USB affecting AFR...

[SupSay Z]

hey guys, whats up? first of all, i apologize if this has been addressed here previously, i briefly searched and did not see anything similar. My problem is that my AFR across all rpms was randomly shooting up to 16-17. other times i would start the car and it would be in the 12-13 range, in which for some reason is where she likes to idle. anyways, when i plug in to see whats going on with nistune, afr would go back to normal. on one of the tries i unplugged the nistune usb before the innovative one, and noticed the afr increase as i did that. i plugged the usb from the ecu, without even opening up nistune and afr would again stabilize. i tried this with a usb car charger i have, plugged into the cigarette lighter and it would work stabilizing the afr as if it was plugged into the computer, but, i dont want to keep doing this simply because its not how its supposed to be and i dont want to risk shorting out the ecu. any ideas guys? thanx for reading this..

alex

[bachig24u]

It is noted that a common earth is required.
Earth ECU, Laptop, Lambda in same location.
See if it helps.
Any variance in Earth/Ground points will affect the reference for that device..

let us know how you go.

[SupSay Z]

i understand what u mean, but this is not a problem i had until recently and i have ran nistune for several years now. The ecu ground, which is what i think might be a problem, has not changed since i originally connected the system.

[Matt]

This is for a Z31 ECU?

So you have both the laptop and Nistune running from the same power source and going into the same ECU?

Are you using a LC-1 or LM1/2?

If you are using the LM then if you power independently from the vehicle, and without connected to the laptop, do the AFRs change then?

Reason why I ask is there may be a ground loop affecting your AFR reading out of the innovate unit at a guess