AEM 03-0300 wideband O2 logging with 7427

[updatelee]

So usually I ask questions but I figured this one out before I needed to ask, so hopefully this information helps others.

I bought a AEM wideband, I wanted the display on the dash but I also wanted logging capabilities. I'm obsessed with logs lol. The problem was clearly the WBO2 formula was not correct for this device.

X * 0.039063 + 10.000000

AEM manual lists (2.3750 * Volts) + 7.3125 so being someone that loves math, out came the pen and paper. I need to convert X to V. Lets start with what we know, its an 8bit variable and 0-5v input. Ok so for max resolution the variable probably doesnt got 0-5, they probably use more then the first 3bits. A quick log and sure enough I was bouncing around a value of 160, +/-5.

160 = 1.6v ? nope the chart says that would be around 11AFR

what if they used the whole 8bits for max resolution? thats also common. 5v/8bit = 5/255 = 0.0196. we divide 5v into 255 slices, each one equals 0.0196v. So 160 * 0.0196 = 3.136v which on the chart is more then 14.4 and less then 15AFR. Yup thats it.

so the formula is ((X*0.0196)*2.3750)+7.3125

but that can be shortened to (X*0.04655)+7.3125

Sure enough it works perfectly.

Hope this helps someone else :)