Thread: cheap OBD2 device

Im looking for the thread that talks about a $15 obd2 interface that is USB. Im looking for a cheap scanner because me and my grandfater are working on alternative fuels for vehciles and we need to measure engine nock and all the stuff that a OBD program can provide. Also i was wondering anter we get the fuel that were working on perfected I have a car pc that runs of of linux right now and i would like a program to have a virtual dashboard for it any suggestions. Also can anyone suggest free or cheap obd software for doing testing on the fuels ill be using my laptop with xp for it so i dont have to have a program that funs on linux initially. Thanks for you help i really appreciate it.