TipsyMcStagger

iTrader: (1)

The battery in my E36/LS2 swap is in the trunk (yes, I've been working on this swap for years). There is a power distribution point under the hood. I'm going to make new battery cables.

(Option 1) I can run one cable from the distribution point directly to the starter and a separate cable from the distribution point directly to the alternator.

(Option 2) Or, I can run one cable from the distribution point directly to the starter and a separate cable from the starter to the alternator. The two cables would be piggy-backed on the starter lug.

Option 2 would be make for cleaner routing but I'm wondering if it's detrimental from an operational standpoint vs. Option 1?

EDIT: Just thought of another question; Regardless of whether I end up with Option 1 or Option 2, what should I do about fusible links? Where should it (they?) be placed and what sizing is recommended?

TIA.

Crude sketches below:

Option 1


Option 2

Project GatTagO

iTrader: (7)

How did did BMW do it? Do that? If unsure, I would do #2.

Andrew

TipsyMcStagger

iTrader: (1)

From what I can see in the ETK (BMW electrical manual) the alternator is connected directly to the starter. This would mimic what I suggest in Option 2 in my first post.

I do have the battery cables that were original to the 2006 GTO from which this engine was pulled. In that setup, there are two cables that are crimped together at the positive battery lug. One goes to the starter and the other to the alternator. This is effectively what I describe as Option 1 above.

I guess either way is viable. I just wasn't sure if one was preferable to the other.

I'm still not certain about the fusible link situation.

Tipsy

Pop N Wood

iTrader: (1)

It really doesn't matter. I would be tempted to connect the alternator to the distribution point, that way all of your connectors are in one spot and you won't ever need to mess around with a connection buried at the starter.

It is not a bad idea to have a fuse and/or fusible link coming off the alternator. I run an 85 amp fuse with my 85 amp alternator (carb, low amps). You can get some nice high amp fuse holders from places that sell car stereo stuff. Fusible links work but they also suck, go with a fuse.

A starter can draw a couple hundred amps so not much future in trying to fuse that.

Having a distribution point is a nice way to do it.

Michael Yount

iTrader: (1)

I'd use option 1. When that starter load is released (engine starts, and you release the key to the "run" position) there's a pretty big voltage "bounce" that occurs as that big amp load drops out of the circuit. That swing can cause some interesting side effects to anything connected 'downstream' of the starter. I had my trunk mounted battery hot cable run to the starter, and then distributed power to everything else from there. When the starter would drop out upon start up, the swing was so big that it would drop below 6V for long enough to kill the time and presets on my stereo every time I started the car. Scratched my head for a while trying to figure that one out. Of course it bounces back "up" past 12V too...all of this occurs in a fraction of a second. But for me, it was long enough.

Not suggesting it would absolutely upset things at the alt --- just know that if I can isolate big loads from other loads, I try to do that. In fact, when I re-did the wiring for the Ford-to-LS swap, I ran a dedicated cable to the starter directly from the battery -- and provided 12V to everything else with completely separate circuits.

fieroguru

iTrader: (1)

My swap is wired up like option 2. Battery in front, engine in back, power cable goes to starter, then 2nd wire jumps from starter to alternator. Been that way close to 5 years and 45K miles and never had any issues.

The LS4 came with a 200A fusible links in the wire between the battery and alternator, so I used the same OEM cable and kept the fusible link (mine is positioned close to the alternator).

If you have to add one, you could also use a megafuse.
https://www.delcity.net/store/MEGA-F...caAnmDEALw_wcB

DT69cam

Option #1.

TipsyMcStagger

iTrader: (1)

Thanks for all of the feedback.

I'd prefer Option 2 from a tidiness perspective but I think I'll go with Option 1 to err on the conservative side.

Tipsy

DT69cam

Check out Madelectrical.com The owners name is Mark, to say he is knowledgeable in an understatement. You will not be able to get him off the phone. He has a diagram you should look at.

TipsyMcStagger

iTrader: (1)

Thanks. I'll have a look.

Tipsy