A major portion of the work I'm carrying out on the v6 is the replacement of the OEM loom with something a little lighter and less complex. There's some solid "pros" for doing this...
1) Any OEM loom is always a compromise between cost, time to fit & generic use (i.e. applies to multiple models)
2) In my specific case there's so little left in the car that I'm driving around with a loom which is probably getting on for 75% redundant
3) Integrating new functionality with an OEM loom is prone to many challenges and potential impacts on reliability
But of course there're also some big cons...
1) It's complicated to rewire an entire car especially if you've never done it before
2) Cost can be high, with no discounts for volume that the OEM enjoys, the cost of wire, connectors, fuses etc can quickly mount up and don't even think about the costs of some of the tooling required (£90 for a crimper for battery terminals for example)
I've already bought, read and digested a bunch of books on the subject of automotive wiring ranging from text books through to specific books about Competition car electrics so I've a good idea of the theory side of how to wire the car but actually doing it for real presents some choices; decisions that need to be made now rather than when I'm 50% of the way through the project so this post is really about an insight into my decision process...
Convention dictates that a car loom is normally comprised of relays for switching high current loads, fuses to protect the loom itself, switches to actually turn bits on and off and of course special components to deliver things like indicators, hazard warning lights, wiper motor control. Typically a loom is logically divided into different parts according to function; so you have a charging circuit, a lighting circuit etc.
My initial decision was to go with convention but also to wire to "competition" spec; this would mean circuit breakers instead of fuses, Raychem or similar wiring, Souria aerospace connectors (i.e. milspec), high current toggle switches and solid state battery isolation. This is, in no way, the cheap option but would in effect produce a FIA compliant wiring loom and would look "spangly" too!
Then a chance conversation with Scott and a follow up with TRW1 led me to look at the MoTeC PDM technology. PDM does away with the need for fuses or circuit breakers, allows you to use low current wiring for switches, adds logic operations so that you can, for example, implement indicators or hazards purely in "software" - in short it's very clever and will make the wiring job much simpler but...it's MoTeC and that means it's not cheap in fact the harsh reality is that I don't "play" at the level where I can justify dropping the 2.5 to 3k on the technology (and don't forget I'd still need to buy wiring, switches etc).
So off to Google then because a) it's must be cheaper in Australia b) the Chinese must be producing something similar with a slight increase in the risk of fire etc or c) someone else must have come up with a similar system. What I quickly found was that...
1) It's not cheaper, anywhere else
2) It's not expensive compared to Pectel
3) There's an equivalant made in this Coutry by Add Engineering called IPU16 but..it's the same cost
4) Everybody who uses it thinks it's the best thing since sliced bread
Then, by accident, I found the website of ISIS (
http://www.isispower.com/index.html ). Their solution is sort of halfway between the "old" way and the new way of PDM, IPU etc. It offers many of the advantages of the MoTeC technology, and in some cases expands upon what PDM can do, but crucially it's much, much more affordable. There's a video on their home page of the technology being demonstrated at SEMA - if you have, even a passing interest in this area of motorsport, watch it - the technology is very impressive and if you like the idea of being able to remote control you're entire car electrical system from an iPhone sized touchscreen then you need this system.
So then my decision is to go with ISIS - it's going to offer so many advantages to my specific application that I can justify the cost. They don't have a UK distributor...hmmm, I wonder if this is a business opportunity, but they proved to be very responsive over both email and the telephone so I'm not overly concerned.
Of course I didn't spend the entire weekend just thinking some practical stuff took place as well; I can confidently report that removing the last of the loom from under the car is a painful and frustrating experience. None of the parts that were supposed to "definitely be with you before the weekend, sir" arrived. Work began on creating the bucks for the center console and dash panels and hopefully by the end of the Christmas period I'll have these done ready to go off to the laminator. Tim helped me clarify my ideas around how to produce a bulkhead so that's probably the next thing to do and I will, honestly, take some more pictures.