Yesterday I had installed the Megasquirt PNP PRO for my 04 Mazdaspeed Miata. Only 2 settings have been changed, Overboost Protection at 177 kPa(~11psi) with both Fuel and Spark cut and Rev limit to 7000 instead of 7200.

I notice for night time driving there is a significant notice drop in voltage when on the throttle or idling. Two things to verify it were all lights dimming and also my Cigarette lighter splitter has a voltage sense and it shows 4 lights. 2 red(Under 12v and 12v), yellow(mid/normal) and then green (high).

Before the megasquirt installation, the stock ecu handled the voltage just fine and all 4 lights illuminated with no noticeable drain spike besides when A/C kicked on for a split second.

Youtube vid here of difference

 

what does your battery voltage look like when you datalog?

 

is MS controlling your alternator? Could just need a more aggressive duty curve.

 

Well I ended up not looking at the logs, but the basemap gave 13.5 "run" mode volts while Alt charge sat at 14.0. I turned up the "run" volts to 14.0 and charge volts at 14.3, overrun I kept the same. That ended up solving the issue in the end.