Ground Loop?

[jsdevel]

I've been having some issues with noise and Batt V fluctuating between 12.5 and 13.7. Alternator is putting out a steady 14.5 V. 12.5V at the battery.

Here's how I have my setup configured:

Earthing Scheme.jpg

Should I reconfigure this so that each component of the system grounds directly to the engine instead of the terminal?

[billr]

Need more info. Where are the battery and alternator connected, relative to that "ground" symbol? What are conductor sizes (and lengths, if they are skimpy)? I'll assume all conductors are copper...

[jsdevel]

Ground symbol is engine. Battery ground is hooked up to opposite site of block. Wire is copper. Alternator is connected to engine and battery

6 16 awg wires spanning roughly 3 feet from engine to terminal.

4 20 awg wires from LS coils to terminal spanning roughly 4 feet

4 18 awg wires from injectors to p&h board via DB15 spanning roughly 4 feet

4 18 awg wires from p&h board to terminal via DB15 spanning roughly 2 feet

5 20 awg wires from ECU to terminal via DB37 spanning roughly 2 feet

[jsdevel]

Here is the terminal I'm using

5 Pcs Dual Row 8 Position Screw Terminal Strip 600V 25A + 400V 25A 8 Postions Pre Insulated Terminal Barrier Strip Red /Black 10 Pcs https://www.amazon.com/dp/B01DY73N2C/re ... MybEQ0FF5M

[billr]

You have all 8 positions jumpered with one of those red or black strips, correct? At the engine end of the AWG16 wires from the term block to engine, are those individual lugs on a single large screw/stud?

I'm not seeing anything I don't like, but would be tempted to try a heavy (a couple of #10s) "jumper" between the battery side of the engine and the MS side; even if just temporarily.

I'm still not clear on how the alternator is connected, but presume it is kind of "stock" and the grounding is through the alt frame/engine; with the output being through a "fusible link" (short piece of smaller wire) to the starter/ battery cable. I don't think there is a problem there, but just want to keep it in mind because your problem is kind of a voltage-regulation issue.

[jsdevel]

You have all 8 positions jumpered with one of those red or black strips, correct?

That's correct.

At the engine end of the AWG16 wires from the term block to engine, are those individual lugs on a single large screw/stud?

yes.

I'm not seeing anything I don't like, but would be tempted to try a heavy (a couple of #10s) "jumper" between the battery side of the engine and the MS side; even if just temporarily.

I'm going to give this a shot tonight with my battery jumper cables

I'm still not clear on how the alternator is connected, but presume it is kind of "stock" and the grounding is through the alt frame/engine; with the output being through a "fusible link" (short piece of smaller wire) to the starter/ battery cable.

That's exactly how the alternator is hooked up.

I don't think there is a problem there, but just want to keep it in mind because your problem is kind of a voltage-regulation issue.

It does seem like a regulation issue. The alternator supposedly has an internal regulator. My multimeter showed a steady 14.5 volts, but I suppose I should run it through my sound scope to double check.

[jsdevel]

Hmm. This doesn't look right. I hooked up the fused 12V supply and the terminal ground for the ECU to my sound scope and am seeing this wavy power source:

scope.png

Is this what a bad ground looks like? I'm going to hook the ECU directly to battery negative to see if that makes a difference.

[jsdevel]

So I think I've narrowed it down to my Innovative LC-2 WB controller. When I disconnect that the signal on my sound scope is almost flat. Very minor fluctuations (probably caused by noise from the scope itself). When I hook my LC-2 back up and power the ECU on with key in #2 position, I get the fluctuations again. Is this common with the innovative LC-2 controllers?

[jsdevel]

So the minor noise without the WB was due to cabin electronics (radio etc.). When I hooked my sound scope directly to the battery, I received a very nice flat line.

The voltage drop when the car is stationary was almost non-existent. A few mV at the most.

I'm still getting noise with the WB. After reading other posts and the manual for my WB, it looks like it would be best to power it directly from the battery.

I temporarily placed a 16V 2200uf cap between ECU ground and ECU +12V. Is this a recommended solution for dealing with noise?