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Planning Mercedes S123 (station wagon) conversion

2217 Views 6 Replies 3 Participants Last post by  MoonUnit
Hello everyone,

I've been considering a conversion for quite a while now, finally thought to give a more thorough planning a "go"...
Object of desire is a Mercedes 123 station wagon from the mid 80s (these cars have a classic transmission layout, engine in the front, rear wheel-drive)

My mechanical skills I'd consider above average, have been into restoring classic cars for quite a while.

Been lurking around in this forum for many days now, but still more questions than answers.

I like the idea of getting rid of the whole drive train and replace it with a Tesla motor in the rear.
The 123 station wagon have no classic spare wheel well (spare wheel is stored at the side/inside the trunk), so the underbody in the rear is flat, should make fitting the electric motor easier.

I'm not particularly performance-orientated, yet the most powerful engine in these cars back then had 185 horsepower, I'd like to end up somewhere in that region.

Desired minimum range is 100 km.
Budget-wise I hope to stay below 20 k€ for the components.

Have not yet thought about batteries in detail...

I have not purchased a car yet, as my workshop is currently blocked with another project which I hopefully will finish soon.
But I wanted to start planning / buying some components in the meantime.

Biggest concern at the moment is getting the conversion street-legal. I am aware of the regulations in Germany, especially EMC and therefore the need of an "understanding" technical inspector. Have already asked the local TÜV Süd here (technical Inspection organisation) but they said they are not capable of doing this...

Anyone has an adress / contact of a TÜV prefferably in South Germany (Baden Württemberg)?

I want to get this topic straight before spending money....

Thanks, Stefan
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Hi Markus,

thanks for the info, but Siegen is approx. 500 km away from my location. Getting the car there by trailer after the build wouldn't be an issue, but I assume that I will have to discuss more than once with the engineer during the build, given it's my first conversion and no experience.
So a TÜV location within 1 hrs drive would be good (anywhere south of Stuttgart)...
Maybe some others might have a tip...
I can't help you with the TuV but I am interested to hear how you get on with the S123. Here in the UK, it's hard to find a good one at a decent price - they are all either rotten or restored and expensive. Decent ones may be cheaper in Germany, but remember they have hydraulic rear suspension that is powered from the engine so you'll need to factor in a hydraulic pump in your build. I am not sure but you may be able to convert the rear suspension to normal shocks and coils - I don't think this is possible for the later S124.

These guys (in Holland) have experience with drive trains the TUV can accept:

Anyway I want to get rid of the whole original drivetrain and fit in a Tesla rear SDU. I am aiming towards the Open Inverter solution for the inverter, not sure if I should wait for the Model 3 Open Inverter board or go with a Model S/X rear SDU. Any benefits/advantages of the Model 3 SDU over the Model S/X rear SDU?
I'm very envious of your friend and his barn full of old Mercs, I have a soft spot for them. I'm afraid I can't comment on the Tesla drive units as I haven't used one myself. I'm fitting a Hyper 9 to a Beetle, currently, which is hard enough without having to deal with all the alterations to the chassis that come with fitting a Tesla unit.

Good luck though, I'd love to see the finished outcome.
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