Capacitor and alternator question

[Flipper245]

Hi folks. Just curious if a capacitor would help this. I have a 91 turbo firefly and managed to wedge a large case gm alternator in. Bought a cheap 250 amp off eBay. It seems to be keeping up just fine but on the tight, quick bass beats I'm getting voltage drop. Not much. Maybe touches down to 13 bounces up to 15 then settles back at mid 14. On the long hard notes it stays over 14. After some research apparently the cheap alts have slow, cheap parts in them causing a low slew rate. Basically making the reaction time of the alt really slow compared to the ones costing 3 times more. It dimmed my lights a bit too when the bass hits. I was thinking a cap could help this.

My sub amp is an Orion xtr2400 pro run at 2 ohms on a re xxx18. Front amp pg xenon 200.4 running actively mids and tweets so not pushing that hard. Probably realistically about 2500 watts if I find the right song. Car uses minimal power.

Any suggestions other that dropping $600 on high end alt?

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[Mitch86 5,000+ posts]

A couple of small batteries.

 

[Jeffdachef 5,000+ posts]

Big 3 upgrade along with an external regulator or XS power's Voltage control module. 2nd option may or may not shorten the life of your ebay alt.

 

[Flipper245]

Ok so I have 1 gauge from alt power to batt. Kinetic 1800. 1gauge alt bracket to strut tower grounding alt. 1gauge grounding batt to opposite strut tower. 2 4gauge power wires run to each amp since that's what the inputs are. Short runs since amps are under front seats. Amps are grounded under seat bolts right now but I will be doing the dual 4 gauge runs back to the battery.

I like the idea of the external voltage regulator. Will that basically bypass the internal electronics of the alternator?

I know my battery probably isn't rated for 250o watts but don't really have room for another. Besides it doesn't seem like the amps are dipping into the battery too much. Volts are staying higher than 12.5.

 

[wew lad 5,000+ posts]

Don't be fooled by that. Batteries will stabilize your voltage more than anything.

 

[n2audio 5,000+ posts]

Batteries have a LITTLE current available above 12.6, but not much.

Big battery might stabilize voltage a little, but it would do it as much by reducing peak voltage as increasing min.

Fact of the matter is it's almost impossible to have a rigid supply of 14-15v when you're drawing 200A+ peaks.

A big cap might actually improve your voltage reading, but it won't help the performance of the system -- either the sound or electrical.

 

[LosIsATool 5,000+ posts]

Batteries have a float charge but it's minimal. It might be enough to take a hard hit or it might not. Don't rely on it working.

Alternator power is the key. Batteries with fast charge/discharge rates are important. That's why one good battery is better than 2 cheapos

 

[Flipper245]

Thanks a lot for all the advice. I did cheap out on the electrical a bit to get this sub working. It is probably bare minimum. Truth is this system cost me very little collecting if over the last couple years. So I think I will get a second kinetic 1800. The one I have has worked great. I'll put one behind each seat and run them together. Weight and mounting option with this car is an issue. The amps are under the seats so this should work good. As far as the alternator goes, maybe I can put some higher quality parts in it instead of getting a better one. The amps are 3200+ watts rms so maybe 250 amp isn't big enough.

My alt is grounded to strut tower. Once the batts are in back should I run a ground from batteries up to that alt ground to complete the circuit? Not sure I trust the body of this car.

 

[big scott]

im running a cheap 200 amp alt and i dont have charge lag....

 

[Flipper245]

Hmmm. And a lot of batteries by the looks of it. One issue for me is weight. My car started out as a 1700 lb sports car. Having an all aluminum motor up front means the front is very light and now has a 160 lb box in back. That's one reason amps are under seats. Try to keep the weight off rear tires. That's why I was asking about capacitors. Didn't want to add another 50 lbs. I might just upgrade those grounds and leave it at that unless I can wedge another batt up front. I'm really happy with the sound and it's way more than my ears can handle anyway. Lol

 

[n2audio 5,000+ posts]

My car started out as a 1700 lb sports car.

WTF??? Do you drive an indy car?

 

[wew lad 5,000+ posts]

Hmmm. And a lot of batteries by the looks of it. One issue for me is weight. My car started out as a 1700 lb sports car. Having an all aluminum motor up front means the front is very light and now has a 160 lb box in back. That's one reason amps are under seats. Try to keep the weight off rear tires. That's why I was asking about capacitors. Didn't want to add another 50 lbs. I might just upgrade those grounds and leave it at that unless I can wedge another batt up front. I'm really happy with the sound and it's way more than my ears can handle anyway. Lol

loud systems and lightweight don't mix, not yet anyway. good subs are heavy, good amps are heavy, good batteries are heavy, good wire is heavy.

 

[big scott]

go with maxwell caps if you want to save weight.

 

[Flipper245]

Never heard of maxwell caps. Going to look into that but I'm leaning towards the battery idea. I think I can fit a few of the small ones under the hood if I arrange them properly and build a bracket to hold them. There's no room for another kinetic 1800 under hood. I think a member is selling sets of 4 of some small batts. That might be the way to go. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Nice comment on the Indy car. I wish. They're rest engine I think. Then I could build the sub into the front and point it right at my face! Lol. It's a 1991 Chevy sprint with the optional turbo upgrade from the factory. They weren't offered in U.S. I wouldn't consider it sports car in stock form but with a bit more boost and some work to the suspension it is very capable. Actually it handles like a go cart. The way the box sits now is affecting the handling. It puts the woofer inverted with the magnet a couple inches from the roof. That's a lot of top weight in that little car. I'm going to add on to the old enclosure hopefully soon. My spare tire well is cut out and dropped about 4 inches. With the whole rear behind the seat glassed in on top of the spare tire well I will have about 7 cuft. Woofer will be flush with top of seat sloped down to bottom of hatch. I want this thing to not be seen. Then the magnet will be about 8 inches from pavement. It will be lighter and no more top heavy. I'm sure the car is over 2000 lb now.

 

[Flipper245]

Just an update. That cheapo 25o amp alternator only lasted about one month. Don't think it was putting out 25o either. I put the 140 amp power master back in that was running the system for two years when it was only 2000 watts. I added a second 140 amp power master. Also wedged 4 of those hawker batteries michaellane was selling, under the hood. Rewired everything. Rebuilt box. Voltage stays above 14 and doesn't budge except a tiny bit on the largest hits. Very relieved with that! Thanks.