Yes, it will perform better. Most alternators already put out about 13.8v as it is.
If the alt isn't putting out 13.8v, sometimes there is a voltage regulator near the amp that you can adjust accordingly. However, most (if not all) of the new alts have the regulator located inside of the alt.
The stupidest answer to that question. A cap will not help steve. If your voltage is dipping too low, like 12v and under, you'll need a HO alt for the voltage and current you need.
Steve, that is a really bad sign, you need to keep the volume low until you get a HO alt, there is no other solution to your problem. You could be damaging your amp and your subs, be careful.
To me i read somewhere if the car's engine is off then only 12 volts is available but when the engine is running @ above 1500/2000 rpms then the voltage automatically goes up to 13.8 volts ....
Some amp manufacturers catch ppl by listed a higher wrms & in small writing u will see thats only when the amp gets 14 volts ....
I rebuild my alternators. It's all in the voltage regulator for the voltage. I run 14.7v @ 1,000rpm, with a 160 amp stator. But stupid me, I forgot to get new brushes, so I need to get on that...