A picture of what you have is helpful. Here is a manual for that model: Rain Bird ESP-Si User Manual
However, I do not see the exact layout of wires for that model, a 6 instead of an 8 is on page 12. I would guess an 8 might be as follows, left to right, and how they connect to the Rachio.
- 24VAC — do not connect to Rachio, use Rachio supplied power adapter
- 24VAC — see 1
- COM — Rachio has more than 1 ‘C’ connector. If you have more than one wire, it does not matter if they are connected together or all separated (although, I personally would connect separately)
- MV — Master Valve/Pump. If you have one, connect to ‘M’ and it needs to be configured in your app
- zone 8 — 8
- zone 7 — 7
- zone 6 — 6
- zone 5 — 5
- zone 4 — 4
- zone 3 — 3
- zone 2 — 2
- zone 1 — 1