Honda Mileage: VID installation

In the last post, I talked about VID calibration. Perhaps, what I should have talked about was how I installed the VID device in a pre-1996 automobile in the first place. Since I started with nothing but a voltmeter and oscilloscope, I may have had a slight advantage over someone simply trying to hook this thing up to some anonymous type of automobile. However, anyone that is capable of building this device (from the schematics) is more than capable of figuring out how to hook it up.

At any rate, I did not want to take any chances with the ECM wiring in this car. I therefore, stayed completely away from that part of the electrical system. Instead, I found the fuel injector ballast resistor block under the hood--this indicated to me that I had a saturated type injector system. In this case, the ballast resistor block is located on the driver's side of the engine--mounted near other electrical components near power steering reservoir. (I talked about the two types of fuel injectors in my past post.)

I nicked into one of the black wires connecting the ballast block with one of the fuel injectors. ( I think it was #1 cylinder--but it does not really matter.) I connected this with another wire of sufficient size and specification to ensure its wear resistance integrity as it passed through the fender wall and across the rubber door mounting, and into the passenger compartment. (I found no easy way to pass the wire through the firewall). The fact that this wire passes across metal door parts almost demands that a small fuse be installed in series near the tap in point--i.e. a short to ground here could affect the output transistor in the ECM.

As for the VSS: I am lucky to have a vehicle with a conveniently located cruise control box (CCB). In my case, the CCB is located under the dash directly below the steering wheel. I first removed the CCB from the connector. Then, while referring to the electrical schematic of the vehicle, I located the VSS wire. (In this case, this is a orange wire coming from the speed sensor.)

The next thing was to find a suitable source of power and ground for the VID. The CBB connector also provided a convenient place to make these connections as well. For me, this setup was ideal, because I wanted to be able to control the power to the VID by the same switch that controls power to the cruise control. So I tapped into three wires near the CBB connector with a type of connector that allowed me slip the connector over the target wire, and close them with a pair of pliers. Doing this, laces the target wire, creating a reliable, but 'semi-easily removable attachment point for the wire attached to the other half of the connector. I then installed three 18 guage wires into the three CCB attachment point connectors. The three wires from the CBB jointed the wire coming from the fuel injector connection under the hood. I then brought all four wires out from below the dash and into to a 9 pin molex style power connector. I finished connecting the wires to the VID by using the mate to the 9 pin molex connector. When I was finished, I could remove the VID from the vehicle by detaching one end of the molex connector. Since for development purposes, I used a vehicle simulator, this connector arrangement made it convenient to attach the VID to either system.

At any rate, this is what I did. What someone else would do depends on his/her particular vehicle. Obviously, the vehicle must be fuel injected. And, if the fuel injector system turns out to be a saturated type, this device design would most likely work--as is.

NOTE: Most ECMs will have connection points for both the VSS input and the fuel injector outputs. However, it might be better to NOT disturb the ECM, if that can be avoided.
In all cases, I would recommend that 1/4 amp inline fuses be installed in series with both signal lines (VSS & INJ) The VBATT line could also be fused. However, in most cases, as long as the power source is already fused, this may be unnecessary. In my case, the fuse that controls the cruise control box also protects for the VID.