Can my 83's stock alternator handle a 500watt mono amp--->400watt rms 12" sub without any issues?
If this helps:::

http://www.rockfordfosgate.com/produ...n_US&p_status=

http://www.rockfordfosgate.com/produ...n_US&p_status=

THANKS

 

Alternator output is usually based on vehicles options , i.e. current draw to feed accessories .

 

You will be just fine, just make sure you run the recommended size wire directly to the battery, make good connections, make sure the ground is good etc.

 

change in plans, I'm gonna use a 300w amp, p300-1... that will draw 16amps average from my alternator. with my car running AC, both fans, and lights, should have enough free space for 16amp? And I'm gonna use a 1 farad capacitor

 

Personally, I would ditch the cap unless your stereo is only for rattling windows at traffic lights. In practice, your battery and alternator should be able to do the same job. At least try it first without.

Also, if you haven't already, measure the voltage output from your alternator to see how it's doing. Mine would charge weakly when it got warm after the car had been running, but changing the voltage regulator (a $20 VW part on the late ones, at least) had it back to supplying a solid 13.5V+.

 

Alright, I will try it without the capacitor first, and thanks for the tips!!

 

If your amp draws 16amps that means it consumes appx. 220watts of power at max (16A X 13.8V = 220.8 watts). About the same as 2 sets of 55watt driving lamps.
The capacitor is useful in larger set ups to help smooth the voltage because low end can pulse.
The best way to see if the alternator can handle the added load would be to run the car with all accessories running and take a current reading to see what the max load is and then subtract that from the alternators max capacity which should be 115amps for you car I think. If your total load is at least 20amps less then the alternator's capacity then a 16amp additional draw should be ok. Keep in mind you'd have to have the system full ***** to the wall jammin to require the full 16 amps so it's norm might be a bit less.
Also, a 500 watt amp running at 2/3 capacity will have more headroom, be less likely to clip, and run cooler then a 300 watt amp running full out.

 

I think it's important to state that this would pretty much only be possible with an amp-clamp... certainly not possible with your garden-variety multimeter as measuring current with a DMM requires breaking the circuit and then closing it through the meter in series... which could be complicated to do safely with a car's electrical system, and even if you did, the meter's fuse would blow.

I just don't want to see someone trying to measure 115A with a handheld DMM.

 

Good point and very true, I should have been a bit more specific about that.

 

No it's not. The Cap in a car audio system is of zero benefit, and is just audio jewellery, that only sell because people keep perpetuating the urban myth that they are of benefit. Save your money.

I am running a 4 ch amp that puts out 1 x 500 and 2 x 125, so a monobloc shouldn't be a problem, but I would look at a class D amp(if that one isn't) as they draw very little current for their output, and so place very little load on electrical system.

Make sure you fit a quality fuse holder(not a cheap chinese one) at the battery, to protect the car, and minimize voltage drop.

If you have any other questions let me know
peace
Cyberpunky

 

Agreed on the good fuse holder , I've been in electronics for 25+ yrs , and I've even seen a Monster Cable fuse holder melt down . Quality piece , but too much draw for a standard fuse , had to move into an "ANL" type holder .

 

time for a thread jack, if the PO installed a cap with the stereo, what's the best way to remove it without replacing the power wire all the way back? I was thinking a heavy duty fuse holder and higher than needed fuse.

 

And even worse: they're heavy! Seriously, I wish the "stiffening" capacitor would go away.

Of note to the original poster, though: I believe that the early cars had 70 amp alternators, or somewhere in that range. Later ones had 90s. Their output falls off at idle and as they get hot, too, and if your alternator is only supplying around 12.5V and your contacts aren't good, your electrical performance won't be very good.

All to say that you should clean up your contacts and check the alternator. All it will take is time, and it may even help your car run better!

If you'd prefer not to have the extra bulk, you could also use a butt connector with some heat shrink or other electrical insulation over top of it once you tighten it up (here's a 4 gauge example, but they come in a variety of sizes):
http://www.amazon.com/Mobilespec-Gau.../dp/B002U5Q9RG

 

The early had a 90amp alternator, late 115 I believe... Getting the 500 watt amp will draw more power, so wouldn't the 300 be better? I'm planning on ordering the amp tomorrow

 

pkt1213
you dont want to add a fuse as having 2 fuse(same value) doubles the amount of current before fuse blows or doubles amount of time. Better to do as suggested and use a butt connector or a distribution block. Butt connectors with 4 awg will require some pretty serious tools to crimp, so distro may be better as no special tools are needed. Make sure it is safely insulted as it will be a live wire and a fire risk if not properly insulated.


Butters944
in theory at full output yes but as pointed out in another post, using the bigger amp, but with gains set conservatively, may not draw any more current, but will give you more headroom(ability to play dynamic peaks), where as the smaller will need to be driven harder so may draw more current and will have no headroom for peaks.

If you think of it like a V8 vs a tiny 4, then where the small 4 is getting thrashed the V8 will be barely ticking over. Sure you can crank the v8 and get more power and draw more current/suck more juice, but you can also keep it cruise mode and end up with better economy/less stress.

I would go the bigger amp and keep your gains down or matched, so you have headroom, as this will tend to give you more punchy bass and you are less likely to clip amp, and so is actualy safer for your speaker than using smaller amp, as its drivng an amp into clipping that kilss most speakers(from not having enough power and pushing to hard) rather than too much power cooking them, as most speakers can take more than rated at if it is for short periods, as we get wen playing music.

hope it helps
peace
Cyberpunky