04 Wiring
Ignition
5 V logic coils. Do not wire a dumb coil negative to Race Core.
6 min readUpdated 2026-08
Smart coil (recommended)
GM LSx truck coils, Denso pencil coils with a built-in igniter, Bosch smart coils, IGN-1A:
- Pin 12 V: main-relay 12 V, fused.
- Pin GND: cylinder-head / coil-bracket ground, not sensor ground.
- Pin signal: Race Core Ignition n (5 V).
- Pin 5 V (if present, some Denso): ECU 5 V or a dedicated 5 V, per coil datasheet.
Spark modes
| Mode | Needs | Notes |
|---|---|---|
| Coil per cylinder | Cam + one coil per cyl | Preferred. 12 coils max. |
| Wasted spark | Crank only | Paired coils fire together. Fine for first start on a 4-cyl. |
| Distributor | One ignition output + a distributor | Possible. Not why you bought a 12-coil ECU. |
Firing order is software. Wire coils in cylinder order, then set the firing order (e.g. LS 1-8-7-2-6-5-4-3, SR20 1-3-4-2, RB 1-5-3-6-2-4) in the ignition menu.
Dwell
Start conservative: 2.0–2.5 ms running, slightly more on crank if the voltage sags. LSx coils like ~2.5–3.0 ms. If the coil is hot to the touch after a 30-second idle, dwell is too long or the 12 V ground is poor.