I started working on the wiring diagrams for the GTM about 2 months ago. A little thing called work got in the way. Over the past couple days, I have had a chance to concentrate on this project. I am using ISIS Power for my wiring. ISIS is an intelligent multiplex system that does not rely on traditional relays, fuse boxes or fixed functionality. It is simple and flexible.
The brains of the ISIS system is the Master Cell. All inputs to the electrical system go here and are distributed to the appropriate Power Cell. The Power Cell in turn directs current to connected peripherals. Instructions are passed between Master Cell and Power Cells via data bus (the data bus is represented by the heavy red line in the drawings). Power leads are run from the battery/fuses to each Power Cell. This eliminates the need to run high current through the inputs and switches. Signal input from switches to the Master Cell is measured in milliamps.
Major Wiring Diagram.
Based on all the peripherals I plan to incorporate and using the GTM standard worksheets as a starting point (these are the base set up sheets for a GTM available on the ISIS website), I mapped out the number of cells I need to run everything in the GTM. NOTE: This wiring is independent of the engine harness. These are the ISIS components:
Master Cell with InTouch Mobile interface card. Location: Forward firewall.
(3) Power Cells. Location: (2) forward firewall, (1) rear firewall
InMotion Cell, Location: Forward Firewall.
InTouch Console: Double Din center console.
InDash: Behind driver's dash board.
Mirror Controller: Forward firewall.
InMotion Cell handles bi-directional items like windows and telescoping steering column.
ISIS is coming out with a unit dedicated to controlling the side view mirrors. I presume it will be priced below an InMotion cell.
Power Cell 1 reflects basic ISIS programming for the GTM. These peripherals are all located forward.
Power Cell 3 is an addition to the basic 3 cell starter kit. It manages most of the additional electronics I plan to add.
Power Cell 2 is located in the rear engine compartment. It reflects basic ISIS programming with the addition of the seat heaters.
I'm at the South Carolina house, and Labor Day Weekend has afforded me the time to start laying out the circuits for the GTM. When I decided to tackle this project, I never considered how much of it involved wiring. After spending the long weekend reading up on ISIS, I am convinced the ISIS Power system does significantly cut the time and complexity for wiring portion of the car.
If you have been around an iPad, iTouch, iPhone or Droid, I'm sure you've figured out that Apps are all the rage these days. Key fobs have eliminated the need to fumble with a door key. If you've had a chance to see late model Corvettes, Ferraris or even our Toyota Camry, they use a button to start the car.
So ISIS takes it another step further (they're probably not the only people doing this) and eliminate the key fob and the key. The ISIS inTOUCH system mounts an encrypted WIFI daughter board on the Master Cell. (The Master Cell is the central brain for the ISIS system.) You then download an app from iTunes or the Droid Marketplace (the Droid App is due out in late 2011) to your Apple or Droid device, and load the encryption key to the app. It can unlock the car, turn the lights on or roll down the windows. Actually, you can set up the programming to do just about anything you want.
If you still want a key fob, they'll sell you last century's technology with their inLINK system. It operates on the same principle of mounting a daughter board on the Master Cell and using radio frequency technology.
The cost difference is $70 and you end up with a much cleaner interface.
The project I am currently working on involves updating the front end of the Boxster. One aspect of the new look is the addition of DRLs (daytime running lights) that I purchased from Pedro's Garage. For you Boxster enthusiasts, this is a great site for do it yourself projects.
To get power to the DRLs, I have to tap into the windshield wiper motor. Sounds simple, until you look at all the wires running to and fro just for the wiper motor. Fortunately, I have a multimeter and a very good after market manual. There are several pages devoted to schematics of different electrical systems. As my eyes begin to glaze over, I realize that wiring the GTM could be the hardest part of the build.
So I asked people who have wired cars. My wife's cousin, Tim, has restored several classic cars (and a few other odds and ends) told me to check out American Autowire. If I had a classic Mustang or Corvette that required rewiring, this certainly is the system I would use. However, this is a GTM that I plan to install just about every electronic gadget known to man.
Then I stumbled across the ISIS Multiplex System on the Factory Five Forum. This system might also be referred to as ISquare, 1 + 1 or LittleFuse. ISIS is a modular and scalable electrical system that that manages the lights, signals, dash gauges, electronics, ignition, battery monitoring, electric windows, door poppers (well you get the idea).
Rather than stumble through a poor explanation, I found 4 videos produced by Two Guys Garage. The best part of these videos, they explain the ISIS system and they install it on a GTM!
These videos are about a year old.
Since then, they have added the inMOTION Cell. This module handles item like door poppers, power windows and anything where reverse polarity is necessary to make something run. It manages 5 devices instead of 10 like a regular power cell.
The other addition is the inTOUCH MAX Double DIN Touch Screen. With the exception of turn signals and hazard lights, every switch on the dash can be managed from this touch screen module. Plus you can password protect the car, in addition, the security already built into the master cell. The next video shows an actual install.
I talked to Jay Harris, President of ISIS Power last week. He answered a few more questions:
LED lights, flashers - no problem. All of that is managed through the master cell and there is no reliance on electro-mechanical flashers.
The different cells are daisy chained via a data cable enclosed in wire loom. On a build like the GTM, there is no order dependence for cells.
Back up cameras are not currently supported by the inTOUCH cell. Jay plans to support cameras via inTouch by first Quarter 2012.
Custom programming can either be done at the factory, or you can do it yourself.
There is lots of info and reference material on the ISIS Power Site.
This is a modular and scalable system that even a computer geek like me can figure out.
Down side: it will cost more, and I will not be using the supplied wiring from the kit.
