Originally Posted by BGTV8

You need the following mapped by track position for relative lap analysis:
1. Steering angle
2. Brake pressure
3. Throttle %-age
4. Speed

I have both RacePak and Motec (2 different cars) and whilst I started my data journey with Haltech ECU and RacePak logger dash in my old race car, I found Motec in my Z34 to be more complex to set up but in the end it should be easier to use as I don;t have the overheads of setting up track maps and I have access to a lot of target lap time data from other cars to measure myself against.

There are phone app's you can use as well but these will rely on OBDII and bluetooth and can be laggy and you are at the mercy of what the ECU is seeing.