chief455

iTrader: (21)

while logging I see my volts drop from ~13.2 to 12.9 - usually higher rpm, I also have my 2nd fuel pump activated by boost.

1.) Concern for tuning?

2.) I see voltage stabilizers $20-$90 - anyone use this and see they work?

MontecarloDrag

iTrader: (3)

Your alternator may be on it's way to oblivion

With engine running, check if the voltage you see while scanning is the same at battery terminals (meassured with a voltmeter). Sometimes they don't match because PCM grounds are not good.

If they match, it is a concern. It may be your alternator going bad, a short or a bad ground.
If battery voltage is higher than the one you see in your datalog, check for PCM grounds or add a ground wire from battery (-) to PCM case.

99Bluz28

iTrader: (35)

At what rpm does this start to happen?

chief455

iTrader: (21)

~4800-5000 and returns to 13+ volts as soon as I let off throttle

gofastwclass

iTrader: (2)

I agree with MontecarloDrag, it sounds like new alternator time.

My lights would get dimmer the higher I revved the engine and the voltage never went above 13 when hot.

I use truck 140 amp alternators.

chief455

iTrader: (21)

As a starting point, I bought an alternator.

I have already cleaned all grounds and saw ~.50v increase under all driving but high rpm.

Hopefully after install, I'll see volts stay above 13 at all rpm's.

If not, and even so - I think I'll get a V booster for +70% TPS that can only help when it is really under full load.

I have a coil per cylinder and second fuel pump all pulling volts.

I'll post up results.