this will show values of up to 2 decimals

Click OK, you are done!

http://www.hungryta.com/pictures/WBO2/capture_1.jpg

http://www.hungryta.com/pictures/WBO2/capture_2.jpg

You are now able to see WBO2 AFR and RPM at the same time, with all other engine information. Use your favorite dyno tuning spreadsheets to determine new values for the PE tables.

I hope this writeup will benefit for some people and make WBO2 tuning a lot more easier.

If you have some question, please feel free to ask.

Later,
Victor

Nice writeup. I did the same thing. You can't seem to export custom data so I did something very similar in a spreadsheet. In order to get more accuracy and resolution I have a calibration section too. The results from the AFR section are automatically inputed to the tuning section.

If only I had the time to ever work on my web site again I'd put it on the web :(

Nice thread, I've been to Budapest and it was Life changing

Awesome!

Dan

sweet write up man! Keep up the good work..hows the car runing with a new tune? Any more problems with the BLMS?

Guys, I'm glad you liked the info!

Buttercup, why would you want to export the data to a spreadsheet?

JWS6, gimme some info! Have you had the pleasure to try out one (or two) of our world famous ladies lol :D

Marcin, the new tune is fine, although I need some more tweaking with the low pw offset adders, as part throttle is still a biatch.

datalogging
 

My question is, will this work on the '93? It sounds like a great way to get the info I need to correct the tuning on my LT1. Thanks for this excellent post!!!

Yes, I see no reason why it wouldn't work on '93s. You'll need the Datamaster DA version (right click save: http://www.ttspowersystems.com/softw...A/setup-DA.exe)

I don't have bitstream info for '93, but if it's not byte 30 for A/C pressure, then it wouldn't be so difficult to find it either.

Great writeup. I went to Budapest a couple of years ago.. that place is amazing:D

This is AWESOME! This should be a sticky.

Sorry to bring back this old post, but I am just getting around to the install.

I've got everything installed and I'm trying to configure Datamaster. I currently have the brown wire from the LC1 connected to the red/black wire from the pressure sensor.

When I open datamaster and go to view, I don't have a "custom data" field. Can this feature only be viewed and changed while connected to a running car? Does it need to be changed every time I intend to scan the car and record the wideband? Will it save the info for the next scan?

The custom data feature is only available in the new version of Datamaster! www.ttspowersystems.com

Damn, I guess I better download the update. Thanks for the great post and the help.

wow thank you!!! I just ordered an LC-1 and ive been looking for this kind of info. definitely should be a sticky!!

This is impressive ingenuity but doesn't a/c activation affect the mapped fuel and spark tables in the pcm. More accurately, won't a false input to this circuit cause a change in the commanded performance? Forgive my ignorance; I am only beginning to look into tuning. I just have the efilive flashscan v1 and innovate LM-1 but have been eyeing the tuning demo.