Best way to splice...

I need to splice a 20AWG wire (TXL? or larger from a Holley HP ECU to seven 22759/32-20 wires that lead to the grounds of the engine sensors. What is the best way to do this? I can split 1 into 3, via an inline butt splice, then again split into 3 from 1 (thermister grounds) and then 2 from 1 for the other 2 initial splices. (7 total) This all would happen just prior to 2 deutch connectors (1 for 3 and 1 for 4).

Or... I can do an open barrel splice with all 8 wires in the same splice, either 1 in and 7 out, or all 8 in one side and then a 180 degree bend coming out of the open barrel. All the options would be covered first by SCL then DR-25.

Thanks in advance.

Scott

PS I also will be splitting the 20 AWG Holley power wire into 4 22759/32-20 for the 4 sensors that require 5V power.

I personally always opt for the last option though I'd use a closed Versakrimp parallel splice rather than open barrel.

https://www.prowireusa.com/MLX-SPLICE-KIT

You don't need to buy the whole farm if you know your size - but at least this gives you an idea of sizing options.

Hey Scott,

This is definitely an issue we run into quite a bit.

All of the methods you've described are valid, and electrically there won't be much difference between them. Personally, I try to keep the number of splices to a minimum, so I'd lean towards a single splice with all 8 conductors entering from one side and the ECU wire folded back 180° into the splice.

For eight 20 AWG conductors you're looking at roughly 8,160 CMA, so I'd be looking for a splice sized somewhere around the 10-12 AWG range.

For larger multi-wire splices like this, I generally prefer a closed-barrel splice. I find it does a better job of capturing all the conductors and gives a more consistent crimp around the entire bundle.

Placement is important too. Aim to have the splice located in a section of the harness that will be secured and reasonably rigid, such as in the boot behind a connector or at a junction point. Covering it with SCL or a molded boot also provides some additional strain relief.

The same principle would apply to the 5V supply wiring as well. Sensor power and sensor ground circuits carry very little current, so consolidating them into a single appropriately sized splice is perfectly acceptable.

My preferred way to split single outputs, lets use the 5V reference for example, is to use a bussed Deutsch DT connector (I really wish they made a DTM version for this), and then run all of the 5V reference wires back to a spot near the ECU, into the DT connector.

This provides a few advantages. It is a clean way to splice several circuits, and with the variety of bussed options, you can tailor the connectors to the specific need.

This allows a way to disable the car easily, ad a bit of a theft deterrent, if you have the connector(s) somewhat easily accessible, by simply removing the bussed connector.

It provides a trouble shooing point where if you suspect a circuit has an issue, you can pull it easily out of the connector and isolate it from the rest of the circuits, and/or test for continuity on each circuit to the sensor or device it supplies or even to ground, if you suspect a short.

If you find that you need to add more circuits, no need to cut into the harness, just add another circuit pinning it into the connector, and if you run out of room in the existing connector, you can move up to the next pin count connector, or add another bussed connector.

There are other options, like Delphi has what they call "splice savers", that are more comb like, but definitely do the job as well.

That's definitely a valid approach and I can see the appeal, particularly from a future expansion and serviceability standpoint.

Personally though, I try to avoid adding connectors purely to avoid a single splice.

In reality, you're trading one crimped splice for multiple terminals, connector housings, and additional crimp joints. From a reliability standpoint, I'd generally have more confidence in a single well-executed splice than several additional connector terminals. Statistically, you're more likely to have an issue with one of those extra connector pins than a properly crimped splice. A single splice also tends to be cleaner and more compact than adding several larger connectors into the harness.

It also depends on how you implement it. For this particular example, you'd likely end up with a separate distribution connector for the 5V reference and another for the sensor grounds. That means adding two larger DT connectors, whereas my preference is to use a single DTM connector carrying spare sensor inputs, a 5V reference, and a sensor ground. A DTM12 will usually cover this quite well, and depending on how many spare inputs and outputs you have available, you can often include spare outputs in the same connector too. In my opinion, this achieves the same future-proofing and modularity benefits with less bulk, cost, and complexity.

For diagnostics, checking at the faulty sensor connector against a known good sensor connector will usually tell you pretty quickly whether the 5V or sensor ground is missing. From there you can narrow it down to the sensor branch, splice, or connector bus fairly easily.

At the end of the day both methods will work fine. I just tend to lean towards simplicity where possible and save the connectors for where they provide a real benefit.