Sound System

[JEden06]

I'm currently getting ready to do a false trunk in my MKIV Jetta. I'm doing two Alpine Type R's with two mono V12 amps but am having major problems with the lights dimming and what not because VW is cheap bastards and put such small alternators in. Is just a batter upgrade to a yellow top dry cell going to be enough to help power that system or is it going to be best to get my alternator re-spooled? Also, does anyone know where I can get between a 120-160 amp alternator for the MKIV Jetta 1.8T?

[VAG_Tech]

Re: Sound System

I'm not much on the sound side of things but, I found this on the net.

Quote from http://ccs.exl.info/elect_upgrade.html

Car lights dim when the bass hits? Unfortunately, the solution to this problem is not cheap or simple.

The electrical system in most cars is designed to supply power to all the factory-installed components and accessories. If you add power-hungry amplifiers, the car's electrical system can not keep up with the current demands. The car's components and your audio system are in a constant fight for the low power resources.

Capacitors

The first thing to do is to add a stiffening capacitor. A capacitor acts as a secondary battery that reacts very quickly to sudden current demands (i.e. music transients). A rule of thumb is to have 1 farad of capacitance for every 1000 watts of power. The sound system will sound a bit smoother and hopefully the light dimming problem will be either fixed or reduced. Your lights don't necessarily have to be dimming for you to have to add a capacitor. Stiffening capacitors always help a sound system.

Capacitors should be installed as close to the amplifiers as possible, with the positive lead going right into the positive lead of the amp and the ground to a metal part of the car (not to the ground terminal of the amp).

When a capacitor is first installed, it has no voltage in it, so if it is hooked up to a battery, it will act as a short circuit and draw a LOT of current (not a good sight). Capacitors need to be "charged up" first. This is simply done by either putting a resistor (1k-ohm or more) or a test light between the positive post of the battery and the positive terminal of the cap (with ground hooked up to metal). After a few minutes, the capacitor will be charged up, and it can be connected. Every time the capacitor is "drained" i.e the lights were left on in the car and battery is dead, the capacitor should be DISCONNECTED, battery charged, and then capacitor has to be recharged and reconnected.

Capacitors might help, but they do not take care of the fact that your car's system is underpowered. They are a "patch" for a more serious problem

High Output Alternators

Another upgrade is a high output alternator and maybe adding a secondary battery (for car off listening) to keep up with higher system's demands. This should be done by someone who has a fairly good understanding of a car's electrical system, since computers are designed to control the factory components.

Additional Batteries

Always keep in mind that when a car is running the batteries become loads that take power away from your amps. The advantage of secondary batteries is that when the car is off, you can listen to your stereo for longer periods of time.

Adding more batteries will not make your stereo perform any better when the car is running. In fact, a second battery will steal power from the electrical system when the car is running. A battery isolator should be used to avoid batteries draining each other.

Replacing factory batteries with high performance batteries will also improve power output. Companies such as Optima make batteries that take less power to charge and have a higher output, placing lower demands on an electrical system.

[Stonewall]

Re: Sound System

Capacitors won't do much for light dimming. The problem could be due to the size wire you ran to the amp, it you are running to much wattage the current will be limmited by the wire size. I don't think it is your alternator as the VW ones are quite good. I do think your battery maybe on its way out though it you are getting major light dimming.

[JEden06]

Re: Sound System

The stock VW alternator is only 70 amps. If I have 120 amps of amplifier's then there alone the alternator will not be able to ouput the proper amount of amps. Correct? Each amp requires 60 amps of power. So...Yea...lol

[Stonewall]

Re: Sound System

The stock VW alternator is only 70 amps. If I have 120 amps of amplifier's then there alone the alternator will not be able to ouput the proper amount of amps. Correct? Each amp requires 60 amps of power. So...Yea...lol

Depends on the car I believe. Most cars that have AC etc have bigger alternators. If you are drawing 120amps you sure as hell better be running 0gauge! So what you running 2000watts plus? might want to check out what you are actually pulling for wattage.

[Khyron]

Re: Sound System

Just because you guys are talking about power, does anyone know the cost of alternate alternators? I ask because the stock part is over 800 bucks and we're all going to need one sooner or later. You'd think it was made of platinum or something...

Khyron

[Stonewall]

Re: Sound System

Just because you guys are talking about power, does anyone know the cost of alternate alternators? I ask because the stock part is over 800 bucks and we're all going to need one sooner or later. You'd think it was made of platinum or something...

Khyron

Should almost never need to replace an alternator. Maybe replace bushings and rebuild it once but thats about it.

[JEden06]

Re: Sound System

I've had estimates to have them re-spooled so that they are bigger which is pretty much in a way rebuilding it anyways and that can be done for anywhere from $100-$150. You'll be without your car for a few days but it's better than spending $800.