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Snowman

Alternator Interchangability

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I know that XT6 alternators can be adapted to fit on ea81 and ea82 subarus. How about a legacy or impreza alternator? Those cars are a lot more common, so alternators would be much easier to come by, as well as cheaper. Any ideas?

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I've got a perfectly good ea82 alt on my car, as well as one on my parts car. The issue here is power output, as the stock alternator is inadequate for running my offroad lights at low RPM.

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It's normal to have inadequate current at low rpm. Alternator will need at least 1500 rpm for reasonable output; 2000 rpm is better. Below 1500 your battery should have sufficient energy to keep your lights running. If not, you may have faulty wiring or a bad ground connection. Any decent alternator shop can change the pulley on a XT6 unit and mount the pulley for your EA81 or 82. This will increase the amp output at high rpm to 80 or 90 amps, but still won't do much for you under 1500 rpm.

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turn down the heater fan or turn off the headlights when it is idling.. check for voltage, do an amps draw test when the car is off, then whenits on. kowing a specific reading, you will determine if there is a short or a parasitic draw on various circuits

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I don't think that there is a bad ground or parasitic draw. It's just the fact that I have 510 watts of additional lighting installed. If there was something wrong, I think it would appear if the engine was running a bit faster, or when I was only running one pair of lights in addition to all the stock systems. I also have, at one time or another, had nearly every circuit in the car turned on with and without the engine running, and both the voltmeter and ammeter had reasonable readings, not indicating abnormal draws.

 

Here is the draw of my offroad lights:

4 100 watt lights= 33.3 amp draw

 

+2 55 watt lights= 9.2 amp draw

 

+ any power required to run the relays, switch lights, etc.

 

So we're talking nearly 43 amps when all the lights are turned on. The stock 60 amp alternator can handle that in addition to the stock systems when running above 1500 rpm, but at idle my ammeter is reading a 30 amp discharge with all the lights on in addition to the stock lights, the radio, and the heater on low.

 

So that it why I want to put on a bigger alternator. I would like to find out if a legacy or impreza alternator could be made to fit, since parts are readily available for those cars, whereas finding an XT6 alternator looks like a major feat.

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the early legacy (90-93) Alts are I think 75 Amps, and they are in the same housing as the XT6 alt. you will still need to have a v-belt pulley put on it, but it will fit the same as the xt6 alt.

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Kelly, what you are asking is not possible. Talk to any alternator rebuilder and he will tell you that the full output of any alternator whether it's 50, 60, 90 amps or more is only obtained at high rpm. Below 1500 rpm, the 30 amp discharge you see is what you're going to get regardless of the total output capability of your alternator.

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I definitely had that in mind, although not at the front of my mind. I'm just hoping to increase the alternator output so that the rpm when the charge is maintained is slightly lower, and so that the battery gets charged up more quickly when the rpms do increase.

 

I think the smaller pulley might spin it too fast, and I do a lot of cruising between 4,000 and 4,500 rpm, so I don't want the alternator to spin too fast.

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I know that someone has a Datsun alternator on their sube that has more output than an XT6 alternator but bolts on without mods (unlike the XT6 alt). However i dont remember an exact part number, if it was even given. Anyone have this part number?

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