Ok.....to Data log all you do is hit the round button on the AP3 when your driving. My suggestion is when you think its gonna do it....record the data to try and catch it so some of us can review the data. Then you will need download the AP3 program for windows or ios/Apple. Then you will hook up the AP3 to the computer after you download the Cobb program. Doing so allows you to transfer/copy bins or files to others so they can look at them to see if they can find any irregularities in your recording.