Discussion and questions related to the course EFI Wiring Fundamentals
Not to be controversial, but just an honest question. I have been lucky enough to do some electronics troubleshooting work on a wide variety of high end machines - factory S2000 rally cars, GT3 cars (circa 2015), LMP900 and LMP2. These cars all had harnesses built by the top names in the industry (I won't name them here).
Yet, most of the harness branches were not concentrically twisted (that's if anything at all even was), and in places that there were, no filler wires, breakouts at branches not that clean, no kapton tape in sight (PTFE tape used instead), and I could go on. All the "rules" showcased by excellent builders on Instagram and other places seem to be absent. The only consistent "rule" in these harnesses is that all connectors are autosport, and everything is booted and epoxied. Surely these manufacturers of high end harnesses for top level cars would apply every trick in the book?
So I guess my question is, how necessary are all the photogenic harness tricks you see online?
I'm with you on this front Paul, I've worked on a few GT3 and lower tier single seat cars also, and can back up most of what you've mentioned, except that the majority of harness sections on the single seater gear in particular were concentrically twisted, and filled out t have a circular cross section.
The PTFE tape is a really good substitute for kapton tape, and actually has some benefits, as it can be molded to the shape of the branch easier. Its there to stop the potting / exoxy compound from locking the wires together, making servicing all but impossible in the future. Its got the required temp rating, and in many respects is much nicer to work with than kapton tape.
Breakout points are always tricky to keep tidy, and you wont find too many photos online of people showing an un-booted breakout point, as they never look as impressive as the concentrically twisted section that leads up to it.
It's certainly part of what I'm trying to get across in the course material we've released, and are currently working on. You can do a really great, professional and reliable job of building a wiring harness, without needing to spend megabucks on tooling and materials, and the build taking over your entire life fora month or more.
That being said, you know what I get asked about the most? Concentric twisting. How to design the layers, how to undertake the process. I do believe it offers some benefits, particularly in a harness that enters the engine bay of a vehicle and needs to be handled when the vehicle is serviced... But for an interior body harness? I'm not going to recommend to a client that they pay the extra labor charges involves to have that harness twisted, when it is likely to remain in place for almost the life of the vehicle.
Excellent, I'm glad you have also seen this, at least on saloons. Have not done any single seaters myself, although I may be doing some work on a Formula Renault 3.5 soon.
Interesting thing you mention about the engine bay, this is where I mostly see the main trunk being concentrically twisted, and I guess you are right, it is for flexibility and reliability when installing/removing the engine.
I was a bit miffed to find out about the PTFE tape trick after buying an expensive roll of Kapton!
I just completed an engine loom for a little sports prototype tonight, and due to the tight confines of the engine bay, and the fact the loom has to make some tight twists, I did curse my way through twisting it neatly, with M27500 and 4 different gauges of M22750.Not much fun was had.
Add me to the list of people who would love some do's/don'ts about designing the layers for concentric twisting - where to put signal and power/ignition wires, how to approach having multiple gauges and wire types in one loom, etc.
When talking about PTFE - are we simply referring to plumbers tape?
Ben - Yes indeed :-).