komodomoe

Ok, so it occurs to me that many people out in the world who are trying to do speaker mods lack electrical knowledge. I recently came across someone purporting that he had a 6000w system in his Accord. The problem with that is there is no way that this is possible. Before you go out and buy a big amp that supposedly puts out ungodly amounts of power, I wanted to share a little science with you so you would know what you'll actually be getting and not spend money on stupid things.

1) Watt did you say?

A watt is a measurement of power equal to Volts x Amps or roughly .00134102209 horespower. This is useful on many levels because you can calculate engine power draw from your electricals as well as the actual output you can handle. All cars (for the most part) run a 14 volt electrical system meaning that the alternator produces 14 volts at x amps to charge the 12 volt battery and power the electrical system. Some light airplanes use a 28 volt alternator and a 24 volt battery but that's irrelevant. My point is that your electrical system has a given potential output that is governed by voltage and amperage. Voltage in the car stays constant so the only thing you can change is the amp output with an alternator that handles a higher load.

2) I find your lack of knowledge re-volt-ing

So volts can be thought of as water pressure in a hose and amps as the width of the hose. That's why you can hook 1000 car batteries wired in parallel to a headlight and it wont burn out but if you wired in series, enjoy the fireworks. When you wire in a sub-woofer, you use heavy gauge wire to handle the amperage rather than the voltage. That's why you have these thick wires running to your sub from a 14 volt system but your home electrical cords that move 120 volts are thinner. (think about distributor wires, they carry upwards of 35,000 volts, that's why the insulation is so thick)
Bottom line, the higher the wattage, the higher the amperage because your voltage must remain constant. If you were to put a power transformer in that changed your 14v into 28v you could run wires that were half as thick but this would be somewhat more cumbersome than just punching a 1/2" diameter hole in the firewall (and let's admit that this makes us all feel a little bit more manly).
**Ampacity is a measure of the amperage that can be carried by a certain thickness of wire. This is dependent on temperature, but 4 gauge is 70 amps at 60 Celsius (hot hot hot) which will power a 1000w sub system at full blast for the most part. Ampacity also decreases with temperature, so, uh, keep that in mind.
(1000 watts / 14 volts = 71.4 amps)

3) I have the power

So you have a 2000 watt amp and you know enough that 4 gauge won't do the job, so you buy 0000-gauge which has an ampacity of 195 amps. So now, at 14 volts you can carry 2730 watts of power which you think will be fine. You would be, that is, if your electrical system could even make 2730 watts. To give you some scale, that many watts is just over 3 and a half horsepower, so before you figure in mechanical and electrical inefficiencies from the pulley, friction, and alternator itself, you have cut down the engine power on your Honda Accord by over 2%. That means 2% less power to the wheels, slower acceleration and higher fuel consumption.

4) I don't care, it's 2000 watts

But it's not, and here's why. Let's say your stock alternator puts out 105 amps which I believe is what the '01 Accord puts out. Ok, remember our equation? 105 amps x 14 volts = 1,470 watts. That is the TOTAL output of your alternator. So that is the max power you can give to the whole electrical system and we aren't talking at idle, that's max output at a good RPM. Lets also remember that this electrical system is powering your fans, lights, ignition, alternator field, ABS, Fuel pump, relays, VTEC solenoid (just kicked in yo), other speakers, ECU, Cruise control, Iphone charger, eFleshlight, sensors, clock, stereo system, climate control, and your sweet underglow. Say you turned everything off. Well, you still aren't getting 1,470 watts to the subwoofer because of those inefficiencies we talked about. It's like the difference between brake horsepower and wheel horsepower. If you're blaring you're radio, running the AC, and loading up the power steering system, your engine may be making 150hp but only 137 may make it to the wheels.

5) In conclusion, yes, I used that as my transition

-Before you dump a whole bunch of money on a whole bunch of watts, remember that the power handling of the system is irrelevant if you can't produce it.
-Make sure you're alternator can handle the wattage AND THEN SOME! Remember, you're powering more than just a speaker and the output at idle is significantly less than what the alternator is rated at.
-Finally, remember that drawing max load on the alternator shortens the life immensely. It's better to go overboard and get an alternator that makes 300 amps when you're using 150 than cheaping out and buying a 160 amp alternator. The rating is only the alternator's potential output, meaning that it will dish out whatever you want but it will only take as much power to run as you're demanding from it. The alternator is turning mechanical energy into electrical energy and the more draw is on it, the harder it is to turn.

PS: capacitors are meant to protect your system from voltage drops for short bursts if your alternator doesn't have the instantaneous draw for a big hit and in no way are a fix for having an alternator that is too small to handle the power output.

Thanks for reading, I hope this was of some help.


https://www.dcpowerinc.com/articles/truth-about-idle
http://en.wikipedia.org/wiki/Ampacityhttp://en.wikipedia.org/wiki/American_wire_gaugehttp://en.wikipedia.org/wiki/Watt

Mikeyymann

All Verry true thankyouu for tellin people how it really is

bumpstick

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