Overview
The Apexi S-AFC II (Super Air Flow Converter) is a fuel management device that allows precise adjustment of air/fuel ratios by intercepting and modifying signals between the Mass Air Flow sensor and ECU. This guide covers installation on the Celica ST (AT200) with the 7A-FE engine.
🕒 Time Required: 2 hours
💰 Cost: $300-500 (S-AFC II unit)
🚗 Application: ST (AT200) with 7A-FE engine
Required Tools & Materials
Basic Tools
- Wire strippers
- Scissors
- Basic hand tools for panel removal
- Multimeter (recommended)
Materials
- Electrical tape (isolant tape)
- Heat shrink tubing (recommended)
- Wire connectors (included with S-AFC)
- Apexi wiring diagram T4-B
⚠️ Critical Safety Information
- Disconnect battery before starting any work to prevent ECU damage
- Expert installation recommended - incorrect wiring can damage the ECU
- Test thoroughly before driving - listen for unusual sounds or smells
- Have Apexi wiring diagram T4-B available during installation
- Professional tuning required after installation
Step 1: ECU Access and Preparation
Disconnect the battery to avoid any short circuit damage to the ECU.
Access the ECU by removing the glove box on the passenger side next to the central console. Once removed, you'll see the ECU with three connectors:
- E5 Connector: 26 pins
- E6 Connector: 16 pins
- E7 Connector: 12 pins
Carefully disconnect all three connectors from the ECU. Reference the Apexi wiring manual diagram T4-B throughout the installation process.
Step 2: E5 Connector Wiring (26-Pin)
RPM Signal Wire
- Location: 11th position, upper row
- Wire Color: Black and Yellow
- Procedure: Strip 5mm of insulation, attach S-AFC GREEN wire to exposed ECU wire
- Finish: Cover connection point with electrical tape
Ground Wire
- Location: 3rd position, lower row
- Wire Color: Brown
- Procedure: Strip 5mm insulation at two points (1cm apart)
- ECU Side: Connect S-AFC BROWN wire
- Non-ECU Side: Connect S-AFC BLACK wire
- Finish: Cover both connection points with electrical tape
Step 3: E6 Connector Wiring (16-Pin)
MAP Sensor Wire
- Location: 7th position, upper row
- Wire Color: Gray and Black
- Procedure: Cut wire completely, install provided connectors
- ECU Side: Male connector + S-AFC YELLOW wire
- Non-ECU Side: Female connector + S-AFC WHITE wire
TPS Sensor Wire
- Location: 7th position, lower row
- Wire Color: Black and White
- Procedure: Strip 5mm insulation, attach S-AFC GRAY wire
- Finish: Cover connection with electrical tape
Knock Sensor Wire
- Location: 3rd position, lower row
- Wire Color: White (slightly transparent)
- Procedure: Strip 5mm insulation, attach S-AFC PURPLE wire
- Finish: Cover connection with electrical tape
Step 4: E7 Connector Wiring (12-Pin)
Ignition Power (IG Power)
- Location: Last position, lower row
- Wire Color: Black and Yellow
- Procedure: Strip 5mm insulation, attach S-AFC RED wire
- Finish: Cover connection with electrical tape
Step 5: Initial Testing
With all connections complete, reconnect the battery and turn the ignition to the "ON" position. The S-AFC display should illuminate, indicating successful installation.
Step 6: Programming and Tuning
If everything is working correctly, the S-AFC II requires proper programming and tuning:
- Set base parameters according to engine specifications
- Perform careful air/fuel ratio adjustments
- Monitor engine performance during tuning
- Consider professional dyno tuning for optimal results
🔌 S-AFC Wire Color Reference
Input Signals
- GREEN: RPM Signal
- YELLOW: MAP Sensor (ECU side)
- WHITE: MAP Sensor (engine side)
- GRAY: TPS Signal
Power & Ground
- RED: Ignition Power
- BROWN: Ground (ECU side)
- BLACK: Ground (chassis side)
- PURPLE: Knock Sensor
Installation Photos
💡 Final Notes
- Keep the Apexi wiring diagram accessible for future reference
- Consider taking photos of your wiring for documentation
- S-AFC requires proper tuning to avoid lean/rich conditions
- Monitor air/fuel ratios carefully during initial driving
- Author (edo17982) available for questions via PM or email