KahnBB6

iTrader: (5)

Okay, I’m genuinely stumped on this one.

For various reasons I have decided to upgrade my SC300’s alternator to a higher output aftermarket unit.

I don’t really have a crazy setup:

—No exotic aftermarket sound system

—Only one Denso TT fuel pump (19 amps max)

—just a couple of electric fans in addition to the big mechanical fan

-aftermarket plug and play HID headlight upgrade

—No battery relocation


This is upgrade is mostly to provide more amps at idle using modern 6-phase technology. I don’t really need 180 amps but I do need more than idle amperage my OEM Supra TT Auto 100 amp alternator gives.

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I went with a DC Power 180 amp alternator but have yet to install it because the “Big Three” main charging system cables have to be upgraded first.

It is recommended with this alternator that the Big Three be done using 2/0 size cables. Okay.... that’s rather huge but I took my measurements and ordered a full set with 5/16” eyelets for the alternator and chassis ground and 3/8” eyelets for the everything else.

And my plan is to install these alongside my OEM alternator cable, OEM engine block ground cable and my OEM battery negative to chassis connection.
...

My problem is that these things are *absolutely enormous and unwieldily* to attempt to install once I reach the battery terminals themselves.

I have a marine negative terminal with a taller than stock post to take the addition of two of these really thick cables.

But.... right up against the factory engine bay fuse box they are just too big and difficult to flex into any reasonably good spot to make them fit decently.

...

So I’m asking... for those of you with upgraded aftermarket high output alternators on your SC300 or SC400:

—Are you using 2/0 gauge (“Two-Aught”) Big Three cables? If so, can you describe or show how on Earth you fit them?

—Do you use another smaller gauge for the Big Three and if so what gauge did you go with?

—Is the 2/0 I am trying to use totally overkill? I want to do this right and correctly but I just find it hard to believe that this huge cable size is needed just for having upgraded my alternator.

I know I absolutely need to do a Big Three upgrade and thick cables are a part of that but do they need to be THIS massive in every case?

Thank you all. I appreciate any advice someone may have. I’m used to wiring jobs but not using electrical cables made for Superman’s daily workout.

What I have:



Comparison of different wire gauges, starting from an already large 4 gauge:

lexforlife

iTrader: (7)

Okay my friend

I use the bjg 3 as well . I use 2 gauge high end welding cable as its not obnoxiously huge and has a great bend radius capability . I have 2 grounds off alternator to body . New cable from alternator to fuse box . I also changed alt fusible link from 120amp to 150 Amp from early model sc400 as its a direct swap . I changed starter cable to 2 gauge as well . You will need to make one of your end connection for fuse box a 90 deg to fit correctly .

now my battery is in the trunk and with my 170amp custom upgraded mechman alt I get 14.5 volts running ,my alt puts out 139amps at idle . I run power house racing twin spal fan setup and with them on high , both big 450walbros on , my 1000watt stereo on with 12 inch sub hitting , ac on and hid's on , my voltage remains right around 14 volts hot .

I also added ground from head to block , 2 from block to body and 1 from head to firewall and have 2 grounds off battery to body .

t2d2

iTrader: (8)

I second the welding cable recommendation. It's pretty flexible, even at the thicker sizes.

KahnBB6

iTrader: (5)

Lexforlife, thank you!! So in your opinion 2 Gauge welding cable was sufficient for these upgrades? You definitely went above and beyond with the starter cable and extra grounds.

t2d2, the much thicker 2/0 (Two-Aught) cable I have is using quality welding wire and it is surprisingly flexible.... to a point.

I am certain that smaller (but still bug compared to the stock wiring) 2-Gauge cables can be made to fit into the tight factory battery area confines much more easily.

That’s really my issue: the thickness of 2/0, despite my getting it from quality welding wire, is nearly impossible to cram between the factory battery and fuse box.

If it’s totally overkill and if I can *safely* drop down to 2-Gauge or even 1-Gauge (also sourced from welding wire) then I know I can make it all fit with those smaller diameters fit in there.

I wasn’t aware we had a factory 150A Alternator fusible link option available from early SC400’s. I’ll get one of those pronto!

If I must work with 2/0 size to be totally safe then I’ll find a way to. It just seems very overkill for my build’s power demands.

t2d2

iTrader: (8)

Well, if you're already using welding wire, that's as good as it gets for flexibility... I'd have to think 2/0 is overkill, like your hunch. Pretty sure I used 2 ga for amps and winches; can't imagine that wouldn't be sufficient for grounding. You can always run multiple smaller wires, but connecting them all the same ring terminal gets more difficult. They would at least be much more flexible, and can be stacked to fit through a tighter space.

estSC

They probably gave you 2/0 because its the usually recommended gauge for 200 A. 2 AWG is about 125 A (although depending on conditions max amp rating is usually about 190 A). But since its inside the engine compartment and probably bundled with other wires there is less cooling and more engine bay heat, thats way the recommended amps is about 125 for 2 gauge.

The fans are intermittent, the fuel pump adds maybe 10 amps over the stock. 2 gauge will be fine in my opinion. But as I saw in your build thread you have emailed DC-power. It will be interesting to see what they will say.

KahnBB6

iTrader: (5)

Thanks guys! I also am of the mind that perhaps 2-Gauge or 1-Gauge might actually be fine for this but I am not experienced with these kinds of electrical charging and grounding upgrades so I defer to the experts and more experienced.

Many Supra owners only upgrade to 4-Gauge when they install Tundra 6-phase segmented 130 Amp alternators which the modify to fit but that may have to do with the much milder nature of that DIY only increasing total amperage from 100A to 130A. They may go with larger big three cables when using the Sequoia or Tundra 150 Amp 6-phase segmented alternator instead since that's a much bigger jump from the 100 Amp factory JZ alternators.

I found it interesting to try determining the size cable needed for given voltage, max amperage and lengths using this online calculator:
https://www.wirebarn.com/Wire-Calculator-_ep_41.html

However estSC you bring up a good point about the engine bay heat being a factor not just for the alternator and its voltage regulator but also the for cable itself.

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I did get a response back from DC Power yesterday and they did give me a little leeway but only to go down to 0-Gauge aka 1/0 size. Since I have a full set of 2/0 cables already which only need to be modified a bit for the 200 Amp in-line fuse and holder and the battery negative to chassis connection I will keep them and try to make them work.

Here is the response they sent me via email including an answer to my question about why their alternator connector adaptor only uses two wires when the SC and Supra alternator plug has three wires:

With the manufacturer of the alternator suggesting a minimum of 0-Gauge aka 1/0 I'm satisfied to use what I already have which, if I can make it all fit cleanly, is more than sufficient for safety. For all the trouble and expense of making all new 1/0 cables to drop down one size I would not be getting much more compact diameter to work with.

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The cable lengths I measured out and ordered are:

Alternator positive to battery: 9ft, 6in (still needs to be severed near the battery once mostly installed to add new connectors for the in-line 200 Amp ANL fuse connection)
Engine Block to Battery Negative: 4ft
Battery Negative to Factory Chassis Ground next to the washer fluid filler neck: 1ft, 6in (but I am going to shorten this considerably with a new connector crimped at the right of rotation to make it fit cleanly)

One thing I did was ask Driftmotion to add corrugated protective tubing to each cable. I am going to leave this intact but remove some of it the closer these 2/0 wires are to the battery. For the battery negative to chassis short wire I am removing it entirely and I am going to considerably shorten the length and create a new terminal end.

Some big cable cutters and a handheld hydraulic cable connector crimp tool will be needed next. It's so close to Christmas I probably won't get it all done until after.

I am also picking up a 1992-1994 SC400 style 150A ALT fusible link tomorrow which I will swap in to replace the factory 120A ALT fusible link. Though since I am not changing the factory alternator positive cable but merely adding on top of it direct to the battery with its own fuse this may be overkill.

t2d2

iTrader: (8)

I checked my winch stuff and it was 2 ga, as I remembered. (That's a rarity!) Looking back at amp draw-cable run charts, 4 ga is sufficient for 200A up to 6' and 2 ga up to 8', although that's the total system length, which means positive plus [negative] return; definitely complicates the math for an engine bay with varied paths. 180A extends the 2 ga distance to 10'.

KahnBB6

iTrader: (5)

In front...? Actually no. My fans are all behind the radiator. I currently have the OEM Supra 2JZ-GTE mechanical clutch fan and an OEM Supra auxiliary electric fan that sits to the side of the main mechanical fan within a factory Supra TT shroud. This is the factory stock cooling fan setup found on 1993-1996 Supra MKIV TT 6-speeds and it has worked quite well so far.

What I am getting ready to install is the 97-02 Supra TT fan shroud which allows for two of those OEM TT auxiliary electric fans in addition to the main mechanical cooling fan.

Aside, I am considering buying an additional Spal pusher style fan to go in front of the radiator to replicate the setup that Supra TT Automatics had just for additional A/C condenser cooling in hot weather. And I am only planning on the Spal fan because gathering all the parts for a stock Supra TT Auto condenser pusher fan are very hard to come by now.

I am also using a factory side mount all metal intercooler and factory piping for it from an early model Soarer JZZ30 which I had custom rebuilt by Bell Intercoolers with a modern and more efficient core that flows more CFM in excess of a factory original Supra TT sidemount IC. So there is no FMIC to get in the way of my radiator's cooling efficiency either.

joe diego

iTrader: (3)

I’m currently running a 1/0 gauge wire from the battery in the trunk to the original positive terminal in the engine bay.
I’m about to install an SC430 alternator and I guess upgrading to the big 3 is a must? 🤷🏻
So the 1/0 gauge wire from the battery goes straight to the alternator, correct? What am I supposed to do with the starter wire and engine bay fuse box wire? Do I run those two wires to the alternator as well?

KahnBB6

iTrader: (5)

I have only had a crash course learning about this all in the last couple of months so please bear with me. This reply post will be a bit of an information dump since I'm still figuring all of this out myself.

....

As far as wire gauge recommendations go I defer to the people with more experience or to the manufacturers. My setup's 2/0 gauge wire is what I went with because it was recommended to me.

First, here's a good wire length and size online calculator I found that has helped me: https://www.wirebarn.com/Wire-Calculator-_ep_41.html

1/0 gauge wire to a trunk mounted battery sounds to me like it's in the ballpark but I haven't tried doing a remote battery setup so I'm not sure. If you call Driftmotion and get Aaron on the phone he can advise as to the best recommendation for what size wires should be used in that kind of setup.

Make sure you get the 2003-2010 Lexus SC430 alternator. That's the 130 Amp version. P/N: 27060-50280-84. It was also used in the 2000-2003 LS430 apparently. Having the oval 3-pin connector built in is an advantage over the Tundra alternators. Other than having to shave the mounting ear a bit and remove the one that gets too close to the timing belt.

Yep, the Big Three upgrade is required with an upgraded alternator. You add the new cables to your existing factory ones. The higher output alternator just needs to have a larger "pipe" through which to flow current from the battery. And the ground points around the car need to have bigger "pipes" as well. So we have to upgrade them.

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The heavy gauge additional wire from the alternator's positive post needs to run the original path the factory alternator wire takes but it will not replace the factory fuse box wire. With a battery in the engine bay you run the end of that wire into an ANL fuse (in your case you would get a 150 Amp ANL fuse and holder) with 5/16th eyelet end connector at the end of the wire. Then you have a much shorter same gauge wire going from the ANL fuse to your battery. You can use the stock battery terminal connectors or get some aftermarket type-- whatever you choose.

For all these cables you need to use a wire with fine strands. Welding type wire is what everyone uses regardless of whether they do it themselves or have a shop or company build them a kit. The three main upgrade cables should all be the same gauge.

To crimp the cables and adjust the lengths (you will need to) you can use:

--TEMCo TH0007 hammer lug crimper
--a 3lb or so small steel mallet
--a pair of cable cutters rated for the cable size you're using
--for the connectors you can get them online or from a marine supply store (eyelets are available in 5/16ths and 3/8ths so pick them according to what general size terminal each connection will need).

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For the installation of the engine block additional ground wire that goes to the battery negative I HIGHLY recommend buying an inexpensive $100 or so video boroscope tool from Harbor Freight, Amazon, Summit Racing or any auto supply vendor you prefer. This will make eyeballing where the big cable eyelet, stock ground cable eyelet and bolt all line up into the block SO much easier. It's an extremely difficult job without one of those boroscope cameras. NO fancy features are needed-- just video.

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I contacted DC Power and asked about the cable size and their official recommendation was 1/0 (aka 0 Gauge) with the battery in the engine bay. I already had 2/0 gauge cables so I just used those. For a trunk mounted battery I think they might recommend larger wire of at least 2/0? I'm not sure honestly.

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I'll also address replacing the 120A ALT fusible link in the fuse box with the 150 Amp version from early SC400's: P/N 90982-08272. Some people do this and some do not.

There is a particular way it has to be removed which I saw a thread about the other day. I think this was recommended in the SupraForums thread because some people were actually replacing some of the charge and ground cables going to their factory fuse and relay box bus bars.

For what it's worth the DC Power folks said it was a fine idea but not necessary because when doing a standard add-on Big Three upgrade because the factory electrical system will not draw more amps than it was designed to. Gerrb even told me that he does not change the factory 120A ALT fusible link in his SC's with the Mechman 240 Amp alternators that he runs with upgraded "Big Three" cables.

I am going to install the 92-94 SC400 150 Amp fusible link anyway because it's a factory SC configuration part but if you think about it what they are saying does make sense: current (amps) are drawn, not pushed so the factory fuse and relay box will only draw the current it needs to. If you add additional circuits for more functions outside of that then those will have their own fuses and connections to the battery either individually or with an aftermarket fuse box with its own bus-bar and thus none of those additional circuits are going to affect the factory electrical system's current draw.

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Also I think with a trunk mounted battery setup, in addition to requiring a pretty big size set of cables, requires that you run an additional ground off the alternator to the chassis, another additional ground off the transmission to the chassis and probably a couple of other places as well.

Again, I am not the person to ask about how to do this properly with a trunk mounted battery and I defer to the experts :/

Driftmotion sells a pretty good kits in 2/0 though and I think Aaron does rate it for a trunk mounted battery setup with additional grounds beyond just a standard "Big Three" upgrade. You have to enter your ballpark length measurements and options you want for each cable when ordering.

t2d2

iTrader: (8)

"The three main upgrade cables should all be the same gauge."

I have to question the wisdom of that. Longer runs require thicker cable to support the same amps, so why would all the upgraded cables of different lengths have to be the same gauge?

AutoZone rents (loans) the video boroscopes. No need to buy one if it's for just the one job.

"I contacted DC Power and asked about the cable size and their official recommendation was 1/0 (aka 0 Gauge) with the battery in the engine bay."

I assume that's for 180A, not for 130A? 2 ga is plenty for 130A, in general.

"I am going to install the 92-94 SC400 150 Amp fusible link anyway because it's a factory SC configuration part but if you think about it what they are saying does make sense: current (amps) are drawn, not pushed so the factory fuse and relay box will only draw the current it needs to."

Following that logic, you should stick with the 120A fusible link unless you're adding more components to the fuse & relay boxes. Otherwise, you're raising the trip point needlessly and lowering the protection it's designed for. You want the fusible link to blow before anything downstream melts.

joe diego

iTrader: (3)

I hope you guys don’t mind me posting this here... It may help someone, like myself, with the Big 3.

I upgraded to a SC430 alternator and now I’m a little confused on how to wire it up to the three prong oval pigtail. (My SC is a 92 with round alternator plug). Could someone please tell me which tabs on the male side of the SC430 alternator are the “L, IG, S”?

I took a pic of the SC430 male side of the connector (back side of the SC430 alternator).


............

The original wires on my 92 SC going to the alternator are yellow/green, black/yellow, and white.

Y/G = L
B/Y = IG
W = S

KahnBB6

iTrader: (5)

I have been so busy I haven't had time to respond properly, sorry t2d2. I do agree with your logic there. All I know is that the 1992-1994 SC400 had the 150A ALT fuse in place with generally the same chassis wiring and those cars had 130 Amp 3-phase alternators from the factory for some reason. Still, I agree. I'll come back and reply to all the points soon.

Joe, you will need to pick up alternator connector: 90980-11349. I don't know the repair terminal wires for it offhand but if you search on SupraForums for that part number or give it to a Toyota or Lexus dealer they can match the right repair terminal wires for it if needed. It may be that the SC's older round style connector terminals cannot fit the oval type connector after being de-pinned but maybe they will? I'm not sure.

Here's a screenshot from the 1995 Supra MKIV electrical TSRM as those cars use the oval type connector as standard. Go by the pin numbers on the Supra/oval alternator connector rather than wire colors and match up the L, IG and S respectively.

lexforlife

iTrader: (7)

Hey guys alittle mis info here being displayed

wire thickness or gauge is Not More critical than strands of wire and quality of the strands , period . I use 2 gauged high end welding cable that has a higher strand count and higher end copper for better conductivity .been running this since 2013 without issue . My battery is in the trunk with 2 grounds off battery to different points in the trunk .i have since last year upgraded my alternator go a custom mechman 170amp version , not off the shelf with a fixed voltage of 14.8.

I can show any nay sayer via live video via my BTI can bus gauge my live running volts . After car has been running for a hour , cables heat up and provide resistance I still get 14.3- 14.5 volts at my battery in the trunk and I get 14.7 at alternator so my voltage drop is extremely minimal ..I have dual spa and running high speed and low speed , 2 big walbro , 1000 stereo system and bare min with all on with ac and hid lights is around 14.1 ish steady

I use the 150amp alt fuse for a little more headroom for Amp consumption as 120amp should be enough but who really adds up all that drawing power ,component by component so at 150 Amp I'm covered

so really comes down to quality of cable and more then ample grounds throughout