mark944turbo

I have my air fuel ratio signal from my tech edge computer hooked up to the link box and it is datalogging fine, but my values at idle are always 255. What formula can I use in excel to convert this to an actual air fuel ratio? Anyone know why it is topping out at 255? Is that 5v?

Duke

I think 255 is the highest value meaning it should be 5 volt. But is too high so it makes me think something else is up..

Do you have the Tech Edge display? If so, what does it read at idle?

hally

Hey Mark which of the cables (length) do you reccommend with the tech edge.

special tool

Do you have it connected to a 0-5 volt sensor in on the link? Also, if you don't get any reading change, did you let it run more than a minute - they will read 20-1 for 45 seconds or so.

Sami951

Yeah, 255 is the highest value it'll show, the input is scaled so you can get the actual voltage by dividing the input by 255 and then multiplying by 5

Vin = (input value/255) * 5V ..

In any case it probably shouldn't read 255, as that would be 20:1 a/f and it just wouldn't idle ... check the wiring, I think something's not right.

Oh yeah, the formula to get A/F out of the wideband signal is as simple as (10 + 2*voltage):1
so 2,5V would be 15:1, 0V would be 10:1, 5V is 20:1 and so on..

mark944turbo

The tech edge display reads 14.5 to one at ide.

Hally which cable are you talking about, if you mean the o2 sensor to computer wire i got the 10' one.

Right now I have the signal from the tech edge going into the o2 column in my datalogging, when it probably should be going under 'afm'. I need to change this wire. Does anyone know which pin the afm input is on the link box? I cant figure it out.

Thanks Sami for the formulas!!!!

Sami951

Mark - yeah, you need to change the wire. O2 (lambda) input is for a 0-1V signal, so no wonder you're pegging it

If you have the Link AFM manual, the connector layout should be shown somewhere in there. If not, I can try and find mine, but it's going to take a few days...