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Discussion Starter · #1 ·
I come from the world of ls powered vehicles, I’ve built 4 ls swapped miatas and 2 fd rx7s. My wife has a miata that is very special to her, it currently has a 525hp ls3 crate motor. The car is a blast to drive and has about a 200 mile range, runs 10s in the 1/4. I would like to swap it again, this time going with a Tesla swap, thinking of a model 3 drive unit replacing the rear end. That’s about as far as I have gotten on the idea, not really sure what to do for batteries, controllers and the rest. The hope is to sell the entire ls swap and fund the Tesla swap. I’ll be doing a lot of research trying to figure out how to make this work, I’m sure this form will be a huge help.
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My wife has a miata that is very special to her, it currently has a 525hp ls3 crate motor. The car is a blast to drive and has about a 200 mile range, runs 10s in the 1/4. I would like to swap it again, this time going with a Tesla swap...

The hope is to sell the entire ls swap and fund the Tesla swap.
This doesn't make sense to me. Why not sell the complete and working car (with LS3 powertrain) and convert another Miata, since none of the LS-specific parts will be used in the EV conversion? Re-converting a car means throwing away conversion effort, and it's hard to imagine anyone paying anywhere close to the value of the working LS-converted car for a pile of parts that you promise will work to do another conversion.
 

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I love Miatas too! I have a 320whp turbo one! I've thought about EV conversion too and also liked the idea of a transaxle motor assembly mounted where the rear diff is located in the Miata. I would get it mounted on the subframe whatever that would take and then start cutting away bodywork until it fit. I've seen several EV Miatas and they all kept the transmission, driveshaft, diff, etc and end up not having much room for batteries, but if you ditch all that stuff then there's lots more room.
 

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Discussion Starter · #4 ·
This doesn't make sense to me. Why not sell the complete and working car (with LS3 powertrain) and convert another Miata, since none of the LS-specific parts will be used in the EV conversion? Re-converting a car means throwing away conversion effort, and it's hard to imagine anyone paying anywhere close to the value of the working LS-converted car for a pile of parts that you promise will work to do another conversion.
Unfortunately my wife has emotional attachment to the car, it was left to her by her late mother. In the end it’s only money and I have plenty of time to make it happen.
 

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... this time going with a Tesla swap, thinking of a model 3 drive unit replacing the rear end.
That makes sense to me. The next step, in my opinion, would be to get some accurate drawings (or better, 3D model) of the Miata rear end and the Model 3 drive unit, and see if there is any hope of compatibility.

One likely problem is that the Model 3 motor sits ahead of the axle line. That is good for mass distribution, but there might not be enough space from the axle line to the back of the seats.

Some conversions use the entire subframe and suspension as well as the drive unit. That ensures that everything works together, but can be a fit problem... the NA Miata is only 1,675 mm (65.9 in) wide with 1427 mm (56.2 in) rear track, but the Model 3 bits are sized for a car which is 1,849 mm (72.8 in) wide with 1580 mm (62.2 in) rear track.

The only conversion that I have seen anything about which uses the Model 3 drive unit is the latest version of tiger82's Tesla Powered Cobra Race Car.

That’s about as far as I have gotten on the idea, not really sure what to do for batteries, controllers and the rest.
If the Model 3 drive unit fits in, that pretty well leaves the engine compartment as the only battery space.
 

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I've thought about EV conversion too and also liked the idea of a transaxle motor assembly mounted where the rear diff is located in the Miata. I would get it mounted on the subframe whatever that would take and then start cutting away bodywork until it fit.
That would take building a new subframe. Unfortunately the Miata rear suspension is relatively wide for a narrow car, leaving little room for the drive unit (the final drive is much smaller than an electric drive unit and just fits), so it's likely that the drive unit won't fit even with a completely custom subframe. The good thing about this car is that the fixed structure (unibody) in the rear is all well above the axle line, leaving a nice clear space to work with.
 

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Discussion Starter · #7 ·
That makes sense to me. The next step, in my opinion, would be to get some accurate drawings (or better, 3D model) of the Miata rear end and the Model 3 drive unit, and see if there is any hope of compatibility.

One likely problem is that the Model 3 motor sits ahead of the axle line. That is good for mass distribution, but there might not be enough space from the axle line to the back of the seats.

Some conversions use the entire subframe and suspension as well as the drive unit. That ensures that everything works together, but can be a fit problem... the NA Miata is only 1,675 mm (65.9 in) wide with 1427 mm (56.2 in) rear track, but the Model 3 bits are sized for a car which is 1,849 mm (72.8 in) wide with 1580 mm (62.2 in) rear track.

The only conversion that I have seen anything about which uses the Model 3 drive unit is the latest version of tiger82's Tesla Powered Cobra Race Car.


If the Model 3 drive unit fits in, that pretty well leaves the engine compartment as the only battery space.
I would most likely have to make the drive unit fit in the miata subframe, that’s what I did with the 8.8 in it now, used dss to make custom axles, engine bay would be the plan for batteries, I just don’t know what batteries I will use at the moment, maybe build my own out of a ton of 18650s.
 

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Unfortunately my wife has emotional attachment to the car, it was left to her by her late mother.
Ah... understandable. You might want to work out the whole EV conversion on another Miata (which doesn't need to have a great body or suspension), then swap all the bits into the special car; that could avoid having the car out of service for what could be a long time, and would let you make mistakes (or "design adjustments") on body parts that don't matter so much.
 

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I would most likely have to make the drive unit fit in the miata subframe, that’s what I did with the 8.8 in it now...
An EV drive unit is much wider than a final drive unit such as that Ford 8.8 IRS differential assembly.

By the way, you actually used a Ford final drive in an LS conversion? Interesting, and no reason it can't work fine, but GM components are more obvious with a GM engine and (presumably) a GM version of a transmission.

... I just don’t know what batteries I will use at the moment, maybe build my own out of a ton of 18650s.
That's likely an enormous waste of time, resulting in a pack inferior to any salvaged EV modules.
 

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Discussion Starter · #10 ·
An EV drive unit is much wider than a final drive unit such as that Ford 8.8 IRS differential assembly.

By the way, you actually used a Ford final drive in an LS conversion? Interesting, and no reason it can't work fine, but GM components are more obvious with a GM engine and (presumably) a GM version of a transmission.


That's likely an enormous waste of time, resulting in a pack inferior to any salvaged EV modules.
Width shouldn’t be an issue, there a ton of room under the car, after the gas tank is out I shouldn’t have any issues figuring out how to hang the thing, I have seen a c5 corvette transaxle mounted in the back of a miata.
The Ford unit is strong and has better gearing option and I know how to work on it over a getrag lol.
I’ll still explore battery options, if I could find a good deal on a wrecked model 3 then that would be my best bet.
 

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Width shouldn’t be an issue, there a ton of room under the car, after the gas tank is out I shouldn’t have any issues figuring out how to hang the thing, I have seen a c5 corvette transaxle mounted in the back of a miata.
The Model 3 drive unit is much wider than a C5 transaxle... but the C5 transaxle installation would be interesting to see, anyway, as it extends quite far forward to fit in a Miata (especially an NA/NB rather than the longer NC). I tried a web search, and I can see discussions of the possibility but no indication that anyone has ever done it, or that it was workable.

I’ll still explore battery options, if I could find a good deal on a wrecked model 3 then that would be my best bet.
The Model 3 battery will be useless in a Miata - the modules are far too long.
 

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This may be an answer. Tesla LDU split motor with Dana 60 flange for just about any u joint combo or make your own setup and bolt it to the flange. Drive shaft to your differential with a mid bearing with a slip yoke. Your rear end is already beefed up so you shouldn't grenade it. Red line about 5700 RPM. Availability may be an issue, it just came out today.


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