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Discussion Starter · #1 ·
I just purchased a 2019 Subaru Impreza hatchback, my very first Subaru ever… I’m not impressed at ALL with the stock radio or the speakers, I installed a dash camera front and back and next is a compustar remote start and alarm, then I will upgrade the audio, to a degree of over the top, im going to be driving this car every day for the next 6+ years and I want to enjoy the audio, my equipment I have from my Mazda 6 is being carried over ( besides door speakers) I had to upgrade my alternator to a 250 amp and big three upgrade the vehicle, now I need to do it to the Impreza but I could only find alternators for old model Impreza (early 2000s)… Does anyone have any info on where I could find one for our car? I had to search for years to get one for my Mazda and I really don’t want to do that again… This car is begging for upgrades and I can’t find anything to supply my gear. I’d love to share with you all my modifications, if anyone could point me in the right direction I’d be very happy, naturally..
 

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...upgrade my alternator to a 250 amp and big three upgrade the vehicle, now I need to do it to the Impreza but I could only find alternators for old model Impreza (early 2000s)…
Beware that modern charging systems use a 'current sensor' on the battery-negative terminal. The alternator output is controlled by the computer based on current-draw from battery.

Adding a "big three upgrade' without understanding how these modern systems operate can be disastrous. It is all too easy to inadvertently bypass the current-sensor with the wires. The computer will NEVER sense any current-draw and your battery will not get charged at all.

I suspect this is why aftermarket alternators which work seamlessly with the modern systems are hard to find.

Perhaps a better approach for you to take is to calculate your average current draw after adding additional electrical load. In this way, you will better understand if the factory charging system will need any modifications to meet demand.

It is possible that you may not need to upgrade the factory charging-system.

BTW: The 'current sensor' mentioned above also dictates how your additional electrical load should be connected into the charging-system.

Again.... ANYTHING connected directly to the battery-negative terminal will bypass the 'current sensor'. (hence the computer will not know when to turn on alternator.)
 

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Discussion Starter · #3 ·
Beware that modern charging systems use a 'current sensor' on the battery-negative terminal. The alternator output is controlled by the computer based on current-draw from battery.

Adding a "big three upgrade' without understanding how these modern systems operate can be disastrous. It is all too easy to inadvertently bypass the current-sensor with the wires. The computer will NEVER sense any current-draw and your battery will not get charged at all.

I suspect this is why aftermarket alternators which work seamlessly with the modern systems are hard to find.

Perhaps a better approach for you to take is to calculate your average current draw after adding additional electrical load. In this way, you will better understand if the factory charging system will need any modifications to meet demand.

It is possible that you may not need to upgrade the factory charging-system.

BTW: The 'current sensor' mentioned above also dictates how your additional electrical load should be connected into the charging-system.

Again.... ANYTHING connected directly to the battery-negative terminal will bypass the 'current sensor'. (hence the computer will not know when to turn on alternator.)
3500 watts is more than the stock alternator could supply with the rest of the load of the car, 130 amp is what I was told that came factory from alternator shops near me. Very odd that a computer needs to “turn on” an alternator, my 04 Mazda had an ECU controlled alternator and big 3 went fine on that, the computer system in the Mazda 6 1st gen surprised me with how extra it was for its time. I’m sure things are even more intricate on these Imprezas but I’ve never heard of an alternator that turns off and on.. like an ac. Is there a clutch in these alternators or something? I’m generally curious, I’m not trying to be a smart ass.
 

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Is there a clutch in these alternators or something?
The alternator is enabled/disabled ELECTRICALLY. (no clutch required) This is done with PWM (Pulse Width Modulation) signal into the alternator.

i suggest you do some more research regarding how the 'current sensor' integrates into the charging system.

Many folks have tripped over the operation of the modern charging systems until they actually put a voltmeter across the battery and MEASURED that the alternator-output will go up as various electrical loads are added.

Conversely, when the alternator is turned off, the battery runs everything. This is all thanks to Federal emission-controls and efficiency-standards.

Some examples:
  • During acceleration both the alternator and the AC compressor are disabled so more engine-power gets to the ground.
  • During decellation, the alternator is turned full-on, to help re-capture some of the forward motion into the battery.

Infact, I believe some folks took the time to monitor the alternator under various conditions in an attempt to better understand the algorithm which controls the alternator.

3500 watts is more than the stock alternator could supply
There is NO WAY you can draw that much current constantly with sound-system. Lets not forget that audio amplifiers draw very 'spikey' instantaneous currents. The AVERAGE current draw is far less than the rated amplifier output power.

Hence - Your alternator only needs to be able to surpass the AVERAGE current draw. (The battery supplies the spikes)
 

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Discussion Starter · #6 · (Edited)
A 250A alternator? Holy f*ck, what kind of current draw are you expecting? Are you powering airport landing lights with it???
JP23 by down4sound monoblock 2300watts rms (not peak) and a Memphis Audio MXA850.5 five Channel for door speakers, I don’t think I’ll really reach the peak on the 5 channel since I’ll be running it at a lower gain for my door speakers to handle. 250A isn’t really a lot compared to stuff I’ve worked with and saw in the past. I might just add and change the battery under the hood and add a second battery to the trunk. I’ve only worked in older model cars and nothing modern so these modern charging systems are making my head hurt lol. I always want to have reserve power to keep voltage at a comfy 13.7-14 volts. In the Mazda with a 270amp alt with 1800w (2400 peak) mono block and 360.4 kicker four channel I would see voltage drops as low as 11v on the highway with music playing. Audio systems take a lot of power.
 

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Discussion Starter · #10 · (Edited)
I know brand x does because i recently contacted them about it. But im sure mechman would too
I was on their site and couldn’t really find much of anything. Would you happen to have a link directly to the alternator? I don’t know why they don’t have it easier to browse their site or I’m just blind.
EDIT: is this the one you are talking about? I think I found it in their site but I’ll keep browsing. Please correct me if I’m wrong. Very vague description.. are we two or three prong plug? Lol I haven’t checked
 

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I was on their site and couldn’t really find much of anything. Would you happen to have a link directly to the alternator? I don’t know why they don’t have it easier to browse their site or I’m just blind.
EDIT: is this the one you are talking about? I think I found it in their site but I’ll keep browsing. Please correct me if I’m wrong. Very vague description.. are we two or three prong plug? Lol I haven’t checked
I'm not sure all I know is I hit them up through Facebook and they were more helpful them their website
 

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Discussion Starter · #12 ·
I know brand x does because i recently contacted them about it. But im sure mechman would too
I'm not sure all I know is I hit them up through Facebook and they were more helpful them their website
cool thanks, I sent them an email so hopefully I’ll get a response back. I just hope these alts bypass the charging regulation.
 

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.....
EDIT: is this the one you are talking about? I think I found it in their site but I’ll keep browsing. Please correct me if I’m wrong. Very vague description.. are we two or three prong plug? Lol I haven’t checked
That alternator is clearly marked as being for the 3.6l 6-cyl motor. Better make damn sure that all the connections are the same, or be ready to make new wiring...
 

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Discussion Starter · #18 ·
Hey i just ordered one from brand x. Its a 250 amp for 450.
If you could cancel the order. Nextgen alternators has 350 for $479 with 12 diodes and fans for cooling also if you want you could get a powder coating done. Sorry I didn’t reply back the holidays had me on my ass for a while. I didn’t even reply back to next gen let alone update you.
 

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Discussion Starter · #20 ·
I didn't get a chance to cancel it but man I'm not disappointed at all View attachment 27204 View attachment 27205 View attachment 27206
That is so sexy!! I still haven’t gotten an alternator yet, life happened and I’m saving up for a whole audio overhaul because base level impreza has the worst sound I’ve ever heard in a car and I’m an installer at Best Buy, I’m embarrassed to have it in my car. I’ve done a remote start/alarm on it which was fun though.
Are you getting any battery lights or check engine codes? I doubt it but it’s worth asking.
God damn that blue is so sexy though…
edit: did you have to change your belt?
 
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