Solution to LM-2 vs HP Tuners match

[Ben Charles]

Hey Bill, thanks for the reply. I had the EIO LM2 equation setup at volts/.625 +13.1, this read correctly at idle, but was 1 point off at WOT range (13.0 range). Stoich is defined as 14.68 in the tune and I believe 14.7 in the WB (I didn't configure it). I believe I am going to use the VCM controls to command around 13.0 and see how the WB reacts/matches.

Also there is no reason to create your own AFR Error PID when using EIO/Pro. Once you have an air fuel ratio sensor defined (WB PID) it uses that for SENS.120 (AFR) and the built in AFR Error PID compares that to SENS.121 (commanded AFR) and give you the AFR error.

I was having a brain fart that day, lol. In my table I was logging AFR error (PID from hp tuners) and I was getting the percent difference in the scanner, but I couldn't figure out how to in the histogram. Should have just put that PID into a histogram, DUH.

[5_Liter_Eater]

volts/.625 +13.1 doesn't seem right at all. You need to hook it up to the LM Programmer program loaded on a laptop to configure or at least verify the min and max AFR and voltage ranges and define stoich. I think default is .5 to 1.5 lambda (7.35 - 22 AFR) over 0-5V and 14.7 for stoich. The equation is Volts/(voltage range / AFR range) + min AFR. So if it's set up as default then the equation would be Volts/5/14.65 + 7.35 or Volts/.341 + 7.35.

[jimmyb496]

Bill, I've read in several posts spanning back to probably 2008 where you've mention the SENS.120 automatically picks up your user define WB sensor. You've stated that you just need to identify it as the AFR sensor.

I know it may seem obvious, but I just wanted to verify what you meant.

If the image, if I select "Air Fuel Ratio" in the Sensor drop down box, then this user defined LC1 that I've created should populate the SENS.120 parameter?

On a bigger picture, this drop down box is "you are telling HPT what SENS. code this user defined sensor's inputs are intended for"?

[5_Liter_Eater]

Thats correct. If you look at the built-in EIO wide band PIDs they are all defined as air fuel ratio meters. So when you define a user defined PID as an AFR meter, it populates as SENS.120 which is what the built in AFR Error PID uses to compare against PID.121 (commanded AFR) to calculate the AFR error. This is also what screws people up who create user defined PIDs for boost and define them as a manifold pressure sensor; it takes over the MAP PID/sensor and makes things read weird.

[jimmyb496]

Thats correct. If you look at the built-in EIO wide band PIDs they are all defined as air fuel ratio meters. So when you define a user defined PID as an AFR meter, it populates as SENS.120 which is what the built in AFR Error PID uses to compare against PID.121 (commanded AFR) to calculate the AFR error. This is also what screws people up who create user defined PIDs for boost and define them as a manifold pressure sensor; it takes over the MAP PID/sensor and makes things read weird.

That's great to know... could have many useful applications.

[jimmyblue]

All of this fails to account for the variability in ground offset,
which you cannot know in-the-moment. That all is from the
heater electrical load, which will depend on outside temps
and in-pipe gas temps.

The only right answer is an instrumentation amplifier to take
out the ground offset error at the source. I've built various
versions and these do the job. This one includes a charge
pump to make isolated split supplies from IGN power, no
batteries required. Needs a little work on the mechanical
robustness.