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DPFI to MPFI Conversion (88-91 Civic)

Old 01-04-2006, 11:05 AM
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Join Date: Oct 2004
Posts: 4,358
Default DPFI to MPFI Conversion (88-91 Civic)

4G DPFI to MPFI Conversion
NOTE: These instructions assume you are prepping for a DOHC ZC swap, but they can be adapted to any other MPFI swap (SI, B16A, etc.). Other obvious parts that need replacing (i.e. intake manifold, dizzy, fuel lines, etc. are not dealt with).

- Injector Resistor Box (88-91 Si is generally favored, but any Honda/Acura box will work).
- 4 injector plugs
- Injector resistor box plug
- Distributor plug
- Extra wire

- Electrical tape or heat shrink tubing
- Wire stripper/cutter
- Soldering gun and solder (not necessary but highly recommended)
- Some motherf**king patience!

There are two major wiring changes that must be made when going from a DPFI to an MPFI system, as well as a couple minor things. The first one is the crank angle sensor wiring which is the easy part. The second one is the fuel injector wiring which is slightly more complicated. Also, you'll have to switch the two wires on the TPS because the TPS on the new intake works in the opposite direction. If you dont switch them, the ECU will think that the engine is at WOT when it's really at idle. Also, the TPS and EACV plugs are too short and will have to be extended.

Use this link (Microsoft Excel Required) to reference the pins used in this write-up:

1) Pins B10 and B12 on the ECU should both be empty.
2) Cut the wire from pin C1 (orange wire) and move it to pin B10, and move the wire from pin C2 (white) over to pin B12. Don't get these two mixed up or the ignition timing will be severly retarded. IMPORTANT: Be sure to leave enough wire on the ECU side of pin C1 and C2 for next step.
3) Now run wires from pins C1 and C2 into the engine compartment and label them.
4) There will be a connector on the MPFI distributor with two unused pins. One of the wires will be blue/green stripe, and the other will be blue/yellow stripe.
5) The wire that is blue/green stripe will go to the wire from pin C1 on the ECU and the wire that is blue/yellow stripe will go to the wire from pin C2.

INJECTOR WIRING (Inside the car):
Cut wires A3(yellow) and A7(red), leaving as much wire as possible for later use. Now extend the wires from pins A3 and A7 into the engine compartment and label them.

(Engine Compartment):
1) Mount the injector resistor box up on the drivers side strut tower.
2) Find the two yellow/black wires from the two DPFI injector harnesses, splice them together, and run it to the yellow/black wire on the injector resistor box.
3) Connect the yellow wire from the DX injector to the #1 injector wire (brown) on the injector resistor box.
4) Connect the red wire from the DX injector to the #3 injector wire (blue).
5) Connect the wire you ran from pin A3 to the #2 injector wire (red).
6) Connect the wire run from pin A7 to the #4 injector wire(yellow).
7) Finally, connect one of the 4 red/black wires from injector resistor box to each of the four injectors.

You should have three plugs left over after you are finished: two DPFI injector plugs, and one for the tandem valve from the DPFI system, which is unnecessary. You can either cut it off or tuck it away somewhere.

Pretty self-explanatory: just switch the two outside wires(green/white and yellow/white) around at the TPS.
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