Apexi S-AFC Installation Guide

Nissan 240SX Information – Apexi S-AFC Installation Guide

This page provides detailed instructions for installing a Apex’i S-AFC in a 1991-1994 Nissan

Apex’i Super Air Fuel Controller: The Apex SAFC allows you to control
how much fuel will be delivered at certain rpms. This unit is mainly used
for people who have changed either there MAF, injectors or cams. For best
results this should be tuned using a dyno to insure proper settings. It provides many display
modes such as RPM and Throttle % as well as having three brightness settings
for optimal viewing.

  • Electrical Tape
  • 10mm Socket
  • Phillips Screwdriver
  • Wire Striper
  • Tap Connectors (Optional)


  • Disconnect Negative Battery Terminal

Remove 3 Screws on Passenger Side Kick Panel

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Remove Clear Cover That Snaps on Over The ECU Main Wiring Harness

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Remove The ECU Wiring Harness From The ECU by Using The 10mm Socket

I used a tap to connect my wires to my ECU, the tap allowed me to install
my afc without cutting any wires on the main harness for the ECU(see picture
of tap below).

Installation Instructions:

  • Proper Wire Range (19-26 Gauge)
  • Without cutting conductor, place unstriped run-wire inside run channel.
  • Be sure tap wire is evenly cut. Push lightly on wire until it is as far inside the opening as possible.
  • Use pliers to press down on connector cap until flush with the body if the connector.

NOTE: Wires should not be twisted after the connectors have been installed.

240SX S-AFC Installation Pictures

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Click For a Larger Picture

Apex’i SAFC Wiring Harness Function KA24DE & S13 SR20DET ECU Wiring Harness
Red Power Black with White Stripe
Brown Ground Black
Black Ground Black
Green Engine Tachometer (RPM) Yellow with Red Stripe
Gray Throttle Signal White
Yellow Air Flow / Pressure Output White
White Air Flow / Pressure Input White
Blue Not Used Not Used
Pink Not Used Not Used
Orange Not Used Not Used

During Installation ECU Picture:

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Completed ECU Picture:

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Monitoring Choices:

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Analog View of RPM and Throttle:

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Analog View of RPM and Throttle with Graphic Equalizer:

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  • joe

    so i followed your wiring which was excellent can you please help me to setup the unit it’s self i do not want to program it wrong.

    1993 nissan 240sx
    hks ssqv
    370cc injectors
    enthalpy ecu
    wide band
    apexi safc II
    walbro 255
    z32 maf

  • Q-Garage

    I cannot belief till this day and age that there are someone who is willing to use a SAFC for purpose other than read out.

    1: You cannot use 370cc injectors with a Z32 MAF. It doesn’t work. The minimum injector size for the Z32 MAF setup to function correctly is 550cc or above.

    2: Seeing that you already have a tuned ECU, you should not use a SAFC to make any kind of adjustment. Use the SAFC for read out functionality. You should not pass the MAF wire input into the SAFC but rather just tap it for read out.

    If you need further adjustment, you should go back to Enthalpy and have him change the tune rather than you trying to hack up the author’s work by moving around the load point with SAFC.

  • Josh

    I got all the stuff for the turbo setting. I Got Walbro 385, 550cc Injector, 12:1 Gas regulator, Turbo T28…. Is my first time and i want to know what kind o work I need to do to my Stock Ecu.., that’s the only things that is stopping my to install the Turbo and buy the Apexi Safc. If you can help, i’ll apreciate it…

  • ze

    Just brought a second hand apexi safc. I wired the power and negatives to test the apexi. The orange light the buttons comes on but the screen is not coming on. Do I need all the wires wiredin to test the unit

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