Ugh... WRX and Alternator Upgrade.

by dflock
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Welp. I went down to my Subaru Dealership and talked with a mechanic there. Who then called Subaru Technical (the big shots). The mechanic called today and stated that the alternator could not be upgraded because it could cause the ECM (Computer Module) built into the car to be unstable. This totally sucks, cause I've spent a bunch of money on good audio gear that I am going to have to sell because I won't be to use it! Has anyone ever heard of this reason for not being able to upgrade an alternator? It just doesn't seem to make much sense to me. I don't understand how Amps from an alternator can effect the computer system?! Ugh... I'm totally bummed right now. I just figured I'd let some people know my story. Does anyone know anyone who has a WRX and has upgraded their alternator?! Strange.


Replies (13)
Tray on 07/7/2003 14:41:59
You should check into a power programmer. Companies like diablo sport, and hypertech have programmers to customize the settings of your ECM, or BCM, depending on what your manufacturer calls the computer.

They may have something which would allow you to re-flash the computer after installing a new alternator.

Swez on 07/7/2003 21:01:37
Personally, I don't believe a word of what you heard at that dealership. Yes, the ECM/BCM do have circuit controls that help manage Alternator output and distributes appropriate I/O data and signals to devices that control car performance parameters etc. But I am suspect of that answer you got from this dealership... try another soruce for a 2nd opinion.

There is a 2nd option you might want to consider... add a dedicated secondary ALT and battery for your audio system. Might have to get some creative help fabricating a mount and finding space to mount the additional ALT... but others have done that with good sucess... just takes a lot of planning and maybe some preofessional assistance to get it right the first time.


PS Don't give up yet... the game ain't over til the "fat lady" sings!

My guess... they don't have one to sell that fits your vehicle and gave you the old " blowing smoke up the anal pore" answer! I have never heard anything like this answer in over 3 years of doing this gig.

dflock on 07/8/2003 08:58:06

I wouldn't believe what they were telling me either, except that the mechanic that I talked with is my Uncles brother in law. So he knew me and actually took the time to call someone to get this information. Hmm... personally I bet I could put a bigger alternator on there with no problem, but I don't want to destroy anything on my car.

I am going to write an e-mail to Subaru directly, and see what they have to say about the situation. I am also going to try and find some people who has a system in their WRXs and see what they have done about their alternators.

I'll keep my chin up. But I suppose if I have to, I will just go all SQ in the car and run a small sub amp.


Relax_The_Mind on 07/9/2003 04:10:54
I honestly dont think car manufacturers are going to degrade car computers to have all the necessary protection circuits. The thing that an electrical component only draws the current it needs and nothing more. I am pretty sure on a newer car such as your WRX would have all the necessary voltage regulators and current limiters not forgetting about the fuse bank.

Not familiary with subaru so I may be totally wrong.


dflock on 07/9/2003 09:02:43
I left Subaru an e-mail with my question concering an Alternator upgrade. They just crapped out a stupid answer saying "any changes to your car may effect your warranty, so we do not suggest..." I left them another e-mail explaining that I really want to know if there is going to be a problem or not. Ahhh!

At this point I might just pull everything out and put performance parts into the car. But I really would like a nice sounding system in there.

dflock on 07/9/2003 09:05:13

Do you have any idea where these power programmers can be found? Any website links? I checked out, there might be some good info on that site. People discuss in forums about the changes or how to change things on Subarus.


Tray on 07/9/2003 10:04:44
I have no idea if they make then for the Subaru's or not, but

I also have heard of superchips, fastchips, and there may be others that I don't know of.

FYI - I called Chevrolet today, just to see what they would say, and I got a very similar response. "The Blazer is set up to work with the current alternator. Upgrading to a 130amp or more could short things within your electrical system, or cause engine failure."

Now I know this isn't true, but I also am not as close to the Chev guys as you are to the guy you spoke with, so I don't know how much was laziness in checking it out for me, and how much was, as Swez referred to it, blowing smoke up the anal pore.

ryan on 07/9/2003 14:44:28
Just go to yahoo or another search engine and type in Subaru WRX, cuz i was tryin to find a used one and it will show a couple forums just for that car. Might wanna give it a try.

dflock on 07/9/2003 16:13:08
I'm going to look into all this further. There is a very respectable and professional AutoSound Dealer/Installer in my area. I plan on taking a ride down there and see what they have to say, they may have done a system in a WRX and may have further information for me.

dflock on 07/9/2003 16:23:25
Check this link out:

Does that make sense? I don't really do electronics.

Tray on 07/10/2003 08:31:43
Does it make sense - Yes and No.

It is a good idea to upgrade the wiring from the alternator to the battery, and the ground from the battery. Will it definitely net you 2 volts? Probably not. It will help in the case of dimming lights, etc..., but won't 'upgrade' what is already there.

Swez on 07/11/2003 15:24:12
Am sorry to hear that you are getting this kind of runaround at Subaru. But unfortunately, most new car makers take a similar stand on alterations to the vehicle during the warrantee period. It's pretty much standard practice in the industry and negates any liability on their part to fix something that went wrong based on what you did on your own accord.

To understand electricity and current crawing devices, a given system can only put out so many watts of power to feed the load. If that load is exceeded, other parts of the load will be starved for power and begin to react in predictable ways... Ie: light dimming, slow blower motor speed and the like.

Now, ALTs have regulators that limit the amount of current x volts = watts that they can provide to the vehicles electronics. Primarily, the alternator has 2 main functions:

1. Recharge the battery to a fully charged state

2. Supply adequate watts to all electrical load devices as demanded by the devices when needed

The electrical devices wil only draw as much current as is needed for them to function. If a device fails (say a short) and draws too much current, it is fused and the fuse will blow to protect the rest of the electrical system from melt down.

Your options:

1. Continue to research this issue until you get the answers you need

2. Determine what the maximum load on the electrical system is for all devices being used all at the same time (count up all the fuse values) This will tell you how much potential reserve current your electrical saystem was designed for and how much reserve power is left over

3. You can alway add a larger capacity storage battery and larger gage wires to provide greater current draw for your amplifier(s) and keep the same Alt

4. As for adding a larger output Alt, there may be some issues between the ECM/BCM and the ALT that are not easily identified. The ECM controls many sensors and engine control functions to insure the car is operating at preset factory standards.

5. Use high efficiency amps that draw less current, but still have adequate output to power your system.

6. Install a 2nd ALT/BAT and wires to run only your amps

Figuring out the connection between these modules and the power supply system may be difficult without help from others that have really studied these things. I wish I could help direct you more in this one... but my experience with what you are dealing with now, is a bit beyond my knowledge base. But the responses you are getting on this board, are a lot more helpful than those at the dealership level.

In short, stay with it a bit longer and see what you can drum up outside the box... then we can all learn something from what you have learned.


dflock on 07/14/2003 09:08:39
Thanks for the feedback Swez.

My feelings right now are to go with options 3 and 5. Upgrading guage of wire from alternator and upgrading the battery. I'd like to keep the costs of the project down for now. I will see how the stereo sounds once everything is installed. And from there I will make a decision on whether I need more SPL or not. I feel like a SQ car might be more for me anyways.

I've had such issues with my stereo in the last few months that its driving me mad! But I am just going to bite down and get everything fixed / organized, then finished.

I had originally planned on putting Koda 6.1s in the WRX, but size issues have created problems for me. Enough problems that I no longer want to try and get them in. I read a link from here in regards to the CDT "Classic Series" 6.5" Components, So I picked those up from for $149.99, what a steal! In my buying spree I also picked up an extra set of CDT Tweeters with an attenuator to help and bring the sound stage up higher.

So this weekend I will create my amp board, run my new 0/1 guage power wire, and place the CDT Components in the front stock location.

One question is, where is a good place to put the second set of CDT Tweeters? I've listented to tweeters on the A-pilar of cars before and they always seem to shrill and bit, sounding a bit bright.


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