Inaccurate wideband readings

I recently set my std. hptuners scanner to work with my wideband using my ac pressure sensor input to the pcm. However there is a slight issue...

I just realized something very important AFTER tuning my ve and maf tables. My scanner and lc-1 dynotune wideband display do not always match each other!! For instance, at 14.7:1 my display and scanner match. However the richer my wideband display reads the further away the scanner gets. At 12.0:1 on my display, the scanner is reading 12.8:1. At 12.5:1 on my display the scanner reads about 13.2:1. I found this out when making some wot pulls after tuning my ve/maf tables according to my scanner afr%error. What I noticed is that the scanner was saying is that my afr error is pretty close when in actuality it is a bit rich on my display but not the scanner. So what I did to confirm this was I happened to shut the car down when the wideband display was showing 12:1. So I turned the key on but did not crank it up so I know the afr would not be moving. I compared the scanner and display like this several times.

How do I fix this problem? Is it something in the scanner or something my analog out2 on the lc1 config??

Verify and tell us what AFR and voltage range the LC-1 is set up for as well as your user defined PID for AFR throught the AC. My only guess is that your equation is incorrect.

The lc-1 is setup in the default range. Here is my config file to look at the equation in the scanner. Right now I think the problem might be on the lc-1 configuration. Not sure though.

I would verify the LC-1 settings as I've heard of them losing their config. What is the default settings? 10-20 AFR over 0-5V?

User defined PIDs are kept in the vcm scanner.cfg file. Just copy and paste the text of the string.

the function string for my lc-1 wb is ([PID.7101]/.5)+9.7. this is what everyone else is using right?
I also compared the 2 today again. Turns out when my display is showing lean..ie 17:1 the scanner is seeing around 16.1:1 so it is off on both ends of the scale except for right around 14.7.

You need to understand the equation, not just use what everyone else is using.

What you have now is matching the display at ~14.7, reading fatter than the display on the lean side and reading leaner than the display on the fat side. Its obvious that the equation is incorrect.

Go into logworks and report back with the min and max voltage and AFR ranges.

Ok I double check my logworks analog output1 which is the display and both the logworks program and my display read the same. So I can easily rule out the display being wrong. As for analog out2:
0 volts = 7.35 afr
5 volts = 22.39 afr

Do I just need to change this to...??:
0 volts = 10.00 afr
5 volts = 20.00 afr

Or should I play with my function string in the scanner? If so what do Ineed to do? Thanks in advance for schooling me on this.

update:
Using the direction below I came up with this. Is this correct?
my voltage range = 5 (0-5v)
my device range = 15.04 (22.39-7.35)
my min value = 7.35

so I guess my function string should look like:
([PID.7101]/.3324468)+7.35 = AFR


HP Tuner Scanner

• Now that the wiring is done, you need to set it up in HP Tuners. You will need some information on your specific wideband that will be in the widebands paperwork. You will have to set up a formula to change the voltage (0-5v) into your AFR wideband reading. It will look like this:


VOLTS / (VOLTAGE RANGE/DEVICE RANGE) + (MINIMUM VALUE OF DEVICE READING) = AFR

VOLTS = the voltage that the wideband 02 sensor is putting out to the EGR wire

VOLTAGE RANGE = typically 5v (0-5v), some people use the narrowband 02 input (not recommended) which is 1v (0-1v)

DEVICE RANGE = the range your wideband is set to read. If the wideband is set to read from 10 – 20 AFR, then the range will be 10. If set to read from 8 – 22 AFR, the range will be 14, etc.

MINIMUM VALUE OF DEVICE READING = the lowest number that your wideband is set to read. In the above examples, it would be 10 for the first example, and 8 for the second.


I am using a PLX SM-AFR 250, so I will use it for my example. The formula will be:

VOLTS / (5/10) + 10 = AFR or,

(VOLTS / .5) + 10 = AFR


• The formula for the A/C Pressure switch is the same, you will just have to change the PID to PID.7101.

([PID.7101]/.5)+10 = AFR

Yep. You've got it. :usa: So the equation you have will work (although I'd lose some decimal points) but I would suggest changing the LC-1 range to obtain more resolution. Do you really want to measure 7.5:1 AFR? 10-20 AFR is the largest I would go and that would put you back at PID.7101/.5+10 but also consider tightening it even more. If you're NA then you only really need to measure like 12:1 - 16:1. Once you decide the rance and derive the equation and know that part is right then you need to compare the logworks (or gauge) output against the HPT. If it's off its because of voltage offset. Play with the +10 (or whatever you end up with) to account for that. So if logworks shows 14.7 and HPT shows 14.3 then add .4 to the minumum AFR.

:cheers:

Well how do I change the range? Do you mean changing my analog out 2 in the lc1 config tool to:
0 volts = 10 afr
5 volts = =20 afr

10-20 will be fine for me. I run a 150 shot also, but have no need to scan that since I adjust my fuel jet to get that right.

Yes, using the LC1 config tool, change whatever analog output you have piped into the AC pressure wire to output what you have above (10-20 AFR over 0-5 volts) then use the PID.7101/.5+10 equation. Then adjust voltage offset. If you have another output going to the gauge (Im not sure how the LC1 gauge is wired) then set that output to the same range.

Yea my dynotune display is wired to my analog out1. I know for sure it is set to read 10-20 afr. So I guess my original equation was right in the scanner just have to change things on the wideband config side of analog out2. Thanks.