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Comment by gcbirzan | Hacker News Reader

> The cable harness used today is one of the three heaviest subsystems in the vehicle (weighing up to 60 kg)3. Traditional Ethernet cables use four differential pairs for data transmission, adding weight and routing complexity, which is not optimal for automotive applications. To address this, new IEEE standards were developed to support Ethernet transmission over single twisted pair cables, which, coupled with the reduced cable harness lengths enabled by zonal architecture, can offer significant cable savings and weight reduction.

Because in cars that are at least 1000kg, a few grams definitely matter.

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Actually the weight savings is irrelevant. The advantage is in the simplification of the cable assemblies! Did you know that just about every cable assembly in every car is made by hand‽ Hackaday wrote an article all about it:

https://hackaday.com/2022/07/27/the-surprisingly-manual-proc...

By having just one wire to transmit data and power to components in each zone it will be a significant cost savings. It also makes the various automotive engineer's jobs a lot easier.

So that makes me a bit concerned. This a single conduit with collision detection. All fine and good.

So does that mean every PCB and subassembly/controller in a car will be daisy-chained? Would one single broken wire disable the entire car or just the downstream modules? Do you create a "backbone" down the length of the car and fan the signal out like a nervous system?

It won't be that everything in the car is connected on one bus. What is more likely is that you have a zonal ECU that controls a group of a few sensors and actuators. That zonal ECU will likely be connected to other parts of the vehicle through more traditional Ethernet. The 10BASE-T1S standard requires that it can support a minimum of 8 nodes on the bus although you can support more but you aren't going to be hooking up absolutely everything together on it.

>Would one single broken wire disable the entire car

Not in this case but try shorting the two CAN bus wires together in an older vehicle.

There is a TON of work in designing, routing, manufacturing and installing harnesses which I think is more important than the mass savings. Harnesses really complicates design and assembly, because you have harnesses that pass through multiple parts and subassemblies managed by different teams.

The multidrop feature of this standard means that in a car, you could have a main harness that rarely needs any updates, and as features are added to the next model of car, most updates could be handled with a local wire harness update.

A harness mistake(s) cost Airbus billions on the A380 program.[1]

[1]https://www.nytimes.com/2006/12/11/business/worldbusiness/11...

You'd be surprised how much the reduced cable cost matters to an OEM.

Yes, I'd be surprised. How much money would reducing the number of pairs in a cable from 4 to 1 save? A few dollars, at most.

Save a few dollars, times 10's of thousands of vehicles in higher production models.

I've posted this before in more detail, but the short version is that when I was working at Ford Motor Co in the late 90's I remember seeing some internal documents championing how they saved ~$200 off a production Taurus (at the time a ~$20,000 vehicle) via a bunch of $10 and $20 individual cost savings. It was a big deal, added up to real dollars.

Yes, but this is a few dollars (and that's optimistic), PER CAR. That, and you'd need to invest a lot in changing the whole way you do networking.

There are benefits weight and cost and system complexity and network specifications, etc. There are certain things you just cannot do with CAN bus that manufacturers want to do. Using traditional Ethernet is possible (and I've done it), but the second you bring it up to penny pinchers they get a headache and the conversation is over. Having something like this allows you to make the transition while not just increasing capabilities, but actually decreasing costs.

There is more cost savings than you might think in a simplified wiring harness. Some 3rd party organization builds the harness, then it ships to the manufacturer, where it is usually installed by humans.

Besides the material savings of less actual wire, you most likely have labor savings on the harness build, and possibly on the installation if the new harness is easier to install based on the reduced overall weight and complexity.

The networking methodology side would likely not be overly complex. We already have CANbus device networks, and the associated software stacks. Changing to an ethernet based approach is a well-understood transition that would not require major changes, at least not beyond the incremental updates and other things that the engineers are already likely to be working on.

It's all margin and manfacturers optimise far smaller costs than that; when you're a VW or Toyota making 10MM cars a year it all adds up.

So, you're telling me, the manufacturers would've switched to this new amazing way of doing networking in the car, but it would've cost them an extra dollar and added a few hundred grams to the weight of the car, so they just had to wait for this standard to come along?

10/100BASE-T1 and its relatives are a long time coming. Car manufacturers are actively making these standards, they aren't "waiting for it to come around".

Exactly. A few dollars is an enormous price saving the automotive industry.

I've said it in another reply, but the automotive industry would've switched to this amazing new standard, except it would've added a couple of dollars to the cost and a few hundred grams to the weight of the car, so they just had to wait for this?

10BASE-T1S is more of alternative/replacement/upgrade to CAN and CAN FD, which use a single wire pair as bus, too. And automotive 100 MBit/s and 1 GBit/s Ethernet are also single-pair. (But they are point-to-point and therefore more expensive, as the article explains.)

And if it was only in one place, yea, maybe not worthwhile. But what happens if you save $5 each on 300 different systems in a production run of a million cars?

But you don't save 5 dollars on 300 systems, you save less, per car. The price and weight of the cables has very little to do with the decision to use this vs other ethernet standards.

Even if you assume replacement parts are marked up 5-10x over cost, wiring harnesses are expensive. Here's the one for my car: https://www.hondapartsonline.net/v-2012-honda-fit--base--1-5...

Dollars? You know that automotive calculate in 1/10 of cents. Every cable needs an appropriate connector. Every wire needs its dedicated pin in the connector. Did you know, that the connector housing is directly molded into the case because its cheaper?

Alone Ford at one point sold over 6.6 million vehicles a year.

Automotive manufacturers will spend 6 figures in NRE costs to save $0.003 in unit costs. If they only redesign every few model years, use the same hardware across several models, and they sell millions of cars per year, the math works out pretty well.

any change which can take $0.0001 or more off of the price of a part is pursued.

That only works if the replacement chips for the new interface don't cost even more

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