For all the complaints we have about tuning around OEM CAN-BUS systems, there's a good reason why its there.
CAN-Bus systems are essentially a means of multiplexing electrical signals in a car over a small number of wires. Instead of using a pair of wires running from the ecu to the far corners of a car to power every single bulb, switch and motor, signal multiplexing allows these systems to be controlled by just a few wires that carry all these signals. In a simplfied way, multiplexing works much like modern phone lines or ethernet cables where several signals and instructions are meshed together and carried on the same line. The main reason that OEMs use this isn't to make life difficult for us. It saves weight and more importantly costs.
For the same reason, we should be wiring our cars with systems like this. If you've ever pulled the entire electrical harness from a modern car, you'd know that there is close to 70-pounds of copper and plastic just in wiring. To get around this nightmare, Littlefuse, an OEM supplier of automotive fuses and electrical components have introduced their ISIS (Intelligent Silicon Integrated System) Multiplex System. This basically allows someone to control a whole slew of electrical systems from stereos, aftermarket lighting and security to airbag systems with a small programmable system. It can also be used as a stand alone system if you wanted to wire up an entire race car.
The ISIS system consists of at least one master cell and one power cell. Typically the master cell is located near the firewall where switches and controls are located. It communicates with one or several power cells located at different corners of the car through a small diameter insullated harness which is the only wiring that has to run from one corner of the car to the other. As long as the Powercell is also connected to battery power, it can drive up to 10 different electrical outputs with a maximum draw of 20 amps. This eliminates a lot of wiring and relays as everything is solid state driven and rated for automotive use.
The system is also very smart. All the control logic can be programmed in by the manufacturer so that different types of switches can be use with just about any imaginable output (soft start, flashing at programmable intervals, dimming, speed control, and analogue out.) A single switch input to the Master cell can also drive several outputs at two different Powercell outputs for headlight and tailight operation. Or several switches can be used to control one output like in the case of turn signals and hazard lights.
For the car show guy this has endless possibilities in terms of bells and whistles, but for the SCC guy, this would be the way to wire a race car for weight savings and simplicity of troubleshooting. The LCD display in the MASTERCELL and flashing LEDs in each CELL make trouble shooting wiring a simple matter. OEM level weather and noise insulation take care of longevitiy issues too.
While we look for a project car to put this to use on, find out more details at www.isispower.com