Coil harness
Here are some coil harness details. Again the finished harness:
I went down a bit of a rabbit hole with this thing. It is the biggest harness I've made, so I figured I would use it as a way to understand proper wiring bits and techniques. There is a lot to wiing, more than expected, especially if you want to build "motorsports grade" harnesses. I'd say the harness I made is probably 60% of the way to full motorsports harness. If I wanted to go all in -- use all the fancy connectors, properly concentric twist, have strong opinions on my shrink tube -- I'd probably need to rewire the whole engine.
Even this little thing was time consuming and expensive. I'm in it at least 10 hours and $250. I overbought as usual, but if I were efficient, it's still $160 in parts.
Schematic
You probably saw the the schematic in the last post. Here it is again:
It's pretty simple: each coil has 3 wires, 12v power, ground, and signal.
12v power and ground comes from a VSS patch harness. The VSS 12v and ground wires are directly connected to all six coils.
The signal pin on each coil is connected to one pin on the engine harness' igniter plug.
Wire
The first rule of fancy harnesses is tefzel ("mil-spec") wire, so thats what I used. I have mostly used TXL/GXL wire in the past, but tefzel is what the cool kids use. This
prowireusa page is a pretty good explainer on tefzel. The tl;dr is that there are really two kinds of tefzel wire: M22759/32 and M22759/16. /32 has less insulation than /16, otherwise they are the same. /32 is more desirable (and expensive) cause it is lighter and takes up less space.
Another thing I learned is that most "mil-spec" harnesses use really small wire, 22 awg is the norm. My foundry 3 coil harness uses 22 awg /32 tefzel, and maybe it's sufficient. I ended up going with bigger 16 and 18 awg wire, though, for a couple reasons:
1. The factory Honda (sumitomo) connectors in this harness are made for 14-18 awg wire. Likely the reason the crimps were so crappy on the foundry 3 harness is that the terminals are pretty big and the wire is tiny. Hot dog down a hallway, not ideal.
2. I want the harness to have high current carrying capacity. Good power to the coils is more important than saving 5 grams in wire weight.
I ended up with a mix of /16 and /32 wire because they were out of stock of /32 in some colors. Here's a comparison of 18 awg wires: /32, /16, and TXL:
Sleeve
Sweet, I have wire, now how to cover it?
Cool-kid mil-spec harnesses don't really use sleeving, they just use shrink tube, specifically Raychem DR-25.
The Foundry 3 harness did use sleeving, techflex flexo (I think), which is rated to 125C.
I got a bunch of different sleeving from Prowire, and liked the
techflex Insultherm the best. It's super high temp (1200F), flexible, expandable, doesn't fray, and I don't have to cut if off (like shrink tube) if I need to fix something in the harness.
BOM
Here are all the bits I ended up using in the harness:
Cycleterminal:
* 6x HX 090 3 pin female connectors for each coil ($6 each)
* 1x HW 090 6 pin male connector for coil signal ($4 each)
* 1x HW 090 3 pin male connector VSS patch ($3.50 each)
* 1x HW 090 3 pin female connector VSS patch ($3.50 each)
* 4x splices 3x16 awg ($1)
* 2x splices 4x18 awg ($1)
Prowire USA:
* 13 ft red 18 awg ($1.25 / ft)
* 13 ft black 18 awg ($1.40 / ft)
* 2 ft red 16 awg ($1.50 / ft)
* 3 ft black 16 awg ($1.50 / ft)
* 18 ft 18 awg for coil signal (3 ft in 6 different colors) $1/ft
* 3 ft insultherm 1/4" (size 2) ($0.85 / ft)
* 1 ft insultherm 5/32" (size 6) ($0.50 / ft)
* 5 ft insultherm 1/8" (size 9) ($0.50 / ft)
* 1x shrinky tee booty thing ($14)
* 1x numbered shrink 6 cyl ($2)
* 1 ft non-adhesive clear shrink ($10)
* Adhesive-lined shrink tube (I bought a Raychem 4:1 kit with 5 different sizes) ($40)
* 1/2" Kapton tape ($11)
All this stuff is not cheap. I'm in this thing about $160 just in parts, I overbought. I now understand why a "mil-spec" Rywire engine harness is like $500 - $1k.
Building
I started by doing a bunch of measuring of the distance between the left side coils (cyl 3 & 6). My harness passes under the intake manifold. All power wires for all coils are spliced together, so 3 long wires between the coils for power, then the same for ground. The power wires:
I mocked them up in the engine bay 10 times to make sure it'd all fit:
I spliced all the grounds together, and all the power wires together along with wires down to the VSS
Skipping a lot of steps, here are all wires mocked up and twisted:
These are just twisted, not a proper concentric twist. A real concentric twist only really works with specific number of wires and takes a lot more planning. So either I'd have to add some filler wires in there, or a slightly gruntier twist. I opted for the latter.
Next up was taping up parts of the harness to keep the wires together before adding the sleeve. Fancy harnesses don't use black electrical tape, they use Kapton tape:
I taped every junction and split just to keep everything in the right spot. I put the most tape on the coil signal wires. I also got this cool shrink tube tee thing.
After the junction points were taped up, I sleeved everything. It was a bit tricky getting the order of operations right when installing the sleeve. The general rule was, largest sleeve went on first, so I worked from the center out.
Here's the shrink boot tee around the Insultherm:
Then after all the sleeve was on, I added the terminals and the connectors.
The end
And it works, yay. I took the car out for a super long drive this weekend and it performed perfectly. The car still has some small quirks, of course, but I don't think they are ignition harness related anymore.