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above : APEXi Super AFC on our Project GTi.
According to APEXi the SAFC is a "Piggyback Fuel Computer" that modifies air-flow meter signal to optimize the air/fuel ratio. It features an impressive Vacuum Fluorescent Display (VFD). On a naturally aspirated GTi you can increase the fueling and advance the timing (wih a timing light). This will net you good gains in both hp and torque and should be done on a dyno.
The SAFC is also very useful on turbo applications, it will let you use a blow off valve vented to the atmosphere.
Installing the Apexi SAFC - Installation is fairly easy if you have some experience with auto electronics / wiring.
Again in APEXi's words, it features a user-definable, eight-point, adjustable fuel curve that can be set in 500 RPM increments. The range of fuel adjustment is +/- 50% at each of the user-defined setting points. On hot-wire vehicles (like the GTi), the Deceleration Air Flow Correction function is capable of curing the erratic idle and stall problems associated with open-atmosphere blow-off valves. The S-AFC is also capable of monitoring and replaying the following data channels in Numerical, Analog Meter and Graph displays: Intake Manifold Vacuum/Boost Pressure, Air Flow Capacity, Intake Manifold Pressure, Karmann Frequency, Engine RPM, Throttle Position, and Air Flow Correction %. Finally you can also monitor the air/fuel ratio (this feature is undocumented).
Steps to install it
1. Remove your GTi seat (you'll need space to lay down to remove the ecm & do the wiring).
2. Unplug the harness's going to the junction fuse box (located near steering column). Then undo 2 nuts and it should be out of the way.
3. Next remove the 3 connectors going to the ECM ( A, B & C )
4. Above is a diagram that shows you where each wire is on the harness. Now you are ready to splice in the apexi harness with the ecm harness. You can either solder the wires into the stock harness or use quick taps.
5. Here are the various wires you will need to connect on your GTi.
a. Red Wire (Power) to A1
b. Green Wire (RPM Signal) to C6
c. Gray Wire (Throttle Signal) to A9
d. Yellow Wire (AFM output, close to ecm) to A6
e. White Wire (AFM input farther from ecm) to A6
f. Brown Wire (ground) to B6 (should be wired close to the ECM)
g. Black Wire (ground) to B6 on the manifold. See picture below.
h. Blue Wire (Air/Fuel) to A8. This is optional
Basic Setup Parameters
Once you have the unit up and running you will have to input some info.
1. Sensor Type - use HotWire w/ In and out set to 08. Sensor cal 1 and 1.
2. Car Select - Pick 4 cylinder and make sure the throttle arrow is pointing up
3. Grph Scale - Leave PR at 760mmHg on NA cars (higher on turbo cars). NE: 7000rpm (more if you rev often higher than that).
4. Sensor Check - Make sure you see some voltage on the afm and tps.
Now you are ready to tune the unit by modifying the high and low throttle fuel curves. The TH-Point is where you will define the difference between the low and high throttle. Setting the fuel curve is a simple matter of selecting the rpm point at which you want the correction made, and then using the arrow keys to indicate how much fuel you want to add or subtract. Between rpm setting the AFC will extrapolate the curve.
Since each GTi is different we can't make specific recommendations here and would suggest you get the car on the dyno and experiment on what works best with your modications. Please note this is a serious device and should be tuned carefully or engine damage can result. SSGTi.com takes takes no responsibility for damage or loss as a result of someone attempting to install this device.
Here are some sample screen shots
[ECM Codes]-[1.3->1.6 Swap]-[Turbocharging]-[Handling]-[Brakes]-[Wheels]-[Ignition]-[APEXi SAFC]-[Sohc->Dohc]-[Headers]-[Pulley]