Power Question for Camry

I have a 1995 Toyota Camry that has an alternator with a 70 amp output. I have just purchased a Phase Audio/Butler 475 (TubeDriver Series) that has a fuse requirement of 60 amps. As well, I am considering getting a MB Quart RAA2400 (subs) that requires a fuse of 90 amps. I will be running all channels at a 4 ohm stereo load. Currently, I have 4 ga. power and ground wire (including ground from battery to chassis) and a 1 farad power cap. I would assume that I'll have to upgrade the ga. of my power and ground as well. But my question is, can my alternator handle that kind of draw from my amps? I know they usually give the alternator a little more juice than needed, but is it enough?

Also, some input on the Quart RAA2400 would be appreciated. I am interested in SQ. What do you think of this amp? I know it has many RF components, but I figured if it was run to my subs and at a 4 ohm stereo load I wouldn't notice any lack of clarity. Is this a decent assumption? Also, the fact I can get it for $250 from an authorized dealer is nice as well.

Thanks

Since you are not going to be pushing those amps to their max capacity, you can halve their fuse ratings and go by that for figuring power needs.  So instead of using 60 + 90 = 150 amps, use 75 amps as your maximum pull.  The car has a 70 amp alt so you can see it already is too weak to power your audio system (at extreme levels) and that's not considering that the alt has to provide current for your car's needs, too.  Looks like you should be doubling that alternator rating.

Your 4 gauge power and ground should be sufficient for what you are going to pull...see https://www.the12volt.com/info/recwirsz.asp.  But you will want to look at the OEM wiring under the hood and upgrade any power and ground wires that are smaller than 4 gauge.

I'm not familiar with the amp in question so no help there, sorry.

Iraggi gets a nod of approval from the forum, although I don't have personal experience.

stevdart wrote:

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Since you are not going to be pushing those amps to their max capacity, you can halve their fuse ratings and go by that for figuring power needs.  So instead of using 60 + 90 = 150 amps, use 75 amps as your maximum pull.  The car has a 70 amp alt so you can see it already is too weak to power your audio system (at extreme levels) and that's not considering that the alt has to provide current for your car's needs, too.  Looks like you should be doubling that alternator rating.

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Can this be taken as a hard and fast rule though? The reason I ask is I used to have a 1990 Civic with the factory 70 amp alternator. I was using a PPI A600.2 on 3 JL12W6 (i.e. 4 ohm bridge) and an A300 running my mids/highs (4 ohm stereo). The A600 had a 60 amp fuse and A300 a 30 amp fuse (30 +60 = 90 -15 for the indicated load on the A300 = 75 amps). I did not have any power caps and used 4 ga power wire and yet I didn't experience any dimming of the lights, etc. The system sounded great! So does the efficiency of the amp make for an additional variable to the equation? Does this sound reasonable?

Understandably, I doubt this would apply to the amps mentioned for my current system, because I believe neither of them use a regulated power supply like my PPI amps did.  I'm just asking for my own understanding. With this logic in mind, perhaps if I used a JL 250/1 (30 amp & regulated PS) instead of the Quart amp it might work? Anyway, thanks.

bogey] wrote:

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an this be taken as a hard and fast rule though?

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Absolutely....NOT!  There are no hard and fast rules when it gets right down to it.  I just looked at a) your question, which indicated a concern, and b) your explanation of the way you will wire loads to the amps.  Then I used simple math.

]So do wrote:

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s the efficiency of the amp make for an additional variable to the equation?

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Not in this case, because you are already using the amp fuse rating as an indicator of maximum amperage the amps can pull.  The fuses are real, not an equation...so their rating takes precedence over figuring amperage pull using Ohm's Law and amp efficiency.  What I did above, though, is just take a guess by saying you could halve the fuse rating because you will be loading the amps at half their maximum potential.  It could be the case that the amplifiers are so well built that the fuse ratings far exceed the limits of loading, and so halving would not be the true case....maybe taking a fourth of the fuse ratings would be more realistic.

Wattage output (potential at the given load) / car's electrical system voltage X amplifier efficiency percentage could work here as a guide, too, for guessing at amperage pull at the extreme volumes according to your usage.  You would have to have a clear indication of the actual efficiency of those amps at your proposed loading.

Efficiency is also helped by the quality of the install, including and especially the subwoofer enclosure, as a larger volume of airspace will allow for more output of the sub with less power.  How you play your system is also a big factor.  If you are meticulous about settings, careful of using the volume knob and mostly listen at reasonable levels, the amperage pull will consistently stay on the low side.

Your math above looks right on and that should give you an indication of how your proposed new setup will go, too.  Experience > calculating knowns > guessing unknowns > throwing it all together with no clue!  As you can see, experience rules.  But your own experience is worth more than 100 other's.  For questions such as you posed here, especially when dealing with power requirements, I always look at the math first.  If it doesn't work, you'll know why.