What is the most wattage you can get out of stock electrical?

 

Are you meaning how much wattage can you run on the stock alternator? If so it will depend on amplifier efficiency.

 

yeah pretty much

I mean lets say an amp is 100% efficient, how many watts can it put out at 70 amps? I think that's the stock alternators output

 

My 2.2L alt is 115amps. Yours should be too. I have no issues with my near 900 watts of unefficient class ab amplifiers. BTW no amps are 100% efficient. Class D is very close at around 70%-80% typically. Class D is that efficient from lower levels to full output while class ab amps are only their most efficient at full output. Below that they are less efficient.

 

Watts = volts x amps

If the alternator can put out 115 amps, then

Watts = 115amps x 13.6volts = 1564 watts (theoretical)

However, you need to deduct all current draws from the car in normal operation (usually around 25 amps with lights on).

The alternator max rating is only for a brief period (maybe a few minutes at most) because it would overheat. A more reasonable number would be about 60-70 watts continuous draw. Some aftermarket alternators have additional cooling to allow more continuous amps. Also, the alternator output is lower at low engine rpm such as idle. The max rating is usually at a higher rpm. Again, aftermarket alternators are available that have less output dropoff at idle.

The resistance of the wiring in the car becomes an issue as current goes up (due to voltage drop). Even the heavy gauge battery cables could drop a few volts if current gets high enough.

Audio loads are not continuous but are a variable load ranging from hundreds of amps peak to a few amps during quiet parts. The car battery helps supply the short high-current peaks, but there is always the stock wiring limitations for high current. A capacitor located close to the sound system will help with current peaks.

Steve