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Porsche 911 (996) Tesla Swap

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Hello Folks,

Next week, I will begin pulling the engine out of a 1999 Porsche 911 C4 so that I can start an EV conversion project. I've done multiple engine swaps and have a good basic understanding of circuits. Plus, I've been watching a good amount of YouTube, including some of Rich Rebuilds Mini Cooper conversion series, so I got that going for me.

I would like to use the Tesla Model 3 Rear Drive unit from the standard range car (will be ditching the awd system). My understanding is that the Model 3s use a new motor type with more efficiency. I believe it is referred to as a Internal Permanent Magnet-Synchronous Reluctance Motor. Anyway, I figure, the Model 3 Standard Range does 0-60 in about 5 seconds and weighs about 700 pounds more than what this should weigh when it's done, so the standard range motor should be enough power.

Question for anyone who might know: Is the rear drive unit in the Model 3 Standard Range, the same as what comes in the Long Range/ Performance model?

Battery Range: I would be happy with 40kWh here, I figure that would give me about ~140 mile range, and not add too much weight.

I'm cheap. I hope to do the entire swap for around $10k (this takes into account getting some money back from selling Porsche parts). This means I probably will be looking for something other than Tesla battery modules.

I got to speak with Michael Bream at EV West today, he brought up a good point that the Model 3 motor places the axles behind the electric motor, thus transferring some weight forward in the car, whereas the Model S and Model X motors place the electric motor behind the rear axle (like a 911 engine sits). I figure I will be adding battery pack weight to the back of the car so the Model 3 motor would be okay.

I have heard that the Model 3 motor is newer for swaps and so people are still working on motor controllers and things like this. I'm all ears to any advice or information you think would be helpful.

YouTube video of the car I'll be swapping and some initial thoughts:
Ebay Listing for Model 3 Motor: 2020 Tesla Model 3 Rear Drive Electric Drivetrain Engine Motor Unit | eBay

Picture of the 911 being swapped.
Wheel Tire Car Vehicle Hood

Thanks for reading this. This is a dream project of mine and has taken a while to even get to this point.
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Nice project. I'm excited for you.

I'm super keen to see show you go so I'll be following keenly. Budget of 10k seems ambitious from all my research but what do I know [emoji2371]

I'm converting a '77 Targa, planning on a Model S drive unit and OXDrive battery pack from eGT. Full kit from them is 5x your budget but I'm paying for their R&D.

Best of luck on the project mate

Sent from my SM-G998B using Tapatalk
 

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I would like to use the Tesla Model 3 Rear Drive unit from the standard range car (will be ditching the awd system). My understanding is that the Model 3s use a new motor type with more efficiency. I believe it is referred to as a Internal Permanent Magnet-Synchronous Reluctance Motor.
Yes, this is an internal permanent magnet (IPM) synchronous motor, and it is more efficient than an asynchronous (induction) motor. All IPM motors produce some of their torque from a reluctance effect; the Model 3 IPM motor certainly does, and is typical in this respect. This is only new to Tesla - the rest of the EV world has been using IPM motors for a decade.

Question for anyone who might know: Is the rear drive unit in the Model 3 Standard Range, the same as what comes in the Long Range/ Performance model?
I don't know, but since you're interested in the Model 3 rear motor you might want to watch Prof. John Kelly's Weber Auto video about this series of motors and drive units.

I got to speak with Michael Bream at EV West today, he brought up a good point that the Model 3 motor places the axles behind the electric motor, thus transferring some weight forward in the car, whereas the Model S and Model X motors place the electric motor behind the rear axle (like a 911 engine sits). I figure I will be adding battery pack weight to the back of the car so the Model 3 motor would be okay.
True, and I think the configuration with the motor ahead of the axle line is desirable, as long as it fits - the car was designed for only a relatively narrow transaxle ahead of the axle line. The 996 should be better for this fit than the older semi-trailing arm 911's.

I have heard that the Model 3 motor is newer for swaps and so people are still working on motor controllers and things like this. I'm all ears to any advice or information you think would be helpful.
The Model 3 is relatively new, so yes, it has only recently been used in swaps. Two of note, although they are not Porches and not even similar to a 911:
 

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Discussion Starter · #4 ·
Nice project. I'm excited for you.
I'm super keen to see show you go so I'll be following keenly. Budget of 10k seems ambitious from all my research but what do I know [emoji2371]
I'm converting a '77 Targa, planning on a Model S drive unit and OXDrive battery pack from eGT. Full kit from them is 5x your budget but I'm paying for their R&D.
Best of luck on the project mate
Hi Jaycee, thanks for the reply. Your project sounds like it will be quite the final product. I just looked up Electric GT, their products look really nice. Are you documenting any of the build?
 

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I hope so. I'm in deep, first project and blissfully ignorant of how easy it is to get dragged into doing "everything" ! So much fun though, so that's fine. It's documented on insta @porsche_9e11 [emoji6]

Sent from my SM-G998B using Tapatalk
 

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Discussion Starter · #6 ·
Yes, this is an internal permanent magnet (IPM) synchronous motor, and it is more efficient than an asynchronous (induction) motor. All IPM motors produce some of their torque from a reluctance effect; the Model 3 IPM motor certainly does, and is typical in this respect. This is only new to Tesla - the rest of the EV world has been using IPM motors for a decade.

I don't know, but since you're interested in the Model 3 rear motor you might want to watch Prof. John Kelly's Weber Auto video about this series of motors and drive units.

True, and I think the configuration with the motor ahead of the axle line is desirable, as long as it fits - the car was designed for only a relatively narrow transaxle ahead of the axle line. The 996 should be better for this fit than the older semi-trailing arm 911's.

The Model 3 is relatively new, so yes, it has only recently been used in swaps. Two of note, although they are not Porches and not even similar to a 911:
Brian, thank you for all of the info! I just watched Prof. John Kelley's video. It was excellent and now I think I have a pretty good idea on the difference between the Model 3 rear drive units, which is really only the inverter and maybe the stator. Yes, I would like to put the motor ahead of the axle if there is room. I'll get a good idea of that once I pull the motor and trans out of the car. Sounds like you know 911s pretty well. I also just looked at both the Cobra forum project page and their video. It's pretty wild that they are running that big Model 3 battery in that Cobra. Superfast Matt will also be an excellent resource. Thank you thank you! I learned quite a bit this evening.
 

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Looks like there are some conversions out there, where the Model 3 motor got installed upside down, so that the motor sits behind the diff, like its the case for the Model S motor.

I am also planning a 991 conversion (993 in my case) and would prefer the M3 DU. But I think installing it upside down is not the best idea. E.g. the Oil pump will be sitting at the highest point, so I will probably end up with a large Model S DU.
 

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Discussion Starter · #8 ·
Looks like there are some conversions out there, where the Model 3 motor got installed upside down, so that the motor sits behind the diff, like its the case for the Model S motor.

I am also planning a 991 conversion (993 in my case) and would prefer the M3 DU. But I think installing it upside down is not the best idea. E.g. the Oil pump will be sitting at the highest point, so I will probably end up with a large Model S DU.
I'm anxious to take some measurements once the engine and trans is pulled out of the 996. I'm really hoping there is enough room for the Model 3 rear drive unit ahead of the rear axle. I know the 993 is a bit smaller than the 996. I'll post some pictures here with the tape measure underneath to see if that Model 3 unit will fit, maybe it will help you out. Also, I know you have to have that oil pump at the bottom.

I think the 993 is one of the best looking cars out there. Do you have one with a blown motor?
 

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I'm anxious to take some measurements once the engine and trans is pulled out of the 996. I'm really hoping there is enough room for the Model 3 rear drive unit ahead of the rear axle. I know the 993 is a bit smaller than the 996. I'll post some pictures here with the tape measure underneath to see if that Model 3 unit will fit, maybe it will help you out. Also, I know you have to have that oil pump at the bottom.

I think the 993 is one of the best looking cars out there. Do you have one with a blown motor?
Crossing my fingers :) if it doesn't fit in your car, it wont fit in mine for sure...
I bought a 993 with missing engine, transmission, speedo, DME and some other stuff, so perfect for a conversion. Its still in the container in the US and waiting for sailing to Europe. This container shortage is very annoying. Latest ETA is Christmas.

I guess I will open another thread to not hijack yours :)
 

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Discussion Starter · #10 ·
Marc, I'm excited to follow your project! I'm hoping to have the engine out of the 996 this week and start measuring. I have a feeling I need to get some CAD software soon. I was able to find a cad file of the Model 3 rear drive unit on Grabcad so that's a nice place to start.
 

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Discussion Starter · #11 ·
Hi All, I made a video yesterday summarizing some of my research over the last week and an initial plan. For the battery, I was thinking the B-Class 36 kwh pack would work well with the Model 3 RDU, but I chatted with Zero EV in the UK (after posting this vid) and they advised me to look at other options. They said that pack is not high performance and would only give 150hp peak. They recommended a 35kWh pack made of 16 x CALB 2p6s modules. I need to learn a bit more about these CALB modules. I'm hoping to pull the engine and transmission from the silver 996 this week and start measuring to make sure there is room for the Model 3 RDU.

 

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Nice Video :)
The B Class Battery is an awesome pack. Have one here, its a strange form factor, but quite compact. Unfortunately its only 84s, so the optimal voltage for the Tesla DU's (96s) is not reached. Maybe one could use one pack plus two modules. But hard to source two similar old packs. Also only will be able to do 3/4th of the current of the M3 DU.
Its a good pack for a bug, but for a Porsche the power of the M3 DU should be used :)

Its really not easy to find a compact pack for it. My conclusion was to use either a BMW i3 pack or VW ID3 battery. Both are 96s and nice OEM Modules. i3 Pack prices are going through the roof in Europe, though.
Also a Model 3 LFP was offered to me, but from the Munro video it looks like the Modules can't be taken apart easily.

If it should be really cheap and range doesn't matter, the Chevrolet Volt hybrid pack would be good. But for me that would be too low range.
 

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Discussion Starter · #13 ·
Marc, this is excellent info. Thank you! I need to do some more research on the Volt and i3 packs, maybe I could run two Volt packs in parallel to help with range. It seems the i3 pack is not too expensive, the 33kWh pack would probably be enough range for me, plus I want to keep the weight down.
 

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Discussion Starter · #14 · (Edited)
Hi All, I'm looking for information on the different battery packs out there that would run the Model 3 rear drive unit. I've been advised that I need a 96s battery so that I can meet the 350V requirement of the Model 3 rear PM electric motor. Marc02228 recommended the Volt, ID3, and i3 packs, thank you! Is there any reason that I could not use Nissan Leaf battery modules? They seem to be cheaper.

Is there a nice list that shows information like size of modules, voltages, kwh, etc. for the common battery packs used for swaps? I just want to check before I make a spreadsheet. Thank you!!
 

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Have you been able to measure the space for motor and Battery already?
At least on the 993, neither the M3 Motor, nor the large Model s motor does fit. M3 DU doesn’t fit die to the rear seats, the large S DU due to the subframe that’s carrying the suspension.
Looks like the small S DU does fit, but I only tested with the subframe parts, as the car is on the way, still.
Will be very interesting to see if the 996 is that much larger that one of the other DUs fit. Crossing my fingers!!

here some info about the leaf packs:
 

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Discussion Starter · #16 ·
Marc, I will be continuing to remove the 996 engine and transmission this weekend and then start measuring to see what will fit. I hope to have the engine out this weekend or next. I also have my fingers crossed. It would be so nice to fit the Model 3 rear drive unit. Thanks for the pdf on the Leaf Modules. Have you thought more about what battery modules you will use for your project? I'm curious if you plan to put all the modules in one location or split them up?
 

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Discussion Starter · #18 ·
Hi All, does anyone know if Tesla drive-shafts have a unique spline type? I'm wondering if there is any possibility a Porsche drive shaft may fit the Tesla drive unit?

I'm in the process of buying a Tesla small rear drive unit and wondering if I should get the Tesla axles too? Thanks!
 

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Hi All, does anyone know if Tesla drive-shafts have a unique spline type? I'm wondering if there is any possibility a Porsche drive shaft may fit the Tesla drive unit?

I'm in the process of buying a Tesla small rear drive unit and wondering if I should get the Tesla axles too?
If a Porsche axle shaft would simply fit in a Tesla transaxle, why would companies such as Zero EV offer stub axles to fit the Tesla transaxle and connect to a Porsche axle shaft?

Porsche transaxles generally have output flanges to which the inboard CV joint of the axle shaft bolts; the available conversion stub axles have splines to fit the Tesla transaxle on one end and the VW/Porsche-style flange on the other end. The conversion stub axle provides the flange that the Tesla transaxle doesn't have; the Porsche axle shaft doesn't have a spline (to fit anything, Tesla or otherwise) on the inboard end.

To adapt the Porsche axle CV joints to the Tesla transaxle, you could buy Tesla axle shafts, use just the inboard end, and modify them to have a flange to which the CV joint bolts (which is what Yabert did for the similar situation in his VW van with a Chevrolet Bolt drive unit)... or you could just buy that part from Zero EV or someone else.
 

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Discussion Starter · #20 ·
@brian_ Thank you Brian! This was super helpful information. I did find the stub axles from ZeroEV so it makes sense that you can't just insert Porsche axles into a Tesla drive unit. I ordered a Model S small rear drive unit this week and had them throw in the axles so I am going to try to modify those to make them work with the Porsche axles. Thanks again!
 
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