[WIP] Dual motor W124 E320 Estate

[RobCote]

Hi all

I'm not sure [WIP] is the proper tag at this point, but it's the closest available. I still feel like I'm in the planning stages, but I could use a bit of help already. That's probably a sign but I'm going to willfully ignore it and push on. What I really want to build is a Tesla dual motor conversion. I've been trying to plan out a build specifically for drag and drive events for a while now, and just saw that P.S.Mangelsdorf beat me to it. Big congrats to them for finishing Drag Week this year.

I intend to pick up a ~complete-ish Model S dual motor and harvest its running gear. I wanted to run this plan by you guys, though, because I've got a few questions. What I'm thinking of doing is of course installing both motors - likely SDU in the front and LDU in the rear just because that's the original configuration, but we'll see once the hardware is all together, what fits where. I would like to try to use the Model S battery as well since I'll have it and it should be the simplest to integrate (electrically speaking), but this will largely depend on the shape and size of things. I've also considered splitting it up into a front pack and a rear pack if I can't fit it in the main floor. I'm looking at a model year 2016+ Model S because the chargers had a higher capacity. Thanks to this forum for that info. I'm in Florida, so air conditioning is also a must. That's all I really want to carry over from the Model S to the E320. Anything else is low-priority "maybe someday" projects that will never happen.

My biggest question is would this truly require an - or rather two - OpenInverter boards? I think it depends on the extent of the swap, right? If I were to put all of the Tesla control systems in, it should work because it won't "know" it's riding in an old chassis. But do we know the lower limit of what hardware is needed to run on the OE control boards? I assume the entire CAN-BUS system would need to be online, but I'm not certain. Assuming I do need OI boards, I'd also need a vehicle control unit to make them play together, correct? Something like Zombieverter, but are there any other options?

Anyways, that's just a preliminary list of questions to help ensure I plan and shop correctly. I haven't had much luck finding any info on completed dual-motor swaps. There's one shop down here in FL that's done it in a C10, but that's running on Holley controls, I believe. And I think there's one or two others that were also professional builds. What I'd really like to do is document this so it's a bit more accessible to people who know as little as I do. The intent is equal parts going fast and learning EVs because I ain' never done this before. If you made it that far, here are a couple pictures of the chassis for this conversion. It's pretty clapped, but the structure is solid and it was dirt cheap. A truly rust free CA car. It's already rustled a lot of jimmies on the Mercedes forum where I've written my intent. Apparently, according to them, if it doesn't have that MB stamp on it, it cannot possibly work.

[johu]

Lovely, used to have one of these, just never made friends with the ridiculous fuel consumption.

Porting an entire modern car system into another vehicle is considered a pain in the A-pillar. Rolling with the OI boards can be as simple as connecting the same throttle signal to both for permanent 4WD. Maybe RWD/FWD selection by means of the switch that removed the forward/reverse signal from one drive unit.
For anything more elaborate a VCU is more practical I'd think

[janosch]

...
My biggest question is would this truly require an - or rather two - OpenInverter boards? I think it depends on the extent of the swap, right? If I were to put all of the Tesla control systems in, it should work because it won't "know" it's riding in an old chassis. But do we know the lower limit of what hardware is needed to run on the OE control boards? I assume the entire CAN-BUS system would need to be online, but I'm not certain. Assuming I do need OI boards, I'd also need a vehicle control unit to make them play together, correct? Something like Zombieverter, but are there any other options?
...

OpenInverter isn't the only solution, but porting the whole system is not a good idea, I have done it on a prototype and regretted it. I know other people who have done it and regretted it. This was for the Leaf/eNV200 system, so Tesla might be different.

Things that will cause needless pain:

• power steering
• speedo
• windshield wipers
• ABS

The brain of a Nissan checks if all these systems are present, and is unhappy if it doesn't find one, so either you have to figure out all their discrete signals as well as CAN messages and fake it in great detail - or bite the bullet and have the system hidden away under the bonnet somewhere even if it is not connected to anything else. If it is not connected to anything else it might report errors, then still immobilising your car.

Strongly advise against this approach. I also imagined car systems would be like an onion where you take layers off until you are happy. It is more like an egg, you got to smash it up and rebuild from first principles and you will have a much better time.

P.S: I used to have a W123, great project you have there!

[RobCote]

That's about what I expected would be the case. As neat as it would be to completely modernize this old clunker, it's not what I'm interested in doing right now. Porting over every feature can be a project for someone else. I just wanna go fast.

In that case, am I correct in understanding that OI would be a good solution? I.e. - 2 boards (one for each drive unit) plus a VCU.

[RobCote]

Lovely, used to have one of these, just never made friends with the ridiculous fuel consumption.

Porting an entire modern car system into another vehicle is considered a pain in the A-pillar. Rolling with the OI boards can be as simple as connecting the same throttle signal to both for permanent 4WD. Maybe RWD/FWD selection by means of the switch that removed the forward/reverse signal from one drive unit.
For anything more elaborate a VCU is more practical I'd think

Not sure how I missed this initially. Thanks for the info, that's super helpful. I'd like to keep it simple, because I know it'll be a challenge irregardlessly. RWD (or FWD) with selectable AWD by means of a switch isn't above my pay grade. That's a great solution.

Again, I love the idea of someone else doing a full swap including all the subsystems. Maybe someday I'll attempt it, but first let's get up and running.

[RobCote]

I've finally got a Tesla donor from which to harvest parts. It's a 2018 Model S 75D. So I believe this is a better charger (but maybe not their absolute highest capacity?) than earlier years. Is that correct?



I'd like youz guyzes input on everything I should retain from the car. My main objectives are to be able to drive it with both motors, so obviously the drive units are required, as well as the HV battery pack. I also want to keep the charger to be able to charge it. I'll hang onto all the HV cabling as well. I'll keep the battery cooling system components. But what else am I missing? Will I need control unit(s), or can OI handle battery cooling and charging all on its own? Any recommendations on what to keep is greatly appreciated!

[crasbe]

You should consider removing all or most the wiring loom. Not only for the connectors, but you're gonna need cables for the wiring of everything. And with the original wiring loom, you already have automotive grade cables, for free! In many different colors.