350xfire

iTrader: (1)

Hi guys, I have a 1980 I want to put a decent system in and was wondering what the limitations of the stock alternator are?
What I want to put in it is:
1. 4 channel amp
2. 4 speakers- 6.5s and 4s
3. one 10" sub
4. Mono amp for 10" sub- may be around 500W
5. Single Din head unit

Will the stock system power this? I will not have any other electrical stuff other than stock items.
Anyone have pics of installs in '80?
Thanks

DivinDriver

iTrader: (15)

Consider that the majority of stereos in the 80's were 10-20w / channel. Subwoofers didn't exist.

KansasCityREPU

iTrader: (9)

With a system like that you need to upgrade the alternator and also think about adding a second gen under hood fuse block. All new power lines for amps and new speaker wires.

t_g_farrell

iTrader: (1)

Definitely will need more amps from that alternator. The stock alternator only puts out 50amps.

350xfire

iTrader: (1)

ok, thanks, is bigger alt a simple mod?

KansasCityREPU

iTrader: (9)

I believe the S4 is an easy swap but the S5 can be swapped and only requires a little extra wiring at the plug.

DivinDriver

iTrader: (15)

S4 is electrically a direct drop in but mechanically uses a different length spacer where it mates to the pump housing, so if you are getting a used one make sure you grab the spacer too... or you can use a stack of high-strength washers wrapped in colored tape like I did, lapping the last one down for a perfect fit.

350xfire

iTrader: (1)

Thanks, I have a lathe so I can spin up a new spacer. How much better is the S4, amp flow wise?

Thanks

LongDuck

Umm, not to jump in unnecessarily - but you guys realize that just throwing a larger battery in there and letting the alternator recharge the battery is how this works, right?

You're not running your stereo system (incl. subwoofers or amps) from the alternator - you're running them from the current stored in the battery - which has far more power behind it than your alternator does. Upgrading the alternator only makes sense if you're continually draining your battery.

I run a 400w amplifier and a 10" Bazooka tube in the back of my -SE with the stock alternator and the smallest Optima Yellow-Top that they make - it's so small that when I bought it the guy behind the counter told me it would never start my car. He's wrong - because a rotary doesn't have a lot of compression to overcome. That said, it runs my stereo system just great and it's not because of the alternator. Good luck,

SolarAbby

iTrader: (1)

I had my battery die in my FB after driving in the rain at night, wipers on, stereo full on, and every thing else electrical on. The alternator just couldn't keep up with all that and the battery just ran out.

I now have an S4 Alternator. No problem since.

DivinDriver

iTrader: (15)

Both are important; the alternator has to be able to keep up with the continuous operating demand AND provide enough charge current to recharge the battery after peak demands (like starting) or else the battery eventually runs down as mentioned by SolarAbby above.

Battery's like a bank account. Alternator's like a paycheck. Total income has to meet or exceed total outlay or you end up with a balance of zero.

You can run a car without a battery, provided the alternator can keep up with operating demand and you jump-start it. You can run a car without an alternator, so long as adequate charge remains in the battery.

TheRX7Project

iTrader: (3)

My alternator couldn't even handle when I switched to an e-fan LOL

Yes the alt is a simple swap. There are at least 3 write-ups on how to wire it.

LongDuck

Actually, you can't run the car without a battery - as the battery provides the stored amperage needed to power the coils quickly. The Alternator is rated in amps output, but can't provide the current needed to power the coils.

Test this by starting your car and then unhooking the battery terminal - it will die - even though the Alternator is connected directly to Battery + and grounded through the engine and wiring harness.

The analogy about the battery being the bank account and the alternator being the paycheck is close, in that as long as you have enough charge current coming in, the account remains fluid. Too large an alternator can cook a battery and overload the charge control circuitry, while too small a battery will result in hard starting (slow), and possibly issues with not running heavy stereo demands properly (clipping on base, cut-out, etc.) if it can't provide the amperage draw needed.

If you're going for big amplifiers, invest in a bigger battery - and THEN, if the battery can't keep up look at the alternator upgrade to supply the battery with better recovery. YMMV,

DivinDriver

iTrader: (15)

Could'a fooled me, Duck... because a couple months ago I watched a guy drive a newly-acquired AE86 home without a battery in it; seller had no battery. Jump-started & left connected until the engine warmed up, insulated the positive cable so it couldn't short to ground, and off he went. Drove several miles to a parking lot where his other car was waiting.

First hand experience says it worked. Jaime G, "Battlecat" from here on the forums was the driver.

Cookboy

iTrader: (10)

I've done it in a '57 Karmann Ghia. 40 years ago, but it worked.

rotor motor 85

iTrader: (1)

You can run a car without a battery trust me. The way i have always tested alternators and batterys without a tester is start the car then disconnect the positive if it dies it has a bad alt. If its still running then the alt is still putting out voltage which means its good. Its a crude way i know but i have diagnosed many cars on the roadside using this method.

LongDuck

Well, your experience has been different than mine, as I rescued my brother in his Infiniti Q45 because it had a dead battery and shut down while driving. Could have been a bad alternator on his car, but I never heard back on it. Still, if you kill the engine while you're driving and can't get it spinning - you're dead right there. Not a way I'd want to drive a car.

rotor motor 85

iTrader: (1)

Oh i agree i would never drive a car without a battery unless i absolutely had to. But it can be done but needless to say its not good for the electrical system or the alt. Weird to hear that it didnt work on the infinity but not really surprised all of the newer cars and their electronics are increasingly becoming more dependant on one another. Thats why i still drive stuff from the 80's easy to diagnose.

DivinDriver

iTrader: (15)

On this, we agree 100%. & there are some driving modes (high rpm & lights/wipers on) that could possibly overtax the alt & may overheat it or end up stalling out.

Plus, unlike with a generator, you can't push-start an alt-equipped car without a battery, as the alt coils need excitation current before they will produce any power.

ATC529R

how do i save this thread lol.

Here's what I have for my build now.

Kenwood 8" subs
Kenwood 6x9s
(enclosure made where the rear compartments are for these)

6'5 kenwood front speakers in front doors
Kenwood head deck
Kenwood amp for the subs
Kenwood 4 way amp for the 6.5 and 6x9s

It's about 1,000 watts between the 2 amps. I think one is like 150x4 and the other is 200x2


what alternator do I need????? this is for an SA build that has no poer options.

ATC529R

oh, and i intend to run a yellow top batery with 770 CCA. (v-8)

DivinDriver

iTrader: (15)

1000 watts load at 12VDC is 83 1/3 Amps... Just for the stereo. I = P/E

But you're talking maximum output power, I suspect. (Which is also likely given is Watts RMS which is AC, so power factor plays into it too - but no need to cloud the issue)

You need to know maximum INput power (Watts) or maximum current draw (DC Amps) for the amplifiers and head unit.

Then you need to add the maximum load for the rest of the car.

midnight mechanic

350, crutchfield.com for info on upgrading to a sub woofer.

StumpDrummer

Go to a reputable Alt shop and ask if they can put the 100 amp guts in your Alt if so do it, it shouldn't cost much more than a stock rebuild if you have a system pulling 75 amps which is on the lower side of amps for a real system a 100 amp Alt should work just fine!!....Now if your going to do something like 6 peavey 15's: 4, 6X9's: 2,4's :and 4 tweeters let me know how you did it...cause its my next impossible task!! I do love it when they say Impossible! yes I said 6, 15's

SolarAbby

iTrader: (1)

The FB alternator body is pretty small compared to FC alternator bodies. Won't that make it a problem to put in 100 amp guts?