The EW-WU101 D-fly allows your Di2 system to communicate wirelessly with your head unit and smartphone or tablet. It'll let you display currently selected gears, allows you to switch head unit screens, update firmware, change settings and more.
It is generally placed on road bikes, positioned somewhere outside the frame, or in your handlebars. Have a look at the attached user manual for examples on where to place this unit on your bike.
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The unit has two e-Tube ports, allowing it to be placed between the rear derailleur and junction B. It is meant to be installed on the seat stay, close to the rear derailleur.
The EW-WU111 / EW-WU101 wireless units are meant to be used with the BT-DN110 / BM-DN100 battery/mount and will not work with the older SM-BTR2, SM-BMR1 or SM-BMR2 batteries. The older SM-EWW01 will work with the older batteries, but only supports ANT+ (no BluetoothLE).
In order to connect the Wireless Unit to your mobile phone you will need either the E-Tube Project mobile app or the E-Tube RIDE app. The latter is meant to be used on E-Bikes, but it'll work on up-to-date road bikes too. Note that if you have never updated your Wireless Unit then it will only work with E-Tube Project.
Pairing a Garmin is relatively simple. The video below shows the process on a Garmin EDGE 830.
The same can be done on a Wahoo ELEMNT device:
And of course, plenty of other bike computers: Sigma, Lezyne, Bryton, Mio, and others all support Di2. You generally add the Di2 system through the sensors menu / page.
Di2 road bikes do not feature wireless communication by default. You need a Wireless Unit or D-fly in order to add BluetoothLE / ANT to your bike. You can then control your Garmin/Wahoo and see di2 stats and gearing information on your head unit.
There are many possibilities for installing the EW-WU111 Di2 D-Fly Wireless Unit. This guide explains how to do that.
This complete wireless (BluetoothLE / ANT) Troubleshooting guide will answer your setup questions and help you overcome your BluetoothLE/ANT troubles.
The Di2 D-Fly or Wireless Unit is a great piece of kit. However, the forced wireless update doesn't always work and *can* crash the entire bike. If that happened to you, read how to fix that right here!
