my hypothesis

[tylerj 10+ year member]

So, I drive a 99 lumina that has a stock 100 amp alternator. I read that most cars use about 80% of the stock alternators amperage output. I found Cop alternators for 99 luminas that put out 140 amps, for $75 a piece, which is rather affordable for me. I was powering a 400w rms sub with my stock alternator and my lights were dimming a little bit, so I figure my safe max with my 100 amp alternator would be roughly 500rms.

If I put in this cop alternator, I will have an extra 40 amps, would I be able too power 2/3's more then with my stock? as in 1500w rms?

if you follow me, let me know if Im dead wrong or not >_>

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[michaellane 5,000+ posts]

with my 107amp alt in my 2002 accord with 1200rms and 4gauge wire i didnt dim...just double check your grounds and maybe get your alt and front battery checked out...id say with a 140 amp alt you will be more then fine with the power youre running

 

[groundpound4200 5,000+ posts]

I've ran a hell of a lot more power on an alternator that size but I had a huge battery bank

 

[Databyter 10+ year member]

I'd take a look at your wiring. Lights shouldn't be dimming even with your old alternator. Assuming 14 Volts and MAX amp output your only pulling 28 Amps to power your sub. call it 35 for slop and peaks.

Make usre your're cable is adequate and connections clean and tight.

And not just your aftermarket audio power cables, but your battery clamps, cables, and chassis ground etc. Also your battery should have some reserve power to draw from, the alt can't anticipate peaks and if paired with a poor battery you will still have problems.

I'm pushing twice that much with a stock 90 alt and I've no problems with dimming. The stock wiring on my Subaru is tiny and I haven't done the big 3, but it is clean and tight until I do and it's working. Of course the stock 90 alt is brand new, and my amp power cables are adequate.