CAN allows for data packets with a payload of up to 8 bytes, to send messages longer than 8 bytes it is necessary to use a transport protocol. The OBD-II specification for example makes use of ISO-TP (ISO 15765-2). Volkswagen however uses it's own transport protocol in its vehicles, known as VW TP 2.0.
VAG Blocks is open source (GPLv3) beta software for reading VAG group specific measuring blocks from an OBD-II port using an inexpensive ELM327 type adapter. Both Bluetooth and USB adapters have been tested on Windows & Linux. Sample rates of up to 12 samples per second have been achieved.
Various control modules are supported such as the engine ECU and gearbox. Values such as boost, oil temperature, DPF soot loading and current gear can be plotted in program and logged to a CSV file.