mrobertweiss
04-28-2011, 11:05 AM
I have a mass flo EFI system I set up on a studebaker 289, with a twin turbo. I posted a picture elsewhere on this forum. Tech support can be a bit of a joke with MassFlo, (another story) and I want to use their wiring harness to better control my high current-draw fan. I was wondering if anyone has considered this issue:
There is an AC wiring hookup in their harness,( which is basically an A9L 1992 Mustang EEC IV, and mustang harness), that achieves 2 things: it commands idle to increase when the AC clutch is engaged, and it shuts off the AC compressor at WOT. One wire from terminal 54 of the EEC is a ground for a relay to shut off the clutch at WOT, and is to be attached to the AC compressor wire, the other wire in the harness goes from terminal 10 of the EEC , a continuous 12V feed, and is supposed to attach to the AC control switch. In other words, the two wires from the EEC IV go inline with the normal AC control wire, to the compressor.
I don't have AC on this system, but I do have a HO Spal fan that draws 28-30 amps, with a big inrush current, much more than your avg compressor. It's enough to pull the voltage down from 14-14.5 volts at idle (about 980-100 rpm is what is best for my engine), to maybe 13 volts, especially if the headlights are on. I have a supposed max 220-amp, one-wire alternator from "Powerbastrds" (and whether it really can do what they say is another story), but the alternator seems to be doing otherwise rather well, and I have no voltage drops in the system otherwise. All new wiring. There are big 1-0 and 2-0 marine wires for everything(1-0 for the trunk mounted battery feeds, 2-0 for the starter, etc). The MassFlo EFI harness has a relay box, that contains a 12 Volt fan relay output, that activates at an ECT of 205 degrees, which then sends 12 volts to my Tyco/Spal heavy-duty relay signal/trigger terminal,that runs the fan. It works fine, but I wanted to run that first relay output back thru the EEC(using the AC wires provided), such that I will get a little additional idle RPMs, when things are hot outside, and assure 14+ volts to the fan. There's a noticeable reduction in fan RPMs from 14+ volts, to 13 volts . The fan gets its 12 volt power input from the Tyco HO relay, which is right next to the alternator output terminal, so there is no current or voltage drop there.
It seems to me that the computer and harness don't know what they are running, and putting my electric fan on the control would be viewed as essentially an AC compressor by the harness/relay system. Shutting off the fan, were it on, at WOT would be incidental. Does this sound ill-advised, or like I haven't thought it thru correctly?- I think it would help my fan run stronger and safer at idle, and provide solid cooling at idle. thanks, m weiss
There is an AC wiring hookup in their harness,( which is basically an A9L 1992 Mustang EEC IV, and mustang harness), that achieves 2 things: it commands idle to increase when the AC clutch is engaged, and it shuts off the AC compressor at WOT. One wire from terminal 54 of the EEC is a ground for a relay to shut off the clutch at WOT, and is to be attached to the AC compressor wire, the other wire in the harness goes from terminal 10 of the EEC , a continuous 12V feed, and is supposed to attach to the AC control switch. In other words, the two wires from the EEC IV go inline with the normal AC control wire, to the compressor.
I don't have AC on this system, but I do have a HO Spal fan that draws 28-30 amps, with a big inrush current, much more than your avg compressor. It's enough to pull the voltage down from 14-14.5 volts at idle (about 980-100 rpm is what is best for my engine), to maybe 13 volts, especially if the headlights are on. I have a supposed max 220-amp, one-wire alternator from "Powerbastrds" (and whether it really can do what they say is another story), but the alternator seems to be doing otherwise rather well, and I have no voltage drops in the system otherwise. All new wiring. There are big 1-0 and 2-0 marine wires for everything(1-0 for the trunk mounted battery feeds, 2-0 for the starter, etc). The MassFlo EFI harness has a relay box, that contains a 12 Volt fan relay output, that activates at an ECT of 205 degrees, which then sends 12 volts to my Tyco/Spal heavy-duty relay signal/trigger terminal,that runs the fan. It works fine, but I wanted to run that first relay output back thru the EEC(using the AC wires provided), such that I will get a little additional idle RPMs, when things are hot outside, and assure 14+ volts to the fan. There's a noticeable reduction in fan RPMs from 14+ volts, to 13 volts . The fan gets its 12 volt power input from the Tyco HO relay, which is right next to the alternator output terminal, so there is no current or voltage drop there.
It seems to me that the computer and harness don't know what they are running, and putting my electric fan on the control would be viewed as essentially an AC compressor by the harness/relay system. Shutting off the fan, were it on, at WOT would be incidental. Does this sound ill-advised, or like I haven't thought it thru correctly?- I think it would help my fan run stronger and safer at idle, and provide solid cooling at idle. thanks, m weiss