Quick Alternator Question

motocross_masta

Registered User
If I'm going to run my subs w/ the MRD-M500 amp, its only gonna pull something like 13volts of the alternator, is there gonna be any problems w/ that? What if i get a set of Underdrive pulleys? Thanks, any response is greatly appreciated.
 
Add a stiffening cap/farad capacitor, at least one full unit/ 1farad.

This will help significantly. The amp you're using tops out at about 950 watts. Be sure to use 4.ga power and ground. With the underdrives, you may have some worries with loud play during idle, but shouldn't have any trouble when driving. Hope this helps ya. Alyn.
 
Caps are useless, don't bother wasting the money

Either upgrade the alternator, or do the easier things first
 
Well moto-masta.. Its not really the voltage that matters, rather its the amount of power that the amp will pull at its peak level. The math is fairly simple. If a 120 Watt amp puts out its peak power continuously, then it would need 120W/12Volts = 10 Amperes of current. 10 amps is nothing for the stock alternator. Your radiator fan draws about 70 amps peak, but then backs off as it spins up.

Now, when the car is running, the voltage is around 14V. And if you've got say a 500W amplifier, then the max current is more around 500/14 = 35.7A which is significant, but still not bad. But keep in mind that the current has to feed any other accessories you have running at the same time! The stock SC alternator is rated for 110A. So, 20 for the headlights, 30 continuous for the cooling fan, 20 for the windshield wipers and 35 more leaves you near the maximum capacity of the alternator.

Realistically, it will rarely need to provide that much power all the time. What most people do to smooth out the peak loads is install a big capacitor near the amp. It acts like extra storage for sudden power loads.

Any car stereo shop should be able to tell you what size cap would be good and if you even need one. You just need to tell them that your alt is rated at 110A.

And when you get it done, do me a favor and try to avoid driving by my place with it cranked up late at night ;) ;)

Good luck.
 
Tazer, how you gunna say a cap is useless? Did you ever open an amp up and happen to see the internal capacitors? Capacitors make up the main power supply stage for the amp, and when they run dry, you get the dimming lights and other problems because the main power draw is now being taken from the battery, and fighting with the car for power. So with caps, the more the merrier.

A good example was with my old car, my corsica, i didn't use caps at first. Now, the car had a 105amp alternator. I upgraded the alternator to battery wire to 4 ga. and same for the battery to ground. Helped at first, but still had problems with the battery voltage falling to 10.5 at the amp and 10.9 at the battery. I added 3 caps, and bang, no more dimming, and voltaged never fell below 13.9. Keeping in mind these amps I was using were unregulated, took what they wanted, and played louder with more voltage.

Just as well, the general rule is 1 farad for every 1000 watts. My genaral rule is .5 farad for every 30 amp fuse the amp has. Beffing an alternater, or hot rating it, will do nothing more than kill your battery that much faster. Unless of course you plan on doing multiple batteries such as 2 or 3 optima red tops or equivalent gel cell's. If you wanna start with the easier things first, upgrade to a gel cell battery, ie. orbital, optima, etc. Then upgrade your power wire between your battery and alternator, and ground wire to the chassis.

Tbirdscfan, I thought our alternators were rated at 130amp. Wasn't 110 for the n/a v6?
 
No, I don't agree. If you upgrade the electrical system to not need a cap, you are going to have to install very expensive components and waste countless hours on something that you don't need and isn't cost beneficial. A cap fits the budget perfectly. That's like saying for safety's sake, the steel structure of an automobile is a bandaid and what needs to be there is 1 inch thick steel all the way around. It's not cost beneficial! If you install the right gauge wire that the amplifier manufacturer recommends, then you will be alright most of the time, except for peaks. Which is where the capacitor comes in. And you would have to be listening to your stereo at full volume at all times to need that kind of electrical system. That makes me think that as I frown on all the people that drive past my house late at night and wake up my kids, this is all the more reason that I need to start investing in hearing aid companies! I have been running one amplifier that can draw up to 80 amps at peak with 4 gauge wire for power and ground with the stock alternator for about 5 years with no trouble. Yes, my lights dim when at full volume bass peaks, but I would have to agree with Pearl95SC that I would benefit from installing a cap to take the brunt of the peaks. But, with wife, buying anything for myself now seems impossible. Now whether the 110 amp stock alternator is sufficient, I would venture to say, yes, for most applications. How long will it last? Well, that depends on how loud you listen to it and how often. My recommendation, install the amp with the right gauge wire, then listen to it and see how bad the lights dim. If they do most of the time, then get a cap. My .02.
 
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Well, it's more so than anything, that the system won't be the culprit in killing the alternator, but if the system and the car use more juice than the alternator can produce, it will lead to a certain death. This is why a cap is usually a good thing. Most systems i've installed have never seen a cap, but god only knows it sure would have helped. In my sc, i was runnin the mtx 8100d, metered it at 2384watts, going to 4 RF HX2's, peaking out at 151.3db, no cap, 4ga instead of 0ga, and no fuse either. Stupid, yeah, did the amp ever see its full potential, no. There was times with this setup, that I would be turning the corner, and the rpms would come down, and the car would stall. If the system wasn't on, no problems. Are caps really needed, depends on what you're running. But, they will always benefit a system. The improved voltage allows the amp to run cooler and play cleaner. And that has been a proven fact.
 
pearlsc. Our alts are actually the higher rating at 110. The 6 cylinder N/A engine has an 80Amp alternator with the smaller 4-rib pulley. At least when I replaced mine, thats what the various parts houses had listings for. In fact, they spent quite a while even finding a part which was supposed to fit. They showed a few different brands, but my 90 SC came with a Mitsubishi 110A internally regulated alt.
I ended up getting a rebuilt Duralast from Autozone (actually 3 of them, but thats another story) which I had to order by part #. Fortunately, it came with a bench test printout curve of RPM vs output current at a constant 13.5V. They ran it to 110A which was reassuring. This one has held up fine so far.

For those who like the math, this works out to be roughly 1.4 KW of power (Volts x Amps) or enough to power a good hair dryer. But that 1.4KW has to run all the SC's accessories at the same time. My puny 180W tube doesn't begin to load it down. ;)
 
capacitor pros

better power supply regulation via better filter capacitance
is proven to improve transient response, imaging (sound stage)
and noise performance in better audio systems...of course none
of this REALLY matter if the license plate is rattling with each downbeat....
CC
 
I am afraid Tazer999 is correct on this subject.

http://www.eatel.net/~amptech/elecdisc/capacitr.htm

http://www.eatel.net/~amptech/elecdisc/caraudio.htm

A capacitor will assist in smoothing out the voltage spikes which occur to your accessories from the power supply of the amplifier suddenly starting and stopping large current draw. It will do nothing to alleviate the lack of output of an alternator insufficient to supply necessary current to all running loads.

That being said, you generally can't damage anything more than your alternator if you run an amp with too large a current draw for an extended time. So if you think it does not produce enough current for your amp, just try using the amplifiers and be prepared for a possible alternator failure. That way it will not catch you off guard and strand you anywhere.

The site www.caraudioforum.com is to car audio what the SCCOA is to SCs. :) You can find the answer to nearly any audio question there, the abundance of technical knowledge is incredible to say the least.
 
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Which part are you saying that Tazer is correct on? If it's about a Cap being useless or just being a bandaid for a weak electrical system, then I'm afraid you are going to have to join Tazer in the "wrong" corner. Yes, the car audio forum is a great place to learn about car audio, but just like here, you can recieve some "not-so-good" information. But, to each his own. By that I mean that a lot depends on what you are going to load the alternator with and how much can the alternator handle. I don't think we all are disagreeing about everything, I think the previous comments were made by Tazer assuming that he was going to install ten, 100 amp continuous draw amplifiers. In that case, yes, the electrical system is WAY too weak to supply power from a 110 amp alternator. But, if you are going to install a 20-40 amp continuous draw amplifier (which should cover most people), then the factory one is just fine. But, on a rainy day (windshield wipers going), headlights on, rear window defrost on, etc. etc., and the stereo pumping, then you might get your headlights to dim. What he needs to do is figure out what all his car accessories draw with all of them on. Then add in the maximum amount of draw the amplifier can muster. Then find out if it's over 110 amps. If it is and he doesn't listen to it at full volume, then he's going to be alright. I already gave him an example of what my amplifier draws at full volume and for how long. I just don't think that he (or me for that matter) is going to find the answer is the posts you provided. And I fail to see where Tazer is right and the rest of us are wrong. Please educate me, because I know for a fact that I am decreasing the life of my alternator by loading it down sometimes (play it loud). But, to me it's worth it. I am an audiophile. And I think that if the amplifier was too much for his electrical system, then I think the car would stop running before the alternator would just die. The truth is, you can damage more than the alternator. If you install a smaller gauge power and ground wire than is recommended by the auto manufacturer, then you could torch the car! If that happens, I don't think you are going to be worried about your alternator anymore! Anyway, the links you provide are nice, but a tad bit lengthy. Here's the true test: Go to an authorized MTX dealer that might possibly sell the MRD-M500 and ask them if the system in your SC will run it okay. See what they say and please report back. According to a couple of you guys, an upgrade to the alternator is the only way. I (along with others) am just saying that you can do that, but a capacitor is a viable, way more cheaper and sensible solution.
 
Several of the points you mentioned which I will attempt to provide a relatively brief response to, for sake of reading time :)

First, about Tazer's comment refering to the capacitor as a bandaid to a weak electrical system: What I think he meant was that it will not correct or help an overload condition on an alternator. This is true, because a cap is nothing more than a temporary storage device. Like a water tower, it can act as a buffer in that a large electrical draw will take from it rather than the alt, but then it must refill. If alt does not produce enough, the cap will eventually run dry. These processes occur in seconds when dealing with the large current draws found in car.

Next, you implied that with the power of his chosen amp, the stock alternator will likely be fine, maybe challenged at times of highest acc use. I agree. It takes a relatively powerful amp played at a good volume for a good percentage of useage time to really exceed alternator output. Most ppl do not have car audio setups like this. And for those time when accessories are on full w/ amp at high volume, he will likely be ok if alt output is not greatly exceeded for long. Again however, if it is, a caps storage will run out quickly. It can not store enough reserve power to make up a possible alternator lack of output even temporarily. Calculating the current draw of his amp & matching it to available current is a good way to determine what will happen, but like stated it is likely fine with that power level.

Third, the alternator can be damaged from extended draw over its rated output, as I mentioned earlier & as you have. However, as far as components damaged from a large amplifier taking more current then available through the cars electrical system, the alternator is really the extent of the possible damage. Wiring issues are seperate. Anytime you have a large unfused wire, there is a possible fire hazard reguardless of alternator or amp ratings. Like I say, if there was an instance where amp draw exceeds alt output, it would be fine to just play & see. Only the alt could burn out from this, and it just means it needed upgrading anyway :D . As for smaller wires, they won't hurt anything (as long as they are fused) but the amount of power your amp will get will be less.. so output could be less. It would be little more than a waste to have a good powerful amp and a 20 gauge wire to power it. Only a significant lack of output from the amp would result.

To recap, first I should say my intentions are not to be on the offensive here. I like car audio, and hence its discussion. Basically the use of caps to compensate for electrical system inadequacy is just something that I see happening a lot, but know it doesn't help in that circumstance.

In this circumstance, I do agree with you about his amp power in ratio to his stock alternator, I think it is fine too, even on those rainy days. A cap could serve to protect his other sensitive accessories from the regular voltage spikes which occur as the amplifier draws and stops drawing current.

Someone I know has an MTX amp producing 500 watts @ 2 ohms pushing 2 10" 6k series on a stock alternator setup in conjunction with amplified mids & highs just fine.

There is something you could do short of replacing the alternator to help if an electrical system is found to be inadequate.. upgrade the magic 3! These are the various ground wires found inside the engine bay, and can make a significant impact!

Nice discussing with everyone...
 
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Yes. I concur. With everything except the smaller wire issue... If you have a much smaller power and ground wire, say a 10 gauge (power) wire running a length of 17 feet for arguments sake, and you are running more amps than what is recommended based on a wiring chart (they use them in various applications other than car audio if you do a search on the internet) for that length, then you risk melting the wire and possibly catching fire. You have to be careful about the smaller wires, they might burn you! Even if it's fused correctly! I believe that the amplifier will still try to draw the current it needs, but yes the output will be significantly diminished.

And tell me (and probably others) about this great idea of upgrading the "magic 3"! I'd like to do that! I never really thought about that! Do tell! What size are they now and what (realisticly) can you upgrade to? Nice!
 
The 'magic 3' is a reference to the main ground wires found inside the engine bay. These wires connect from the Alternator to the battery, from the battery to the engine block, and from there to the vehicles chassis. Most vehicles have these basic connections, though I have heard of some having more, and some w/ less.

Among car audio enthusiasts running higher powered amplifieres, it is usually common to upgrade these wires to 4 or 2 gauge, depending on length needed. This usually produces very noticeable positive results on the capacity of the vehicles electrical system, and helps make the best use of your equipment.

I am unfamiliar with the origin of the nickname.
 
....

ok, i have a couple things to add.. I've been doing car systems for years.. and i'm an Electronics Tech at work..


MY Secrets about a True good System Setup

To do the whole system correct, look below

for your system:

Power/Ground Wire -
High Strand wire gold plated or silver, oxygen free wire so its very flexible..because your using alot of amps, and amps flow on the outside of the wire, the more stands the better flow, bigger gauge less resistance. use the same size for both. ground should be less than 1.5 feet for best results. use inline fuse (add up the fuses on all your amps and go with that rating)

Battery -
a low internal resistance battery, so when it needs power it gives it. i preffer optima yellow top, there pretty good, yellow top is made for repetative , charge/discharge.. some other brands also.....
* if you want to go with a really nice setup and better, run one in the trunk with an isolator between both batteries, unless you use 2 of the same batteries.


Cap - (Capacitor) (get a digital one)
you need one, (alot of places say, at least .5 Farad for 500 watts, this other place i go to says 1 farad for 500 watts, bigger is better) i go with that one also... for when you hit the low bass it peaks out and draws a big amount of current and you need a cap for the spikes because a battery wont be able to keep up, it will just end up with distorting or robbing power from other source (lights dimming). a regular non digital cap will last about 1 year of constant use, they dont last to long unless u get a digitial cap, then again those only last about 4 yrs or so before there gone also..

Alternator -
Correct thing is to upgrade, your alternator is your heart for your system. you should upgrade to provide the right amount of current for your whole system. if you do, i would upgrade the alternator wire to a 4 gauge stereo one, (high stand wire, gold, silver or platinum plated, oxygen free for best current flow.)

* tip 1
use sparkplug grease for all terminal connections for best current flow with low resistance

* tip 2
Do all of these uptop if you want to do it correct


Alex LaChance

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