Applications Subaru FA20
Draft. Trigger offset has not been confirmed on a running Race Core install. Pins marked TBD are unknown — do not guess them. A wrong decoder or firing order can destroy the engine.
Subaru FA20
2.0 L FA boxer. BRZ / GT86 / GR86 FA20D is Toyota D-4S: port injectors plus direct injectors. WRX FA20DIT is direct injection. rusEFI’s 36-2-2-2 mode is the same family the EJ20 note uses for late EJs, and the public trigger list says that pattern is also used on some later Subarus. Firing order on the FA20DIT sheet is 1-3-2-4. Race Core drives port injectors only.
Recommended: Race Core F7. Four logic coils, AVCS, DBW. On an 86/BRZ, wire the port injectors and leave the direct injectors disconnected. On a WRX FA20DIT there is no port rail from the factory — fit one, or this ECU does not fuel the engine.
Status: draft. Trigger offset has not been confirmed on a running Race Core install.
- Cylinders: 4
- Displacement: 1998 cc
- Firing order: 1-3-2-4
- Orientation: Firing order 1-3-2-4. Cylinder 1 is the front cylinder on the right-hand bank, the same convention as the EJ20 note. Right-hand drive does not renumber the case. Confirm on the coil cover, then light that plug.
Variants
| Variant | Years | Trigger | Notes |
|---|---|---|---|
| FA20D 86 / BRZ | 2012–2020 class | 36-2-2-2 class | D-4S. Port injectors are usable. Direct injectors are not. DBW. AVCS. |
| FA20DIT WRX | 2014–2021 class | 36-2-2-2 class | Direct injection only from the factory. Port kit required. 1998 cc, firing 1-3-2-4. |
Recommended pin assignment (Race Core F7)
Pins below are the library default Race Core F7 map — the same AMPSEAL landings as the verified 1UZ-FE, 2JZ-GTE and LS1 notes. Core EFI V4 and Micro Core cavity numbers are TBD. If a pin is not in this table, it is TBD. Do not guess a spare.
| Pin | TunerStudio | Function |
|---|---|---|
| B5 / B13 | VR 1+ / VR 1− | Crank, if the sensor is 2-wire VR |
| B10 | Digital 1 | Crank, if the sensor is 3-wire Hall |
| B4 / B12 | VR 2+ / VR 2− | Cam VR |
| B1 | Digital 2 | Cam Hall |
| A3 | Lowside 1 | Injector cylinder 1 |
| A15 | Lowside 2 | Injector cylinder 2 |
| A4 | Lowside 3 | Injector cylinder 3 |
| A16 | Lowside 4 | Injector cylinder 4 |
| A35 | Ign 1 | Cyl 1 logic coil |
| A34 | Ign 2 | Cyl 2 logic coil |
| A22 | Ign 3 | Cyl 3 logic coil |
| A33 | Ign 4 | Cyl 4 logic coil |
| A2 | Highside 1 | Cam oil-control valve (PWM) |
| A1 | Highside 2 | Second oil-control or lift solenoid |
| B7/B6 + B15/B8 | ETB 1 ± / ETB 2 ± | DBW motor. Not a stepper as well. Pedal and TPS tracks: follow the APP and ETB notes |
| C20 | Analog Temp 3 | CLT |
| C30 | Analog Temp 2 | IAT |
| C13 | Analog Volt 1 | MAP 0–5 V |
| C24 | Analog Volt 2 | TPS 1 |
| C34 / C35 | Knock 1 / Knock 2 | Knock, one per bank |
| A20 | Lowside 10 | Fuel-pump relay coil |
| A21 | Lowside 12 | Main-relay coil |
| A12 | Lowside 15 | Radiator-fan relay coil |
| B17 / B16 | CAN 1 H / L | Dash / wideband |
| B18 | Battery Sense | Ignition-switched 12 V (5 A fuse) |
| B23 | +12 V MR | Main-relay 12 V into ECU |
| A17 A18 A24 B14 B19 B20 | Power GND | Engine block → battery − |
| C9 / C21 / C32 | 5 V Sens 1 | MAP, TPS, pedal 1 |
| C1–C8, C29, C31 | Sensor GND | 0–5 V and thermistor returns |
Trigger
Read the EJ20 note’s late-EJ section. Select 36-2-2-2, not 36-1 and not the early GC8 6+7. Confirm the composite shows two missing pairs, not one.
Crank
| Pattern | 36-2-2-2. Hall on Digital 1 or VR on VR 1, matching the sensor. |
Cam
| AVCS | Cam Hall on Digital 2. The second cam input is TBD. |
TunerStudio
| Setting | Value |
|---|---|
| Trigger / wheel type | 36-2-2-2 |
| Use only rising edge | VR: typically yes on MAX992x. Hall: as logged |
| Invert primary | No — swap VR wires first |
| Firing order | 1-3-2-4 |
Offset: Light on cylinder 1 (right-front). 180° out on a boxer is a bent engine, same warning as the EJ note.
Injection
Port injectors only, high-Z, sequential four. Direct injectors — the second set on D-4S, the only set on DIT — do not connect to a low-side.
| 86 / BRZ | Four port injectors on Lowside 1–4. Direct rail undriven. |
| WRX DIT | No start until a port rail exists. |
Ignition
Four logic COP, Ign 1–4 by cylinder number. Dwell 2.0–2.5 ms. Firing order 1-3-2-4 in software, which is not the inline-four 1-3-4-2.
| Order | 1-3-2-4. Do not load a Honda or Toyota four-cylinder firing order. |
Idle
DBW. F7 H-bridges, ETB and APP notes. No stepper. AVCS solenoids on the two high-sides — label intake left and right before they move.
First start
- Load the matching variant configuration in TunerStudio before the harness is live — injectors and coils stay disconnected until the decoder is confirmed.
- Fuel pump fuse out. Coils unplugged or spark outputs disabled. Crank. Open Diagnostics → composite / high-speed logger.
- Confirm crank teeth are even, the missing-tooth (or named pattern) is a single clean gap, and cam is one pulse per two crank revolutions for sequential four-stroke.
- RPM during cranking should sit in the 150–350 rpm band. 0 rpm or 12,000 rpm means the decoder is lost — polarity or wheel type, not offset.
- Lock timing to a fixed 10° (idle control off). Timing light on cylinder 1. Change trigger offset until the damper agrees with 10°.
- Recheck at ~3,000 rpm. If timing walks with RPM, it is VR polarity, a delayed Hall, or the wrong decoder — not offset.
- Enable spark. Confirm a healthy burn (timing light or plug colour) with fuel still disabled.
- Enable fuel. Prime, then crank. Catch the first idle on a rich-safe VE, then lean toward stoich at idle.
- Only then enable closed-loop idle, VVT, boost and traction. A base map is a starting point, not a dyno tune.
A base map is a starting point, not a dyno tune.