Mark Purdy received a P4 build with Di2 from a not-to-be-named customer. The P4 was not designed with Di2 wiring in mind, so this is going to take some 'customization'. Mark is at my studio now, and we'll chart his progress through the course of the build.
All this has to go on or in the bike. Mark's plan is to house the battery in the P4's water bottle since the P4 wasn't designed with dedicated Di2 mounts.
10:26: Filing the shift cable opening to fit the Di2 plug.
10:30: The cables and control box have to route through these holes somehow.
10:35: Shifter cable holes in the extensions were enlarged to fit the plugs.
10:38: That hole under the armrest has to fit a brake cable and a shift wire. These will be filed as well.
10:40: Mark trying to figure out where to put the control box. Those big plugs make it hard to route the wires internally.
10:55: Wire fed through handlebars. Brake cable run through backwards to be a guide for housing.
10:58: Cervelo's cable routing system, where the cables enter the top tube and hit a stop in the downtube (housed in that big hole) is, according to Mark, "an indescribable pain in the ass". But at least in this case he only has to run one cable through it.
11:05: Kitty already bored. Thanks for asking.
11:08: First brake lever installed. Shimano recommends putting heat shrink tubing over the plugs for waterproofing. Mark thinks there'll be a handlebar upgrade soon, so he's using electrical tape for now.
11:13: The TT version of Di2 has a splitter: one cable goes to the extensions, the other goes to the brake lever. Being able to shift in both positions is one reason why Di2 is well suited for TT bikes (and the insanely rich).
11:16: The insides of the shifter.
11:20: Kitty getting interested again.
11:23: One side done.
11:30: Front brake hooked up.
11:38: Second side done. Things are looking clean with the extra cable jammed back into the bars. Next Mark has to decide how to route the wires of the control box. He'll probably have to route it down the side of the downtube and into that big cable stop hole. It would've been cleaner to go through the top tube, but that would've required dremeling out the top tube quite a bit.
11:50: A notch will be filed out of the cable stop as well as the downtube to accommodate the wire.
11:58: Notch cut in frame.
12:00 Cable stop was filed out to be a wire guide.
12:07: Mark about to pull the cables and snap everything into place.
12:12: All in.
12:18: The rear brake will have to be completely set and adjusted before the crank goes on. The shift wire is at the left. It'll go up the side of the downtube and into the bottle.
12:25: Just 222 grams.
12:30: Adjusting the pads. And it's lunchtime.
1:07: Back from lunch. By the way, Mark is available at 414-731-5802 or email@example.com for mechanic work.
1:10: Brake cable all set, neatly tucked away.
1:14: Crank goes on temporarily so Mark can install the front derailer. It'll have to come off again to wire everything up.
1:20: The front derailer has a set screw that rests against a metal tab (the silver square at left).
1:28: Front derailer goes on. (Mark's front derailer setup article here.)
1:38: The battery will be bolted down with the water bottle bolts. The bottom of the water bottle will be cut away so it'll slip over the top as a cover.
1:42: The wire to the rear derailer is just barely long enough. Mark plans out the wire path.
1:50: The battery is in, just barely. It needs room to slide out, and a locking tab needs room to flip open. The extra mount protruding out of frame will be cut off.
1:55: This piece is called the B junction, and would normally replace the BB cable guide. Mark's going to cut off the mounting tab on top and tuck this away inside the bottle as well. Also, the first electronic whirrs of derailer movement were just heard.
2:02: All wired up, everything working.
2:05: Mark files a notch into the bottom cover for the shifter wire.
2:13 Notching the water bottle cage for the derailer wires.
2:20: Wiring all connected and routed. Time to adjust the derailers.
2:35: Spoke too soon. Taping down wires with guides supplied by Shimano. Mark also wants to make sure the inner ring won't rub the wires by the BB.
2:58: Mark spent a lot of time making sure the inner ring would clear the brake and the wiring. Now the chain's going on. Mark likes the grease that the chain comes with, and recommends keeping it on for as long as possible before lubing up with your usual chain lube.
3:05 Chain's on, and it shifts pretty damn well already. It's really cool to see the front derailer auto trim. As soon as the chain gets near it, it automatically sets itself.
3:19: Shifting all adjusted. Set the limits screws, then put the chain on the fifth cog, put the system in adjustment mode, and tweak it until it's quiet. And then you're done. Mark really likes setting the limit screws on Di2 – without a cable involved, it's a wholly independent adjustment.
3:29: Cutting the water bottle to turn it into a battery cover.
3:35 Bottle trimmed and mounted, battery hidden away.
3:42 Wrapping the bars, ear canals still impeccably wax-free.
3:55: The front end all cleaned up. Mark's solution is a whole lot cleaner than all the setups I saw at Interbike.
4:06: Bottom cover goes on, build is basically done.
4:30: Six hours later, all done. Once again, Mark is available at 414-731-5802 or firstname.lastname@example.org for mechanic work.