voltage issues with MS2

[yellowlt1ta]

Hey guys I've had my MS2 for years and since the beginning I've always had voltage issues. Its on my 1993 trans am.
I have installed a new alternator and still same thing.
I have used a known good alternator from my truck and still same thing.
I have tried to run the car at idle with only the battery and still the same issues.
I have tried to use different battery's and still the same thing.
I have removed the LC-1 just to make sure its not an issue with that and still same thing.

here's the run down: MS2 v3.57 on a 350 lt1 sbc wasted spark LS coils
low z 95lbs injectors batch fire (I have used these same ones on a friends mustang SVO and a microsquirt the voltage was perfect) EBC from DIYautotune.

I have remade the entire wiring harness to meet all megasquirt recommended specs.
battery is in the trunk with a good solid ground the MS2 is grounded to the engine (7 ground wires) the engine has a good solid ground to the chassis and the alternator has its own ground to the chassis as well. all sensors have grounds to the MS2. everything is by the book.
so far I can only suspect the problem to be with the megasquirt it self or the LS coils possibly as they have their own power and ground, 12v supplied from alternator and ground to its own battery post. As far as the low z injectors its possible that because I have 8 of them and the car I tested them before only had 4 that it could cause an issue. I can swap to stock injectors just for testing but I just dont feel that its the real problem here.

I will attach the msq and logs for your viewing.

AFRheadsLJMScam.msq

(118.71 KiB) Downloaded 26 times

batteryonly.msl

(391.39 KiB) Downloaded 19 times

voltagetruck.msl

(1.38 MiB) Downloaded 25 times

[kjones6039]

I doubt that injectors have anything to do with your voltage problems. What I will say is, your charging system doesn't appear to be working, according to the logs you posted. I would concentrate my efforts there. There is also the matter of the random voltage dips in both logs. Grounding issues would be my guess at first view.

Ken

[yellowlt1ta]

the previous logs were test without the factory charging system. thats why it seems off.
here is a log of the vehicle with a new alternator, new battery, and new charging system wiring.

2017-10-09_17.16.13.msl

(1.18 MiB) Downloaded 27 times

it spikes to 16.7s and drops to 10.8v that is my problem. I cant seem to pin point.

[DaveEFI]

Lo-Z injectors driven PWM (no series resistors) are known to cause voltage spikes - sometimes. There is a PCB mod to help with this. I think it involves adding a second +12v feed to a spare pin on the DB37 that goes straight to the injector drivers only. A search on here should find exact details.

[Matt Cramer]

Lo-Z injectors driven PWM (no series resistors) are known to cause voltage spikes - sometimes. There is a PCB mod to help with this. I think it involves adding a second +12v feed to a spare pin on the DB37 that goes straight to the injector drivers only. A search on here should find exact details.

Here's the mod details:

1. Cut the center leg on Q9 and Q12 or desolder it so it does not reach the PCB.
2. Run a length of jumper wire from the center leg of Q9 and Q12 to an unused pin on the DB37 connector.
3. Wire this pin to a 12 volt source in the wiring harness, separate from the Megasquirt's power supply wire.