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Discussion Starter #21
I owned a w220 mercedes several years ago in the UK. It was an S280; 2.8l, 204 hp & 199 lbs-ft torque at 3000 rpm. It felt really quick, even though it was a just a 2.8l (maybe I'm easily thrilled..)
If the Chevy Bolt motor puts out 200 hp, with 266 lbs-ft torque from 0 rpm, it should power the old S-class nicely shouldn't it?
 

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It's still looks higher from the axle centerline, though
The Bolt (and Spark EV, and a few others) use a hollow-shaft motor so the motor is coaxial with the axles; as a result, the top of the motor and transaxle assembly is above the axle centreline by the radius of the motor case. The Tesla units (other than the taller Model S front unit) have the motor axis parallel to the axles and at about the same height, so again the top of the motor and transaxle assembly is above the axle centreline by the radius of the motor case... which is about the same between the Teslas and the Bolt.
 

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Don't worry about torque, worry about what will fit. Even the lowly Leaf motor would outrun half of the stock engines to 60mph.

The W220 has an independent rear suspension, so your play is to modify that to accept a motor with an integrated gearbox. Then you either fab the axles stubs together or have custom ones made.

The hard part is cutting the subframe, positioning the motor, and fabricating mounts without destroying the suspension geometry. Depending on the dimensions of the subframe, the difficulty may swing wildly between Tesla, Bolt, and Leaf motors.

I don't think anyone has a controller for the Bolt motor yet, but I haven't checked in a while, and it's only a matter of time. That's something to think about, though.

What's your plan for the OEM computers freaking out about the engine not being there anymore...?
 

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Discussion Starter #24
The work involved in fitting the motor in place of the rear differential sounds daunting. Cutting metal & fabrication isn't anything I've done, but I'd go for it if there are instructions out here on this forum.
Great question about the OEM computers freaking out.. I posed the same question here last year, but got no answer. Of note, Damien has put a gs450h motor in a 2001-2008 BMW 7 series. That model is loaded with integrated electronics which he was somehow able to by-pass or fool into thinking the ICE was still there. The crucial bits I'd need to function would be the ABS brakes & central locking. The speedo, motor temp & current etc are relatively easy to sort out I think.
 

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The fab is tough for sure, but if you want to keep the rear differential, your options are pretty much the Leaf or a cylinder motor (which will deliver less power for more money). Dual inline motors is an option for more torque. You might be able to mate the output of one side of a Bolt motor to a driveshaft U-joint...but you'd have to weld the other side and put the motor in sideways...just seems a bit weird. I've never seen it done.

I wonder if it would be easier to fuse a Tesla subframe with the Benz subframe...I'm off in the weeds.

I wish more OEM motors had flat faces and detachable gearboxes.
 

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Discussion Starter #26
You guys have really got me interested in putting a transaxle in place of the rear differential. It's the best setup I think, if I can wing it. The Bolt and Leaf motors have a pretty "small form factor" compared to my previous preference - the Lexus GS450H. Surely I can put one of them between the independent rear legs of the w220...
 

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... You might be able to mate the output of one side of a Bolt motor to a driveshaft U-joint...but you'd have to weld the other side and put the motor in sideways...
You can weld the diff solid or (much better) replace it with a spool, but you can't just lock one side stationary because that will spin the diff pinion gears rapidly and they are not intended to do that continuously.

Even with a spool, the remaining problem is that you still have the roughly 7:1 reduction gearing of the Bolt transaxle in addition to the car's original final drive reduction. That means the Bolt motor will hit its maximum speed at a low road speed. This is the same problem as faced by people attempting to use an EV drive unit (typically from a Tesla) to drive both axles of a 4X4.
 

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You guys have really got me interested in putting a transaxle in place of the rear differential. It's the best setup I think, if I can wing it. The Bolt and Leaf motors have a pretty "small form factor" compared to my previous preference - the Lexus GS450H. Surely I can put one of them between the independent rear legs of the w220...
The best part about a modern Mercedes, diyelectriccar vise, would be that you can drop the subframe, or even buy an extra, and work on that before even dismantling the donor car.
Fairly cheap to buy a used one:

If dropping your own, fill up the available space with construction foam first, then you see how much space you have, so you know if you'll need to modify the trunk floor.
Controller should fit in the tunnel, as it normally carries both exhaust and drive shaft. Battery pack can be split between petrol tank space and bottom of engine compartment, leaving a large front trunk for you :)

Not sure where a W220 spare wheel sits, but my S210 (E-class wagon. Funny how S is wagon and W is sedan for Mercedes) had it in the trunk, behind the left wheel well. Completely hidden. 205x55-R16. Mind well and truly boggled when I found that. That's also a LOT of battery space if you can utilize it.

If Norwegian laws were not so draconian, I would have done this already. But we can pretty much only rebuild cars older than 1972, because anything newer than that has to satisfy a lot of safety requirements which is outside the scope of DIY. Unfortunately this means no cars with rear subframes (I believe both BMW and Mercedes started using subframes in 1972, allthough I'm not 100% sure on the BMW part).
 

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W220 is one of those where the spare wheel is under trunk behind diff and fuel tank is above diff just behind the seats, isn't it?
I guess that's the usual sedan buildup from Mercedes, while the wagons have fuel tank under trunk, behind diff and spare wheel inside trunk, hidden in the wall behind wheel well.

Youcanfitsomanybatteriesinthisbadboy.png ;-)
 

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Discussion Starter #31
W220 is one of those where the spare wheel is under trunk behind diff and fuel tank is above diff just behind the seats, isn't it?
I guess that's the usual sedan buildup from Mercedes, while the wagons have fuel tank under trunk, behind diff and spare wheel inside trunk, hidden in the wall behind wheel well.

Youcanfitsomanybatteriesinthisbadboy.png ;-)
You're quite right about the location of the spare wheel in the W220. Really good insight into utilising the Mercedes rear subframe! Thanks so much for this. I've looked at images of the Tesla SDU in it's own subframe and compared them with images of the w220 subframe. I really think I can do this. Thankfully, there are readily available hacks to control the Tesla SDU.
 

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If dropping your own, fill up the available space with construction foam first, then you see how much space you have, so you know if you'll need to modify the trunk floor.
That is a hot tip...I used a ruler, paper, and a ton of measurements...
 
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