caballo77

iTrader: (1)

Hi folks:
I have an 04 wrx and am planning installing two amps:
1) a 200w class D (draws 28 amps MAX) , Infinity brand, will power a sub.
2) one MTX Thunder 40 watt RMS x 4 channel (States 40 watts MAX draw).

My question is:
Has anyone run similar wattage on their stock alternator?
Have any ill effects?

I know this is a pretty tame system but I am concerned nonetheless....
any advice appreciated.

pdqwrx

iTrader: (3)

You will be fine......Enjoy your system.

AzN121184

iTrader: (17)

what speakers are u running if u dont mind telling.

ldivinag

iTrader: (3)

remember, unless you are running a sinewave through your system, you wont be using the full power of the amps.

one sign when the system starts to drag is when at nites, you can see the headlights dim when hitting deep bass. and your charging cant recover fast enough, it will start to drain the battery.

remember, when your engine is running, all the power is from the alternator. when your electrical loads starts to overcome the output of the alternator, the battery will backup it up.

then when the load overcomes both the alternator and the battery, the battery will slowly lose it's charge.

too bad a voltmeter isnt a standard meter...

caballo77

iTrader: (1)

thanks for the input, folks.

the speakers are infinity reference components 6,5 front and 5.25 rear (IIRC).
the head unit is a pioneer deh7500mp.

funkdrmr

Everyone here has the right advice for you. Just couldn't help but give my example. 2000 watt RF amp to 2 Eclipse subs and I NEVER had the lights dim at night. The stock alternator will hold your setup just fine.

asianboy101

im sorry but i have to disagree here. you are actually using the battery first and when it drains the alt is recharging the battery. here is a good test for you if you dont believe me. while the car is running with no electrical power source running like stereo or headlights, remove the positive cable from the battery. you will notice the car die. there is a longer explaination but that is the easiest and simpliest one for now. but basically it is the battery that is running not the alt running the car. alt only recharges the car. a better alt recharges faster and more efficiently. a better battery recharges faster, holds a better charge, or may have more amps.

ldivinag

iTrader: (3)

i guess all of the previous 10-15 years of my knowledge has been wrong.

FWIW, in older cars where there isnt any computers, you can do that test in order to test your car battery. but in current cars, doing that could fry the ECUs since one of the functions of the battery is to filter spikes.

another function of the car batt is to start the car. remember, back in the old days, the cars started with a hand crank. when the car is running, the batt becomes a load on the alternator.

asianboy101

there are more safety measures, so i would not worry too much about frying the ecu. i have done this before. but as to the older car comparison i dont understand the correlation? i dont want to sound like a know it all its just that i have done this test before.

OneManArmy

iTrader: (7)

ldivinag is dead on correct.

Undo your positive? You crazy man. What does that prove? That you are disrupting the flow of power through your car..that's it.

You do not run off your battery. If that was the case there is no way in hell a battery could last 10 years and what not. The battery starts the car and you run off your alternator/motor produced power. Your battery is just part of the flow pattern at that point. it hands extra loads and spikes in power...like bass hits. blinkers, high beam flashes...horn honks...etc.

when your alternator goes bad how long does the battery last? not long.

If your were running off the battery you couldn't jump start a car. You'd have to have the freaking cables hooked up for like an hour to ge the battery to take a charge. I mean you can take a nearly dead battery and still drive your car if you had too. Do a direct alternator jump.

Man I got to stop before I get carried away....asian dude. You are VERY wrong.

Group B

iTrader: (3)

iaperformance.com is selling a higher-amperage JDM STi alternator, and you could have a shop build it for more power too...

AzN121184

iTrader: (17)

how do you like those infiniti's in the front?

i think they come with tweets for the 6.5's right? did u have to get tweeter brackets for them? Thanks

caballo77

iTrader: (1)

Azn:
I found the infinity were a great imprvement over stock but still needed some help, especially in reagrd to bass.
So I coated the interior of my doorpanels with some Dynamat and also a liquid product called QuietCar. This really helped with transient vibrations and allowed the speakers to play at a higher volume without unwelcome buzzing.

One note is that the inifity have a protruding woofer surround/foam and therefore you should really trim any plastic from the inner speaker grill that might ocntact the speaker. In short, I am very happy with these.

I also love the Infinity basslink which is a small subwoofer but since its servo driven, the 200w rms amp drives it without any problem.

caballo77

iTrader: (1)

Azn: Sorry I did not completely answer your post...

the infinity come with sepate tweeters and crossovers. I set the crossovers to -3db for the tweeters since they are already pretty bright.

I had the factory upgrade speakers when I bought the car so used the stock tweeter mount brackets and simply fastened the new tweeters to those, in the stock location.

VRWRX

I don't know. Even with only my stock subwoofer under the passenger seat, my map light will dim when the stereo is only at 12. The headlights obviously don't but dome/map lights do. I guess I just wanted to make sure you were just talking about the headlights...