Introduction: Why the Apexi Power FC for the 13B-REW?

The Apexi Power FC remains one of the most respected standalone engine management systems for the Mazda RX-7 equipped with the 13B-REW twin-turbo rotary engine. Unlike a piggyback unit, the Power FC replaces the factory ECU entirely, giving you full control over fuel delivery, ignition timing, boost pressure, and auxiliary functions. For owners seeking to move beyond stock power levels—whether through upgraded turbos, larger injectors, or higher boost—the Power FC provides a stable, tunable platform that retains factory-like drivability when properly calibrated.

This expanded guide covers not only the physical installation but also the critical tuning steps, common pitfalls, and recommended supporting modifications. Whether you are a seasoned rotary enthusiast or a first-time RX-7 owner, following these steps will help you achieve a reliable and powerful setup.

What You Need for Installation

Before beginning, gather all necessary components and tools. A thorough preparation prevents unnecessary delays and ensures a clean installation.

Required Hardware

  • Apexi Power FC unit – Ensure it is the correct version for the 13B-REW (model PFC FD3S or equivalent).
  • FC Commander – Highly recommended for on-the-fly tuning and data logging without a laptop.
  • Wideband O2 sensor and gauge – Essential for accurate air-fuel ratio (AFR) readings during tuning (e.g., AEM X-Series or Innovate LC-2).
  • Boost controller – Optional but recommended if you plan to run more than stock boost (e.g., Apexi AVC-R or electronic boost control solenoid).
  • Basic hand tools – 10mm, 12mm wrenches, screwdrivers (Phillips and flathead), trim removal tools, and a multimeter for electrical checks.
  • Wire connectors, heat shrink, electrical tape – For any required splices (though the Power FC is largely plug-and-play, some installations may need signal wire connections).
  • Laptop with tuning software – Optional; the Power FC can be tuned via the FC Commander, but software like FC Tune or Data Logit provides more detailed maps and logging.

Supporting Modifications

To fully benefit from the Power FC, consider having these items installed beforehand or ready at the same time:

  • Higher-flow fuel pump (e.g., Walbro 255 lph or Bosch 044)
  • Larger fuel injectors (e.g., 720cc or 1000cc, depending on power goals)
  • Upgraded intercooler and intake piping
  • Aftermarket downpipe and exhaust

Pre-Installation Preparation

Safety and preparation are paramount when working with the RX-7’s electrical system. Follow these steps before touching any wiring.

Disconnect the Battery

Disconnect the negative terminal of the battery and isolate the cable. Wait at least five minutes to allow the factory ECU’s capacitors to discharge. This minimizes the risk of short circuits and airbag deployment.

Gather Factory Service Information

Have a wiring diagram for the 1993-1995 RX-7 (FD3S) handy. The Power FC is largely plug-and-play, but verifying pinouts can save time if you encounter a non-running condition. Many online resources like the RX7Club forum provide downloadable diagrams.

Clear Workspace

Remove the driver’s side floor mat, kick panel, and any aftermarket under-dash accessories. Ensure good lighting and have a small container for bolts and trim clips.

Step-by-Step Installation Process

Step 1: Remove the Factory ECU

The factory ECU on a right-hand-drive FD3S is located behind the passenger side footwell panel; for left-hand-drive models, it is on the driver’s side, above the accelerator pedal. Remove the lower dash panel and the metal bracket securing the ECU.

Unplug both main harness connectors (a gray 24-pin and a brown 26-pin, plus a single-pin connector for the check engine light). Gently pull the ECU free and set it aside.

Step 2: Install the Power FC Unit

Mount the Power FC in the same location as the factory ECU using the supplied brackets or double-sided tape. Some owners prefer to relocate it to a dryer location (e.g., glovebox area) to avoid moisture, but the factory location works fine if all seals are intact.

Route the main harness connectors from the Power FC to the factory harness. The connectors are keyed and only fit one way. Push firmly until they click into place. If your Power FC is a used unit, inspect the pins for corrosion or bent pins.

Step 3: Connect Optional Accessories

If you have the FC Commander, plug its cable into the port on the Power FC (usually labeled “COMM”). Mount the Commander on the dashboard or center console for easy access during tuning.

For boost control, connect the boost control solenoid wires according to the Power FC manual (typically yellow/white wires for the solenoid output). If you are not using a boost controller, leave these unconnected—the Power FC will not trigger any errors.

Step 4: Reinstall Panels and Reconnect Battery

Carefully tuck all wiring out of the way, ensuring no cables interfere with the pedals or steering column. Replace the lower dash panel and any trim. Reconnect the battery negative terminal. Double-check that all connectors are seated.

Step 5: Initial Power-On and Check

Turn the ignition to the ON position (do not start yet). The FC Commander should illuminate and display system status. Verify that the Check Engine Light (CEL) on the dashboard goes off after a few seconds (this indicates the Power FC is communicating). If the CEL stays on, double-check the single-pin connector for the CEL signal.

Step 6: Start the Engine

With the ignition on, turn the key to start. The engine should fire immediately on a base map (if the Power FC came pre-loaded). If it cranks but does not start, check for fuel pressure (confirm the fuel pump primes with the key on) and spark. For more detailed startup troubleshooting, see the Common Issues section below.

Tuning Your 13B-REW with the Power FC

Tuning is where the Power FC truly transforms the RX-7. A stock 13B-REW running a base map will run, but performance and safety will be compromised without proper calibration. Follow these guidelines to build a reliable tune.

Fuel Mapping

The Power FC uses a load map based on RPM and intake pressure (MAP sensor). Start by setting a safe, rich AFR target (10.5:1 to 11.0:1) for boosted areas to prevent detonation. Use your wideband O2 sensor to log AFRs while driving. Adjust the injector pulse width in each load/rpm cell to achieve the desired AFR. Always tune on a conservative timing curve first.

Ignition Timing

Rotary engines are sensitive to knock. Set ignition timing to approximately 15-20 degrees BTDC at idle and 8-12 degrees at peak boost (15-20 psi) on a stock-port engine. Retard timing as boost pressure increases. Use Apexi’s official Power FC software or FC Tune to view and modify the ignition map.

Boost Control

If you connected a boost control solenoid, you can set target boost pressure in the Power FC’s boost control menu. Start with a conservative 10-12 psi on stock turbos, or 15-18 psi on upgraded turbos (depending on fuel octane and cooling). Boost targeting is duty-cycle controlled; begin with a 40-50% duty and adjust up to reach the desired boost, monitoring for spikes.

Data Logging and Fine-Tuning

Use the FC Commander’s logging feature or connect a laptop to record knock counts, AFR, intake air temperature, and exhaust gas temperature. Street tuning is possible, but a professional dyno tune is highly recommended for safety and maximum power. Many rotary tuning specialists work with the Power FC and can provide a custom calibration.

Common Issues and Troubleshooting

Engine Cranks but Does Not Start

  • Confirm that the Power FC is receiving power and ground—check the constant 12V (red wire) and switched 12V (white wire) at the main relay.
  • Ensure the factory main relay is functioning. The Power FC requires the same relay signals as the stock ECU.
  • Check for spark by pulling a leading plug and grounding it while cranking. No spark indicates a faulty igniter or Power FC output.
  • If the fuel pump does not prime, verify the fuel pump relay circuit (Power FC pin 2F on the 26-pin connector powers the FP relay).

Check Engine Light Stays On

On the Power FC, the CEL illuminates for certain sensor faults. Use the FC Commander to read diagnostic codes. Common codes include:

  • Code 12: “O2 sensor” – The factory O2 sensor is not used; ignore this if you are using a wideband.
  • Code 34: “Air pump” – The power FC expects a signal from the secondary air pump; a resistor can be added to mimic the load.
  • Code 55: “Knock sensor” – Check the knock sensor wiring and torque; it often triggers due to vibration.

Idle Surge or Stalling

Improper idle speed adjustment (target 750-800 rpm for a street port) or vacuum leaks are the usual causes. Ensure the idle air control valve (IACV) is functioning. The Power FC’s idle speed control can be adjusted via the “ISC” menu.

Boost Spikes or Overboost

If using the Power FC’s internal boost control, the solenoid duty cycle may be too high. Reduce duty cycle and increase the wastegate spring pressure if possible. Alternatively, use an external boost controller for more stability.

Conclusion

Installing an Apexi Power FC on your 13B-REW opens the door to substantial power gains and refined drivability, provided the installation is methodical and the tuning is thorough. By following the steps above—preparing the workspace, correctly wiring the unit, and dedicating time to fuel and ignition mapping—you can transform your RX-7 into a well-controlled, responsive machine. For in-depth support, consult the Power FC section on RX7Club or Apexi’s official support page. Remember: a safe tune is a fast tune—invest in quality components and professional guidance if you are new to standalone engine management.