How to: Field SFC VTEC Controller
The Field SFC VTEC controller has functions for altering the amount of fuel delivered to the engine in 1000 RPM increments, up to +/- 30% of the original amount. It also has a programmable shift 'beep' and speed limiter remover in addition to being able to alter the cam switchover point in VTEC's and MIVEC's.
For a fully translated instruction manual, click here
First of all, you have to find your ECU, this controls what goes on in your car and the SFC taps into it and in some cases modifies the signal from your ECU. In an Xsi, the ECU is under the passengers feet, just pull up the carpet and you'll see a metal panel with four 10mm bolts you need to remove. Now is a good time to take your negative terminal off your battery. Once this is off, you can lift your ECU out and unclip the wiring harnesses.
Strip the insulation back to expose the wiring and familiarize yourself with which harness is which, you will be tapping into 2 wires and cutting 4. You will need to solder 9 joins.
Your ECU looks like the pic below, the wiring will be covered by insulation tape, just cut it back and there will be a big mess of wires.
Pay no attention to the big yellow wires in the picture, they're for my speakers.
The red LED light in the middle tells you if there are any error codes showing up at your ecu, to find out what the codes mean, check out my ECU CODE PAGE
Use the picture above as a guide, if anything is wrong with my directions go with the picture because it comes straight from the instruction manual. Remember, this ECU may not match your car so if it isn't a 1990 Xsi, check out the instruction manual for the right picture. Full diagram
1) First, find the IGNITION POWER wire which is YELLOW/ BLACK, you will need to expose a 5-10mm portion of this wire to solder the RED wire from your SFC to. Do not cut this wire!.
2) Now find the RPM SIGNAL wire which is WHITE, once again, do not cut this wire, you need to tap into it by exposing the wire and making a solder join to the GREEN wire which comes from the SFC unit.
3) The first wire you need to cut is the VTEC SIGNAL wire which is GREEN/White. Make sure you leave enough wire on each side to join to. Make the cut and solder the end coming from the ecu to the YELLOW wire from the SFC, connect the other side of the GREEN/WHITE wire to the DARK BLUE wire from the SFC.
4) Find and cut the VTM wire which is colored BLUE/BLACK. Solder this to the GREEN/WHITE wire from your SFC. the other end of the VTM wire is not needed and must be insulated with tape.
5) Now find the SPEED SENSOR wire which is colored YELLOW/RED. Connect the end coming from the ECU to the PURPLE wire on the SFC and the remaining end to the LIGHT BLUE wire from the SFC.
6) Finally, cut the SENSOR LINE wire which is WHITE and solder the ORANGE wire from the SFC to the ECU end of the WHITE wire and the remaining end to the BROWN wire coming from your SFC unit.
Now that all the wiring is finished, you need to ground the unit and and reinstall the ECU. I found a bolt behind and to the left of the ECU to ground it to, it was the grounding point for another wire as well.
Replace the ECU and the metal panel, securing them with the 4 bolts.
You will need to find a place to mount the SFC unit, it can go pretty much anywhere, some people put it under their head unit or mount it on their steering column. Just make sure the wiring loom will reach your mounting spot BEFORE you do anything drastic.
I was considering a few places, in the end I decided to remove the heater vent under the steering column, and put it there. It fits perfectly, it looks like it was there from the factory.
With it mounted here, you can't actually see it while you're driving, your view is obscured by the steering wheel, it may be visible through an aftermarket wheel.
I'm not too worried if I can see it or not, because it can't be seen easily from outside the car by potential thieves. I'm sure once the novelty wears off, I'll forget it's there. The shift beep is easily heard from here as well.
Troubleshooting and making wiring loom
You might run into problems with the SFC like I did. My engine started to stutter and I had error codes appearing on my ECU. The code I got was the map sensor code and this is what was causing the stuttering. The MAP (Manifold Absolute Pressure) sensor measures the vacuum in the intake manifold to determine the amount of air going to the engine, some cars have an air flow meter instead.
The trouble with mine was the wiring plug which plugs into the back of the unit, some of the wires had come loose from the white plastic part of the plug and didn't make proper contact with the pins at the back of the SFC. I came to the conclusion that the wiring plug was crap and I would have constant problems with it until it was fixed.
I decided to get rid of the plug altogether, you can also follow these instructions if you don't have a wiring loom. I'm not an electrician but my SFC now works perfectly, I take no responsibility if you try this and ruin your SFC.
If you're handy with a soldering iron you can solder the wires straight onto the pins at the back of the unit. If you open the SFC up you can see a white piece of plastic which gets in the road of the pins, you can cut this bit out or melt it off with the iron, this will make your soldering easier.
If you look at the back of the unit you will see 16 pins set out like the diagram above. The 16 numbers correspond to the following colors, this is the way the wires were set out in the original plug.
11) LIGHT BLUE
With these wires soldered properly, you can install the unit normally.
This website has been gradually growing since I started it in early 2002. Originally I was simply documenting modifications and repairs to my car but I decided to publish it when I began to discover others were interested in the information. If you need help or have a how-to relating to Honda B series VTEC engines, or DA or DC2R Integras you can
While all care is taken to provide correct information, mistakes are occasionally made and I cannot be responsible for any damage that occurs to readers vehicles.