how big of an alternator

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twobig86

Copper - Posts: 84

Joined: November 30, 2005

Posted: September 12, 2007 at 10:53 AM / IP Logged

Hi, I finally got back from Switzerland about 3 weeks ago and my brother and I bought a car off our friend. A 93 Honda Civic SI. Now I finally got around to ripping out the old audio system and want to install my own.

My Question is this. I need to purchase a new alternator and I dont know how big it is. How can I find out how many amps my system is drawing. I have no idea how big of an alternator I need, here are the items in my system that are drawing power:

2 x MTX T9512-44 Subwoofers (Dual Voice Coils, 12”, 1000 watts RMS each)

http://www.mtx.com/caraudio/products/subwoofers/thunder9500.cfm

2 x MTX TA81001 Monoblock Amps (1000W Each at 2Ohms)

http://www.mtx.com/caraudio/products/amplifiers/thunder81001.cfm

1 x Clarion APX640.4 – 4 channel Amp (4 x 80 RMS watts)

4 x Clarion SRX1384 – 5 ¼” Speakers

So just my audio system is drawing lets say 1000w + 1000w + 320w = 2320 watts (I know amps are not 100% effic)

so if I have that kind of pull from the audio with all the other regular car systems how many amps do I need to run the system and still charge my two Optima batteries. (Think Im going with 2 red tops)

Also I have Kicker 0 Gauge wiring kit (300 amp fuse) as my power wire from the batteries. Is the 300 amp fuse enough or should I go with the 350?

Lastly do I HAVE to get a custom made alternator or can I just ebay one from say a truck and fit it into my car? Any thoughts on the matter would be helpful, as custom made alternators are pricy

Thanks in advance for any help.

haemphyst

Platinum - Posts: 5,054

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Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: September 12, 2007 at 11:56 AM / IP Logged

The 1000 watt amps are digital, yes? 80% efficient. So, 2000w/.8=2500 watts in (sub amps, only)

320W/.6=533 watts in (highs amp)

2500+533=3033 watts in / 14.4v = 210A

That's what you need just for the amplifiers. The Si also had power stuff - windows, defroster, A/C, fog lamps(?)...

My 07 Civic, just to run, with NO accessories turned on, requires about 10A, high-beams bump that to 32A, A/C bumps it to 70A (with the fan on high), turn signals, brake lights, and defroster running, too? I can easily go to 100 to 110A with the stereo just turned on, and playing at a reasonable volume.

Not being completely familiar with the 93 Si, I can't say you COULDN'T stuff a large case GM 300A model under the hood; I know in my 86 Si, there was PLENTY of space for a bumped up alternator.

Call over to HOAlternators, 866-446-8878, and ask for Phillip at extension 106. That guy knows his stuff! I'm betting they can make, or even have on the shelf, a bracket mod for your car.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

jvillefinest

Copper - Posts: 255

Joined: December 29, 2003

Location: Florida, United States

Posted: September 12, 2007 at 2:18 PM / IP Logged

im pretty sure the rule of thumb that i have always been told is wattage/12.5 (vehicle voltage) with that said your is somewhere around 185 amps.

2320/12.5=185.6

not 100% sure on that but a 200amp should do you well although good luck on finding one for a civic

2007 Acura TSX

SQ setup in the works

haemphyst

Platinum - Posts: 5,054

Joined: January 19, 2003

Location: Michigan, Bouvet Island

Posted: September 12, 2007 at 2:35 PM / IP Logged

jvillefinest wrote:

im pretty sure the rule of thumb that i have always been told is wattage/12.5 (vehicle voltage) with that said your is somewhere around 185 amps.

2320/12.5=185.6

not 100% sure on that but a 200amp should do you well although good luck on finding one for a civic

That's figuring 100% efficiency, which amplifiers are not. Also, you are not allowing for accessories, which I have done. 200A won't be big enough, especially if, as I said, he likes to play it WFO.

Also, H-O-Alternators, as I suggested above, DOES have a 200A alternator, even for my '01 Civic. The early 90's Civics also had PLENTY of room under the hood for upgrading their alternators to a larger case, like the GM 300A I suggested.

It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

jvillefinest

Copper - Posts: 255

Joined: December 29, 2003

Location: Florida, United States

Posted: September 13, 2007 at 5:56 AM / IP Logged

ahhh should have read your post more closely...

2007 Acura TSX

SQ setup in the works

twobig86

Copper - Posts: 84

Joined: November 30, 2005

Posted: September 16, 2007 at 10:28 PM / IP Logged

Awesome thanks for the responses guys. Im going to give that guy over at HO Alternators a call sometime in the next 2 weeks....im so busy at the moment that I just dont have the time to work on the things that I want to work on...

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how big of an alternator

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