I got into the turbo Regal wiring in general as a result of watching my voltage drop in the course of a quarter mile run on a data log. I was alarmed to see the voltage drop to the high 11s or low 12s. Why I was so concerned was a feature in the FAST XFI that is not programmable shown in the illustration below taken from the FAST installation/programming manual:
In short the FAST system adds a percentage to the injector pulse when it senses a lower voltage. Running E-85 in that particular car with larger injectors, a small percentage here is a big deal. That lead me to figure out where my losses were.
To measure the drop in the OEM 8 gage wire, between the alternator and battery, I measured the voltage across this 6 ft. length of wire. With the normal idling load and electric fan running (I have the resistor bypassed so it it either on or off), I measured 2 tenths of a volt between the battery post and the alternator post. Measuring the voltage at each point corresponded to the loss. There was 14.7 volts at the alternator post and 14.5 volts at the battery. This amount of resistance was a little high according to the calculator at the bottom of the link:
American Wire Gauge table and AWG Electrical Current Load Limits with skin depth frequencies. Even after cleaning and tinning the terminals I saw 1 tenth of a volt.
While reading this voltage at the battery the FAST XFI dashboard was reading in the low 13s. About this time in a thread on this board, I discovered that flash version 5.6 of the XFI read the input voltage to the computer 6 tenths of a volt low. Cal Hartline came to the rescue with beta flash 5.7 that corrected that problem.
With the flash installed the voltage read almost an even volt below the battery voltage. I gained almost a tenth by changing the 8 gage wire to 6 gage reducing the voltage drop across that wire taking my battery voltage closer to the alternator output voltage. Small increment to some, but important to the total goal I was trying for. (This is not the car that I already upgraded this wire and alternator to help in the idling voltage at night in the rain on the way home from a cruise night with the AC on)
Then I decided to hot wire terminal F of the 437 connector (located under the glove box, near the ECM). I had earlier installed Caspers fusible link relocation kit, so from the terminal block added a 10 gage wire (I plan to add other things so maybe over sized) to a relay behind the glove box. Used the original wire to terminal F from the ignition switch to trigger the relay and the output of the relay to now supply power to the computer and as a bonus the CCCI module through terminal F of connector 437.
The results were the voltage at the computer now read very close to the voltage output at the alternator, reducing the variation imposed by FAST to the injector pulse width for a perceived low voltage. The next step is to use a second relay I installed to supply the fuel injector harness directly, which may help a little as I'm using low impedance injectors.
You can expect a little voltage loss per connector, so figuring all the connectors, ignition switch, fuses, fusible links etc in the circuit no wonder anybody monitoring the voltage at the ECM is seeing a low voltage. All the little steps add up.
Just a few more things to add to the wish list when I have John Spina make up my custom wiring harness for this car.
