Applications Mazda 13B-REW
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.
Mazda 13B-REW (FD RX-7)
FD3S sequential twin-turbo rotary. Two rotors, four coils (leading + trailing), oil metering pump, 13B CAS. Race Core F7 has rotary support in rusEFI/FOME; trailing split is a first-class setting, not a wasted-spark hack.
Recommended: Race Core F7. Engine type rotary, 2 rotors, 4 ignition outputs, 2 (or 4 staged) injectors, oil metering on a spare low-side or a dedicated controller. Sequential twins need three solenoids.
- Cylinders: 2 rotors
- Displacement: 1308 (2 × 654) cc
- Firing order: Front leading → front trailing → rear leading → rear trailing
- Orientation: Front rotor toward the radiator, rear toward the gearbox. Leading plugs on the intake side, trailing on the exhaust side.
Variants
| Variant | Years | Trigger | Notes |
|---|---|---|---|
| 13B-REW FD3S | 1992–2002 | CAS (24+1 / optical class) or aftermarket 36-1 on eccentric shaft | Sequential twins, 8.5:1, 4 coils, primary + secondary injectors. |
| 13B-RE FC | 1986–1991 | CAS | Single turbo, similar coil layout, different twins. |
Recommended pin assignment (Race Core F7)
| Pin | TunerStudio | Function |
|---|---|---|
| B10 | Digital 1 | Eccentric-shaft / CAS (after conversion: 36-1 Hall) |
| B1 | Digital 2 | CAS inner / sync if still used |
| A3 | Lowside 1 | Front primary injector |
| A15 | Lowside 2 | Rear primary injector |
| A4 | Lowside 3 | Front secondary injector |
| A16 | Lowside 4 | Rear secondary injector |
| A35 | Ign 1 | Front leading coil |
| A34 | Ign 2 | Rear leading coil |
| A22 | Ign 3 | Front trailing coil |
| A33 | Ign 4 | Rear trailing 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 |
| A20 | Lowside 10 | Fuel-pump relay coil |
| A21 | Lowside 12 | Main-relay coil |
| A12 | Lowside 15 | Radiator-fan relay coil |
| A8 | Lowside 9 | Oil metering / air pump / spare |
| A14 | Highside 4 | Pre-control / wastegate / charge-relief solenoids (assign 3 outputs) |
| 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
Factory 13B CAS is an optical / multi-tooth disk on the eccentric shaft. rusEFI has rotary trigger support; a missing-tooth 36-1 on the eccentric shaft is the reliable Race Core path. Set engine type to rotary, 2 rotors — never ‘4 cylinder wasted spark’ to fake trailing.
Crank
| Recommended | 36-1 Hall/VR on the eccentric shaft. |
| Factory CAS | Possible with the rotary decoder if the disk matches a supported pattern. Photograph the disk; do not assume 36-1. |
Cam
| Rotary | No camshaft. Sync is on the eccentric shaft. A second track on the CAS is home, not a four-stroke cam. |
TunerStudio
| Setting | Value |
|---|---|
| Trigger / wheel type | Rotary decoder or 36-1, engine type Rotary, 2 rotors |
| Use only rising edge | VR: typically yes on MAX992x. Hall: as logged. |
| Invert primary | No — swap VR wires first |
| Firing order | Leading then trailing per rotor |
Offset: Lock leading at a known angle, light the front leading plug. Trailing split after leading is correct.
- Trailing split is degrees of retard from leading. OEM marks are often 5° ATDC leading / 20° ATDC trailing at idle — that is a split, not two independent maps on day one.
Injection
Primary injectors in the port, secondaries staged. High-Z on most aftermarket; OEM FD primaries/secondaries differ — meter them. Staged injection: secondaries on Lowside 3/4.
| Primaries | Lowside 1 front, Lowside 2 rear. |
| Secondaries | Enable staged injection. Do not run secondaries at idle. |
| Fuel | Return, 1:1. The OEM FD pump is tired. |
Ignition
Four logic coils: leading front/rear, trailing front/rear. Trailing wants a coil that can fire late without melting — OEM trailing coils are specific. Dwell 2.0–2.5 ms.
| Leading | Ign 1 front, Ign 2 rear. |
| Trailing | Ign 3 front, Ign 4 rear. |
| Mode | Rotary leading/trailing, not wasted-spark 4-cyl. |
Idle
BAC / ISC 2-wire PWM, plus sequential-twin valves that must sit in the idle position. A stuck pre-control valve idles on one turbo and looks like a vacuum leak.
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.