Piggyback Heaven – How To Install a JDM SAFC

Piggyback Heaven – How To Install a JDM SAFC


We will be installing a JDM version of the Apexi Super Air Fuel Controller in a 1998 Mitsubishi Eclipse GSX Turbo in this writeup. We will be covering the basics of install as well as covering ground on how to setup your AFC as well as how to tune part throttle and wide open throttle maps.

A look at the JDM version of the Apexi SAFC is below :


Outside of the Japanese instruction manual, everything about this AFCII is identical to the units you would find in the US.





The SAFC II is a basic tuning device that changes the inputs leading to the PCM or ECU to achieve the tuner’s desired air / fuel mixture depending on engine load, engine RPM as well as throttle position. While this is still a very crude way of tuning your vehicle, it’s more than capable of reaching the 450 whp number in our Mitsubishi GSX.

Before trying to install your Super AFC II, you will want the following tools ready :

  • 1 Phillips screwdriver
  • Wire Strippers
  • Solder Gun
  • 10mm ratchet
  • Electrical Tape
  • Spatula or Panel Popper

Here is a look at the wires that we will be teeing or splicing into your ECU harness today.

o o o o o o o o
Red Wire
Black Wire
2nd Ground
Brown Wire
1st Ground
Green Wire
Gray Wire
Purple Wire
Pink Wire
Air Fuel to ECU
Orange Wire
Air Fuel to Sensor

Here is a second generation Eclipse pinout with corresponding AFC wiring in vertical fashion, we will be taking a look at each block of wiring as we go along.

Initial AFC Setup

A few installation tips first. Be sure to use the Pink and Orange wires for the airflow signal wires, and NOT the Yellow and White wires. The AFC is a universal device and is setup to handle both Speed-Density and Mass-Airflow type systems. The Pink and Orange wires are for Mass-Airflow systems like DSMs.

In the Setting Menu, set the Th-Point to 69 for Lo and 70 for Hi. Set the Ne-Point so the RPM points are 1000, 2000, 3000, 4000, 4500, 5000, 6000, 7000 for stock rev limiter, or 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000 for raised rev limiter.

In the Etc Menu, set the Sensor Type to “Karman” for a DSM. The Car Select should be set to Cyl 4 with the Thr arrow pointing up meaning a rising rate throttle position sensor. Set the GRPH Scale to 30, Initialize will reset everything to factory defaults so it should be set to No.


As the image to the left indicates, do not use the 2 subharnesses as they have no wiring that is needed for this install, merely set them aside once you gain access to the ECU.

Speaking of which, let’s begin.

First, slide the driver seat as far back as possible to gain as much room as possible, and as always if you are unsure of any work you are doing, we recommend you take your vehicle to an experienced mechanic. Next take a look down at the driver side of the center console / leg panel and gently remove the plastic tabs covering the screws that hold this panel on.

Once you have gained access to the screws, use your phillips screwdriver to remove them. Now that your panel is loose follow your panel back until you reach the push in tab directly next to the driver seat. Gently pop this tab off and you are ready to take off the entire panel.

Now you have access to the ECU, take a moment to disconnect your battery before unplugging the ECU harnesses from the ECU. Take note that 2 of the sub harnesses will not need to be removed as referenced in the ECU pinout above.

Now unplug your ECU by gently depressing the tabs and pulling on the plastic harness part of the plug, DO NOT YANK on the wires.

First find the ground and black wires on your AFC harness, these are your primary and secondary ground wires that you will need to connect to the ECU ground pin.

Find the ground wire on pin 26 and use a wire stripper to peel away and expose a section of bare wire relatively closer to the ecu side than the harness side. Make sure to give yourself enough slack to make another strip slightly higher up in the harness later for your secondary ground wire.

Solder / tap your brown AFC wire to this section of black ground wire, and then strip away a section of insulation about an inch down the harness for your secondary ground wire.


Now take your black AFC II ground wire and tee / solder this into the section that you just stripped away. Remember, this section should be FURTHER away from the ECU than the brown wire and about an inch down the wire in length.

Be careful not to mix this up.

Now locate your red AFC II wire, this is your primary power wire and this version of the AFC II has just one wire for power. Your AFC may have 2 power wires, one red and the other red with a white stripe, if so please check your AFC NEO wiring diagram for the proper sequencing of your connection.

Or you can check out our AFC NEO installations in our How To Section for further details.

Now locate pin 25 on the same harness for the red AFCII power wire, you should now have power

Now locate your green AFCII RPM wire and find the ECU pin 58 for the RPM signal to your AFC II unit.

Then find the gray AFCII throttle wire and tee / solder that into pin 84 on your ECU which is a brown wire with red stripes.

Now comes the only wire you will have to cut in order to complete your install of your Apexi Super AFC II. Locate the AFM wire at pin 90 and cut this wire but leave yourself enough room to be able to solder / tee / repair. Connect the ecu side of the wire to your pink Super AFCII wire and the harness end of the wire to the orange Super AFC II wire.

You may or may not want to take this time to do the “blue wire mod” which is an external signal feed that you can tee into your 02 sensor giving you on-the-fly 02 readings from the “ETC” Menu on your AFC II.

On the wire harness for the AFC there are three wires that normally not used on an Eclipse. These are White, Yellow and Blue. The Blue wire is meant for the second Air Flow Meter on a Nissan 300ZX. You will connect this wire to the O2 sensor wire right at the ECU.

To utilize your “blue wire mod”, scroll down to and select the “etc.” menu. Select the “Sensor Check”. Of the three readings, O2 voltage will be the middle one (#2)

Now you have successfully installed your Apexi Super AFCII, make sure to wrap everything up and tape everything nicely to prevent any electrical gremlins from rearing their ugly heads.

Connect your ECU and reconnect your battery and you can start the setup of your Super AFC II. This version is the first unit with the thumbstick in the middle of an operational dial to navigate through its many menus.

If you depress this thumbstick at any time it will bring up a 4 way option screen CANCEL > Previous > Next > Menu. In most instances a tap left or right on the thumbstick will take you to the previous or next screen easily.

Bar display in the “MONITOR” mode and settings, you can select different fields to monitor, snapshot and freeze frame by pushing to the left on your stick during operation.

The same “MONITOR” setting only in data form and without the bar graphs.

If you haven’t already, now might be a good time to choose a password with which to lockdown your AFC. After all, you don’t want the wrong person to fiddle with your fuel trims do you?

Next up, how to tune your Apexi Super AFC II and don’t forget to check out the rest of our Piggyback Heaven section for more details on how to use your AFC II!

Happy Tuning!

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