Big 3 Upgrade: Replace factory wires?

[.killsec]

Hey guys,

I'm planning on doing the big 3 upgrade soon and looked everywhere for a guide to help me along but nothing specific for a Supra. I did see a few people on other car forums not specific to mkivs stating to absolutely not replace factory wiring but instead to add to it and I'm wondering why that is. I'd like to tidy up the wire loom in the process so the goal is not to add more in to the mix. Additionally I installed a 200amp alternator so I'd like to get the full potential out of it

The other guides I've read gave enough info to where I feel confident in my ability to take it on, but I just want some clarity on what possible reason if any at all there would be in not replacing stock wiring. Seems odd to me.

Any help would be greatly appreciated!

[Swampy442]

Whats a big 3 upgrade?

[Frank Bullitt]

Alternator to battery positive connection, battery negative to chassis connection & engine ground to chassis connection. Usually done when you are running a big sound system using 0 AWG cable.

[Noz]

Whats a big 3 upgrade?

https://jlaudio.zendesk.com/hc/en-us...Wiring-Upgrade

I had to google it as well

[.killsec]

Haha sorry, thought the name was more commonly known. My bad. So, does anyone see any reason why replacing the factory cables with upgraded ones would be a bad idea?

[Harrypm82]

Haha sorry, thought the name was more commonly known. My bad. So, does anyone see any reason why replacing the factory cables with upgraded ones would be a bad idea?

Unless you're gonna run a massive sound system with a big output alternator and about 3 batteries, there is no point.

[johnny g]

Unless you're gonna run a massive sound system with a big output alternator and about 3 batteries, there is no point.

Agreed, no need to do it unless you're running a higher output alternator. Get a good battery, and maybe a 0.5 Farad capacitor in the sub-amp wiring line. Job done.

[.killsec]

All great info guys thank you! I'm not planning on a massive sound system, just probably going to add a decent sub and some focals. I've got some other things planned down the way that'll draw some power as well. I might still go ahead and replace the power wires anyways just in an effort to clean up the engine bay by getting rid of ugly factory wiring. I'll just call it future proofing? I guess? lol.

[Harrypm82]

All great info guys thank you! I'm not planning on a massive sound system, just probably going to add a decent sub and some focals. I've got some other things planned down the way that'll draw some power as well. I might still go ahead and replace the power wires anyways just in an effort to clean up the engine bay by getting rid of ugly factory wiring. I'll just call it future proofing? I guess? lol.

Remember electrics don't draw the current, it uses what it's given

[.killsec]

On the same topic of power distro upgrading, from the postive post in it's stock config there are two power wires, one leading to the fuse box, the other to the starter solenoid. Does anyone have any idea where the junction is made to the alternator power wire? I've been looking in my engine bay for the last hour and I think I'm going a bit mad It just doesn't make much sense to me to NOT have the alternator directly tied to the battery. Going through the fuse box and then to the battery seems like an odd thing to do. I can't see much around the starter but it doesn't look like there is any sort of junction made there so my suspicion is on the fuse box. I was hoping someone could lead me in the right direction before I look further. So, am I missing something painfully obvious or are my assumptions correct about the alternator going through the fuse box first and then to battery? Any help would be greatly appreciated. I've been digging through manuals all day and googling for help to no avail.

Update: Turns out the alternator runs up to the fuse box. Not sure if this will help anyone but eh. Figured I would add it.