Piggyback Heaven – How to Install a SAFC in a BB6 Honda...

Piggyback Heaven – How to Install a SAFC in a BB6 Honda Prelude


The Apexi Super AFC is a piggyback tuning computer that basically changes the reference signal your ECU uses to operate the motor. The ability to adjust this signal allows you to tune and adjust the fuel delivery of your vehicle dependent on RPM and throttle response. Crude but effective, the Super AFC gets a bad rap from Internet forum “gurus” who just repeat what they’ve heard elsewhere.

When using a piggyback like a AFC.
We are installing 401-A911 part number

Used Super AFC’s are relatively cheap and plentiful, making this a good choice for turbo H22’s especially with our Honda Super AFC Hack. Today I’ll be showing you how to install a Super AFC in a 1998 Honda Prelude VTEC with a 2.2 liter H22A motor. The AFC we are installing is part number 401-A911, although 401-A913 applies as well. If you own a AFC NEO or different Super AFC, the instructions will not vary outside of additional power and ground wires.

The ECU we will be working on is the Honda VTEC P5M and I’ll walk you through the How to Install a SAFC in a BB6 Honda Prelude Guide.



In order to access your Honda Prelude ECU, open the passenger side door and pull back on the passenger seat of the car to the furthest position. Under the passenger side carpet there’s a metal plate that protects the ECU and harness. It’s secured by 4 10mm bolts, remove these and pull off the metal plate to access your P5M Honda Prelude VTEC ECU.


The Honda Prelude H22A engine operates on a Manifold Absolute Pressure system which feeds the P5M ECU. Because the engine runs on a MAP signal, you will be wiring in the yellow and white Apexi Super AFC wiring harness, instead of the pink and orange for Karman MAF engines.

Take the second half of your AFC flying loom and disconnect the negative terminal of your battery. Unplug the P5M ECU and reference the image below for the complete Honda Prelude ECU wiring harness. There are three main ECU plugs that must be unplugged for you to complete the wiring installation of your Apexi Super AFC.


First take the red wire from the AFC harness and you will be wiring this into the ECU plug labeled “A”. The pin you will be teeing is shown below and its A24, EFI relay switched power and is a black wire with yellow stripe. Now that you have the power hooked up, you will move onto the grounds, there’s two wires for this ground that must be wired in specifically to the A22 pin or the brown wire for ground.

Reference the image below to see how you are supposed to be wiring in the brown and black wires of your AFC for a ground signal. Never mix or put these wires in together, always wire it as you see below to prevent premature damage to your AFC.


Double check your wiring for the power and ground signals, making sure that you have a one inch gap between the brown wire and the black wire. Once you have both grounds wired, you are now ready to move onto the Apexi Super AFC sensor input section of our How to Install a SAFC in a BB6 Honda Prelude Article.

The next wire you will be teeing into your ECU harness is the green AFC wire, this wire is for the engine speed or RPM. This wire should be teed into the A20 wire which is a yellow wire with green stripe, this wire is otherwise known as the ICM wire for spark pickup.

Now it’s time for the throttle position sensor or the TPS sensor signal, this is teed from C1 the TPS Signal of your P5M Honda VTEC ECU. Wire the gray wire from your Super AFC into this wire by stripping back some of the insulation and soldering the wire inline of the harness.


It’s time for the first cut of the installation, and that’s to the MAP signal wire on the C plug of the Honda ECU. The pin C3 is the middle plug on the top row of the C connector, and it’s a red wire with green stripe. Cut this wire but leave enough slack on either end so that you can solder or crimp your butt connectors to each wire. The Manifold Absolute Pressure (MAP) signal from the engine should be leading to the WHITE AFC wire, and the ECU side of C3 should be wired to the yellow side of your AFC harness.

Complete the setup of your Super AFC by setting the ENGINE type to four cylinder with the arrow pointing upwards. Set the sensor type to pressure because your P5M ECU is MAP based, and the value for IN and OUT should be set to 6. If you need help on How to Setup your AFC, check our guide here.

You have now completed the basic tutorial on How to Install a SAFC in a BB6 Honda Prelude Guide. There are two additional steps that you can take however if you want a more custom installation of your Apexi Super AFC.

The purple wire is the knock wire of your AFC, and this wire can be connected to the Knock sensor signal (KNK) on the C plug. C6 is the wire that you will want to tee the knocking wire into, and this wire is red with a blue stripe on the Honda harness.

The blue wire of your AFC is the option wire, which can be referenced through the ETC portion of your AFC menu. You can wire this into the oxygen sensor wire, which is C7 for the H02S signal wire for your oxygen sensor.

Have any questions about this How to Install a SAFC in a BB6 Honda Prelude Article? Leave us a message or question below.