Can't figure out voltage offset for datalogging AEM Wideband

[04GTMustang]

Hey fellas,

I've been digging all over the google trying to figure out how to determine what my voltage offset is. I just wired the firewire cable for SCT x4. I used these instructions:

Connect AEM White to SCT Orange | Connect AEM Black to Vehicle Ground and SCT BLUE

I fired up live link, used the formula for AEM of (v*2)+10 and saw the log was about 1-2 points higher than what my gauge was reading. I saw that you might need to adjust this due to a voltage offset.. But how do you figure this out?

With the key in the ON position but engine off, the white wire from the wideband going to analog orange is reading 4.46V. I'm not sure if my offset would be .54? I put that in and it's still not reading accurate. ((v.54)*2)+10

How do I figure out "voltage offset"? Any does anyone have tips on how to do this with a constant voltage from the wideband so i dont have to try and get it to match watching the afr bounce around at idle?

Thank you in advance.

 

[01yellercobra]

It's been a bit since I've messed with the formulas, but I'm pretty sure you leave V (slope?) alone and adjust the 10 (intercept?) to get the readings correct. I vaguely remember having to do that in my Aeroforce. I would input 9.5 and see what that does. It should give you an idea of which way you need to go.

 

[04GTMustang]

It's been a bit since I've messed with the formulas, but I'm pretty sure you leave V (slope?) alone and adjust the 10 (intercept?) to get the readings correct. I vaguely remember having to do that in my Aeroforce. I would input 9.5 and see what that does. It should give you an idea of which way you need to go.

Thanks for the reply. So I called AEM and asked them, figured why not. Spoke with Caleb, and he really knew his stuff. First, he pointed out the new 30-0300 X-series are no longer using the (v*2)+10 formula, and now use (2.3750 * Volts) + 7.3125.

This basically solved my problem. However, I'll elaborate on another trick he told me on the phone if anybody else is trying to figure out calibration:

To make sure your wideband is accurate, you can remove the sensor from the exhaust and soak a rag with any combustible fluid, and wrap the sensor in the rag. This basically forces it fully rich. So the gauge will read 8.0 which is the richest it can register to the display, and the analog can only see as low as 8.5. So I turned the key, did this trick, and started logging. My SCT software showed 8.47-8.48 (which is basically the lowest limit) which corresponds with the lowest limit seen on the gauge, which is 8.0. This is a good trick versus trying to watch the gauge bounce around at idle while watching what the software is seeing. Should be good to take it for a rip now, I'll report back later.

UPDATE: The new formula of (2.3750 * Volts) + 7.3125 is working perfectly for the x series 30-0300 wideband in livelink.