Step 5: Under construction

Mounting the computer, running wires, and tuning

The computer is water resistant and splash proof but not water proof. The actual box is sealed and the circuit board is coated so it's not easy to get wet but if it's submerged there is a chance that water could get through the potentiometers The following shows my temporary mount. It's high enough for any water crossings I plan to do in the near future. Later I will mount it on the dash and probably put a water proof radio cover on it like some boats use. The actual position of my box is a bit awkward to use with belts on and it turned out to be a real PITA when I was playing with the knobs to see how everything worked.

This is the wiring harness that Tim Systems sells. The wires are all color codes and the connectors are attached. (It's well worth the money unless you have all the wire on hand already)

Notice the two twisted wire sets. One goes to the TPS and the other goes to the map sensor. The twist is there to cancel out any electro magnetic interference (EMI) that would confuse the computer.

Tim supplies a wiring diagram with the computer. For the wiring impaired, don't let the number of wires confuse you. It's pretty easy if you just run one wire at a time.

Starter and Ignition wires:

When the computer sees you hit the starter it turns on the fuel pump and the injectors. I chose to run this wire directly to the starter solenoid. The reasoning is that sometimes I have had to disconnect the starter wire and use a screw driver to start the engine. By running the start sensing wire directly to the starter I can disconnect the started switch wire and the computer will still operate. (Remember this is going on an offroad buggy and bad switch connection are not uncommon)

I ran the ignition wire directly to the coil resistor for the same reasons. Notice I said coil resistor, not the coil. The input of the resistor is 12 volts, after the resistor you only have about 6 volts going to the coil. If you don't need a resistor on your coil then I would just run it to the coil positive. Also make sure that your primary ignition wire is large enough to handle the extra current of the computer.

((Insert coil picture here))

After the wiring is done it's time to double check all the wires. On my installation I forgot to bolt the ground lug onto a ground after I soldered the lug on. I also wired the fuel pump relay backwards...double check your wiring carefully before hitting the key!

When you turn the ignition on you should hear the pump prime for a brief second. At this point it will wait for you to hit the starter before if turns on again.

TPS and Idle Adjustment:

The first thing to adjust is the TPS voltage. There's a test port on the box that is for telling you the voltage of the TPS and you'll need an accurate digital voltmeter to dial it in. Set the meter to a scale under 20 volts and turn off any auto-ranging option. Turn the TPS knob on the computer counter clockwise and the TOP knob clockwise. Set all the others in the center. Plug the positive lead of the multimeter into the test port and ground the negative on the box. Turn the ignition on but don't start the engine and check the voltage. Adjust the TPS sensor on the throttle body until the voltage reads about .70 or .75 volts. Now floor the accel pedal and make sure that the voltage is repeatable and that it drops back down to the same range. Slowly open the throttle and make sure that the voltage increases smoothly. If there's any stutters or jumps in the volt reading then get a new TPS. The voltage should increase to between 4.3 and 4.5 volts at full throttle. Because of play in my used throttle valve I had to grind my throttle stop to get max voltage.

((Insert picture here))

Turn the TPS knob so that the voltage is reading .8 volts. Now the engine should start up and idle. For future adjustment purposes you want to tune the computer so the idle knob is centered. That provides leeway both ways for when the weather changes.

What you need to do is slowly turn the TPS knob to find the voltage that the engine likes running at with the idle knob centered. At this point it's important to keep in mind that the throttle body is what is controlling the air flow necessary to idle and the computer is just supplying the proper amount of idle fuel. You need to match the fuel to the air flow. If the engine does not idle at the proper speed when the TPS knob is adjusted for fastest idle then adjust the airflow by turning the screw on the throttle body. You will also notice that as the engine warms up it will idle faster. This is because when the engine is hot it is more efficient. I played with the knobs while the engine was warming up and then did the final adjustment when it was at operating temperature.

So basically you need to go back and forth between the throttle valve adjustment to get the air flow right and the TPS adjustment to get the fuel right. Make small changes and you will find the spot where there is the proper amount of idle air, the proper amount of fuel, and the idle knob will cause a drop in RPMs when you turn it both ways.

At that point make note of the voltage. You want the TPS knob to have a minimal effect on the TPS sensor voltage. Turn the TPS knob all the way counter clockwise and then adjust the TPS sensor to just below the target idle voltage you want. Then use the TPS knob to bump it up to the proper voltage.

Setting the mid range is easy. Drive at 2000 RPMs and turn the MID knob until the engine runs right. The MID knob controls the fuel when you are just off idle in the 1500-2500 RPM range.

The TOP knob comes into play over 2500 RPMs. Start with the TOP knob all the way up and accelerate. By turning the TOP knob you should be able to feel when the engine bogs down and loads up. Adjust it for the best power. When you got it right take a look at it's position. To keep the injectors at a high duty cycle you want the top knob to be almost all the way clockwise when everything is tuned properly. To do that you will have to change the fuel pressure. For example say the engine runs best when the TOP knob is centered in it's travel. That means that the computer will be driving the injectors at a slower than optimal duty cycle. If you lower the fuel pressure, less fuel will flow into the engine at the same computer settings and you can increase the duty cycle on the injector by turning the TOP knob higher. If your wondering if that's going to screw up your other adjustments, the answer is YES. You will have to re-adjust the TPS slightly, readjust the MID, and do another high speed run. Don't worry, it's a whole lot easier to do than it is to explain.

Accel Knob:

This knob is only necessary on some setups depending on the engine and injector location. It controls fuel enrichment based on RPM and the rate of change of the throttle. Start with it turned off and adjust it until you have the best throttle response.

When you get the computer dialed in, take a jeweler's screw driver and loosen each knob and point them in the same direction. I went one step further and put O-rings under each one so that the knobs are harder to turn.

Driveability:

The best way I can explain it is that it's not the same car any more. Throttle response is right on and the float problems are a thing of the past. It was easy for me to see the difference between the Kadrons and EFI but perhaps my girlfriends experience will explain it better.

Last night I gave Courtney her second "driving lesson". The first "lesson" was with Kadrons at night in the mountains and we had to climb a fairly steep grade that was rutted with huge dozer tracks and littered with boulders. The bumps and slow speeds were flooding the engine and I had to tell her to keep it floored even though we were pretty much only on 2 wheels at any one given time. She also had to dump the clutch a few times to clear out the plugs. It was almost a nightmare ;-)

The second "lesson" was in pouring down rain with the new EFI. After a few laps around the track I asked her if the buggy felt different. With this big grin on her face she says "it drives much better now...I like it...it just wants to go...can I go around again." A few laps later the rain was coming down even harder, we're driving on top of a couple inches of water at 25mph with the spray going everywhere and frankly I don't know how she could see. (It may be a problem getting her out of the car in the future) Her third driving lesson will be steering brakes...rain or shine.

The next thing to do is take some dyno runs to get a baseline before the turbo gets bolted on.

Stay Tuned.....

[ Step 1: Fuel Tank ] [ Step 2: Flanges and Plenum ] [ Step 3: Runners and Rails ] [ Step 4: Plumbing and Testing ] [ Step 5: Computer Wiring and Tuning ]