Thanks for the link Thomas, I'll check it out.

You are correct about the amount of PID's to poll; having even 15 would slow the system down considerably, however CAN is much faster than J1850.

The PID's above will be used for polling or data logging, but not all for displaying necessarily. Some of the
critical parameters such as fuel pressure, tachometer, oil pressure, manifold pressure will be polled by the
LCDi box in real-time.

CAN bus will be used for the more basic items that don't need immediate attention like ECT, Fuel level, and
turn signals to name a few.

Sending CAN messages is not a problem. You can do pretty much anything to a device that's connected to
the network. With my little adventure programming the Ford GT's, we would poll several devices for information
and test the horn, individual lights, turning on the A/C, etc., directly from a laptop.

Essentially, everything you interface with (buttons, switches, levers) as the driver is not connected directly
to a piece of hardware. If you press the A/C button, the computer checks whether you pressed the button
and reads it as a CAN message.

The computer then interprets that message as a request and sends the appropriate command to the
corresponding output. It's a crazy system and I often ask myself why a simple light couldn't be
connected with a wire and a switch...there doesn't seem to be any reduction in vehicle wiring using CAN.