Apex'i S-AFC Installation on Toyota Celica

This write-up describes how to install an Apexi S-AFC (Gen1) on a 94-95 Toyota Celica (5S-FE). It may work with other generations, but you’ll have to figure out the wiring yourself.

Basically what the S-AFC does is alter the voltage the ECU receives from the MAP sensor. This causes the air/fuel mixture to either go leaner (-) or richer (+).You can adjust in increments of 2%.You can fine-tune the mixture at different RPM points (800rpm, 2400rpm, 4000rpm, 5600rpm, 7200rpm).Obviously the last setting is not used. The ECU won't use the values of the AFC while in closed loop mode (under 80% throttle). But when you step on it (when racing), the ECU goes into open loop mode, ignoring the O2 sensor and only relying on the MAP sensor for data. So the Gen1 AFC is only usable under WOT (Wide open throttle) situations. I don’t promise huge hp gains, but with Intake/Header/Exhaust and correct tuning, you’ll get a few more horses!

Tools Needed:

• Apexi S-AFC and harness
• Wire taps/connectors
• Wire stripper/cutter
• Multi-meter
• 10mm socket
• ECU Diagram
• 3-4 hours of patience!

You can also download the actual manual from the Apexi website:
http://www.apexi-usa.com/productdocunt ation/electronics_afc_gen1.pdf

Step 1:Disconnect the battery

This step is a no brainer. You’ll be playing with the ECU so you definitely have to disconnect the negative. Loosen the 10mm bolt from the battery and wiggle it off. Wait 90 seconds then continue to step 2.

Step 2: Setup the AFC

Since the 5S-FE uses a MAP sensor, we must set it up to use it. So, on the back of the AFC, set the CAR SELECT to 3 and TYPE SELECT to

NOTE: For those installing Gen2 AFC’s, the correct sensor should be PR-3

Step 3: Find a place to mount it

I decided to mount the AFC under my CD player.That’s because there was a hole there anyways, since I had the double DIN Tape/CD combo before. I just found some nice plastic and cut away! You can also put it in your glove compartment, but then, how can you see it??

Step 4: Locate the ECU

For the 6th Gen Celica’s, the ECU is easily accessible.All I did was pull at the carpet and there it was.Here is the picture of the ECU pin-outs.

Wire Color	ECU	What is it?
Red Wire	IG Power	12v power source
Black Wire	Ground	Grounded source
Green Wire	RPM Signal 2 (20A)	Signal from Igniter
Yellow Wire	Pressure Signal (2B)	Signal from AFC to ECU
White Wire	N/A	Signal from MAP sensor to AFC

Step 5: Tap the wires

Using the above diagram, tap the red, black, green wires first. Since those don’t require any cutting.The Map sensor wire requires cutting. There wasn’t much room to work with so I just cut the MAP sensor wire half way.Attach the yellow wire from the AFC into the wire to the ECU. Connect the white wire to the other end. NOTE: DO NOT MIX UP THE WIRES FOR THE MAP SENSOR! I did the 1st time, got a check engine light, and the car died.

Here is a picture of the installation, I will tidy it up later, but it is winter now, and its too cold outside!

Step 6: Clean up
Check that all your connections are tight, and put everything back to where it was. Also, make sure that all your settings are 0% 0% 0% 0% 0%. After everything is done, reconnect the negative battery (and don’t forget to set your clock!!)

Step 7: Go for a drive
Start the car. It should idle a little high (1000rpm), but once the engine warms up, it’ll be back to normal (750-800 rpm for me). There should be NO check engine light!If there is, shut the car off immediately and check your connections!!!! Do not try to adjust the settings of the AFC, WITHOUT a DYNO! I’m not responsible for you leaning the engine out and blowing up your block! Although running extremely lean will make more power, it will also make your wallet unhappy from the engine swap.

Step 8: Setting up a AIR/FUEL gauge (Optional)
For those of you who also want to install an a/f gauge, you can tap into the ECU wire 5B or 6B. It’s the pink wire from the O2 sensor.

Step 9: You’re done!
It took me around 4 hours to install the AFC. But I had help from my brother. So it may take you longer! If you have no previous electrical experience, then I would not recommend you do this mod, but you are always welcome to try! Here is the picture of the AFC at night. The knobs light up green, and the rpm you are at light up as red. When you rev the engine, it gradually fades to the next knob. Very cool to watch at night!!!ENJOY!