Applications Subaru EJ20
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 EJ20 / EJ25
WRX/STI. Crank 36-2-2-2, AVCS on later, wasted-spark or COP. Firing order is not 1-3-4-2.
Recommended: Race Core F7. Four sequential, COP conversion preferred, 36-2-2-2 decoder — not 36-1.
- Cylinders: 4
- Displacement: 1994 (EJ20) · 2457 (EJ25) cc
- Firing order: 1-3-2-4
- Orientation: Boxer. Cylinder 1 front-right from the driver’s seat on a typical WRX. 1+3 right, 2+4 left.
Variants
| Variant | Years | Trigger | Notes |
|---|---|---|---|
| EJ20G / EJ20K | 1994–2000 | Subaru 6/7 crank+cam or early pattern | GC8. Waste spark. Confirm the wheel — early is not 36-2-2-2. |
| EJ205 / EJ207 | 1999–2007 | 36-2-2-2 class + cam | GD WRX/STI. COP or waste spark. AVCS on later STI. |
| EJ255 / EJ257 | 2004–2014 | 36-2-2-2 + AVCS | GR/GV. Dual AVCS on some. DBW on later USDM. |
Recommended pin assignment (Race Core F7)
| Pin | TunerStudio | Function |
|---|---|---|
| B10 | Digital 1 | Crank Hall |
| B1 | Digital 2 | Cam Hall |
| B11 | Digital 6 | Cam 2 / exhaust 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 |
| 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 | Knock 1 | Knock bank 1 |
| C35 | Knock 2 | Knock bank 2 |
| A20 | Lowside 10 | Fuel-pump relay coil |
| A21 | Lowside 12 | Main-relay coil |
| A12 | Lowside 15 | Radiator-fan relay coil |
| A2 | Highside 1 | VVT bank 1 / intake |
| A1 | Highside 2 | VVT bank 2 / exhaust |
| 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 − |
Trigger
Late EJ is 36-2-2-2. TunerStudio: 36-2-2-2 / Subaru — not 36-1. Early GC8 may be 6-tooth crank + 7-tooth cam (SUBARU_7_6). Photograph the crank reluctor.
Crank
| GD/GR | 36-2-2-2 Hall or VR at the crank. Digital 1 or VR 1. |
Cam
| AVCS | One or two cam Halls. Digital 2 / Digital 6. |
TunerStudio
| Setting | Value |
|---|---|
| Trigger / wheel type | 36-2-2-2 (late) or Subaru 7+6 (early GC8) |
| 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 on most WRX). Confirm which plug is #1 before you move offset 180°.
- Boxer #1 is not where a 2JZ #1 is. Use the factory cylinder numbers stamped on the heads.
Injection
High-Z on most, sequential four. Top-feed vs side-feed across years.
| Fuel | Return on older, returnless on later — add a return for boost. |
Ignition
COP on later STI (Ign 1–4). Early wasted-spark igniter.
| Dwell | 2.0–2.5 ms COP. |
Idle
Stepper on some, 2-wire on others, DBW on late USDM. Identify the throttle body.
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.