# Porsche 911 EV conversion



## Breadvan (May 2, 2019)

Hi,

I'm also in the process of researching and planning a 996 EV build. I already have a 996 Targa which is too good to remove the ICE.....for now at least. Therefore I'm looking for another 996 with failed engine for transplant. 

I am however swayed more towards a Tesla drive unit conversion. 

Please continue to share pics and vids.

Thanks!

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## Tremelune (Dec 8, 2009)

You certainly won't have to worry about bore scoring and IMS bearings with the Leaf motor...

Are you planning on replacing the transaxle as well? The Leaf motor sits in front of the axles, such that you might be able to make it a mid-engine car without much modification to the chassis, depending on how much of the motor stack you keep together. Maybe it's fine to run it backwards, depending on cooling...?

What's the plan for locating the battery? Seems like you'd either lose the rear seat (which is almost for show anyway) or wind up with 500 pounds over the front axle.

Interesting project!


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## coleasterling (Feb 29, 2012)

1998? I thought the first year of the 996 was 99?


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## Breadvan (May 2, 2019)

https://en.m.wikipedia.org/wiki/Porsche_996

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## coleasterling (Feb 29, 2012)

I missed that he is in the UK. We didn't get the 996 until '99 in the US.


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## favguy (May 2, 2008)

I'll be watching with interest, 911 is on my shortlist for future conversion as well 

Does anyone happen to know if there are actually any issues with running the leaf motor in reverse?


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## brian_ (Feb 7, 2017)

favguy said:


> Does anyone happen to know if there are actually any issues with running the leaf motor in reverse?


The motor almost certainly won't care. If using the complete drive unit (motor plus transaxle), the transaxle will presumably not lubricate or cool properly if run continuously in reverse. The gear lubrication system would need to be examined to understand the consequences of reverse rotation.


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## stephenknox (Aug 17, 2018)

I'm keeping an eye on this with interest! 

Where in the UK are you based? I'd love to meet up, lend a hand talk conversions. I'm planning an RX-8 conversion.


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## VW-McG (Apr 4, 2018)

Okay, sorry for keeping you all in suspense, finally finding time to give some updates.

I'm still running the project as two stand alone streams, but we are getting closer to bringing them together.

With the car, most of the effort has been cosmetic on the car, this has mainly been to make space in the garage so I can put the car in there when it comes time to drop the engine. I have done a full interior swap on the car which was a good way to get to know the car better (and also see if there were any hidden areas of rust or anything like that...it was fortunately all pretty sound)

Removing the interior part 1
https://youtu.be/joCE__rTvEo

Removing the interior part 2
https://youtu.be/MU8sOquTJOM

Removing the dashboard
https://youtu.be/vmAsy9yQIbA

With the Motor the effort has mainly been around trying to get it running on the bench. I have the bench set up complete and have built a software controlled precharge circuit I can use, but I am struggling a bit with the CAN communication. While I continue to work through that, I will probably order a drop in board from the Open Source Inverter guys (which was going to be phase 2 anyway) so the project isn't held up.

Precharge Circuit using a software controlled relay board
https://youtu.be/RcIAnKZcI3I

Bench test set up
https://youtu.be/Su7C_k5vAR4

First attempt at bench testing the motor....fail.
https://youtu.be/z_2Ekn73VLs


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## VW-McG (Apr 4, 2018)

Tremelune said:


> You certainly won't have to worry about bore scoring and IMS bearings with the Leaf motor...
> 
> Are you planning on replacing the transaxle as well? The Leaf motor sits in front of the axles, such that you might be able to make it a mid-engine car without much modification to the chassis, depending on how much of the motor stack you keep together. Maybe it's fine to run it backwards, depending on cooling...?
> 
> ...


That's a very fair question and one I have just started planning around.

I am planning to use the Leaf transaxle and it looks like I may be able to mount it where the transmission for the Porsche is, in the same orientation as it was designed to go in the leaf (i.e. Motor in front of the drive shafts)

https://youtu.be/ECsGQvckjss

With regards to the battery, if I can fit the motor where I plan to, the space where the engine and exhaust were will be available for batteries, as will some space in the front where the petrol tank is. Depending on the size of the cells I end up going for, the central tunnel may also offer some space (this is a standard RWD model, so there is no drive shaft going towards the front wheels.


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## VW-McG (Apr 4, 2018)

Just wanted to give an update on this as it's been a few months since I last posted.* I've ended up spending most of my limited free time working on the project so I have been making progress.

I'm taking an agile approach to this, trying to get things in place and working in some way, shape or form so I can get this car moving, with the view that I can redo some of the work at a later date to make things more permanent, stronger, or just better.

I spent a good few weeks trying to figure out the best layout and orientation for the motor, and ended up having to take a cutoff wheel to part of the motor casing to allow it to fit.* I decided to run the Leaf motor and gearbox together, rather than trying to run it through the existing tiptronic gearbox and ended up pivoting the leaf motor 180 degrees horizontally to make it fit in the space.* The rear seat buckets encroached too much into the space where the gearbox was to make it possible any other way.* This means I need to run the motor in reverse so I will need to add some sort of transmission fluid scavenge system to get the fluid to the right parts of the leaf gearbox, but that's a challenge for another week.

For the current set up, I created some brackets that I could mount the standard leaf motor mounting brackets to so we can hold the motor in place and test it, but in the longer term, I plan to combine the motor mounting into the batter box.
https://youtu.be/qNyH4bAYlyg
With the motor held in place, I was able to focus on starting to integrate the motor into the car, that meant looking at electrical connections and drive shafts.* I built a custom loom to manage the various signals to the inverter and installed it in the car and I chopped and welded the four halfshafts I had (2 Nissan, 2 Porsche) to make 2 shafts with Porsche CV joints on the outside and Nissan Leaf CV joints on the inside.

https://youtu.be/omQoT16heVg
https://youtu.be/4luDauouFOA
*
Since then the effort has been to get the other components in place, mainly the inverter and precharge circuit and most recently to put in a bunch of small lead acid batteries to use as a test battery back.
https://youtu.be/c11UwZrgFmg

With that all in place and now fully wired up, I am running out of ways to put off actually trying to run the motor in the car.
I am doing a complete check of the wiring now, but once that is done, I think my only option is to switch it all on, send power to the inverter, press the accelerator pedal and hope for the best.

​​​​​​​I'll let you know how I get on.*


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## Tremelune (Dec 8, 2009)

Nice! What are your range goals and battery plans?


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## VW-McG (Apr 4, 2018)

Thanks.

Battery goals will probably end up being iterative. I would love to get a good bit over the 100 mile mark, so I am keeping my eye out for something like a reasonably priced 120ah BMW battery pack, but there don't seem to be many doing the rounds yet. I may end up going for something much smaller in the short term so I can at least test the car properly and play around with performance. 

I'm considering getting a couple of Mitsubishi or Mercedes PHEV battery packs to make a small generic test pack that I can use for this and any future projects during shakedown while I look for a full size pack.

If I do end up going that route, I am looking at ways to make it modular so I can easily work with different voltages for different projects. (i.e. multiple c150v sub packs that can be connected in series or parallel depending on what I am trying to do.)

But it's all theory at the moment

Need to get the car running so I can make space in the workshop to be able to build a battery box and mounting hardware.


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## ebryane (Aug 25, 2019)

I watched your videos of the motor placement a number of times, that looked like a lot of work but you persisted! I have a similar application that I hope to start in the next few months (rear drive car (not Porsche), potentially a leaf driveline). I have two questions if you have the time:



- Did you consider keeping the same upright arrangement with motor in front of transaxle but shifting the package back a bit? The BAJA VW crowd runs lifted suspensions using a rear drive transaxle that create a significant angle on the CV joints. The angles get close to 20 degrees (seems pretty big if you look at pictures). I'm wondering if instead of orientating the differential end of the axle above the tire at 20 degrees to the shaft, if you were to do it fore/aft would that solve your fitment issues? These folks use fancy hardened Porsche CV's (maybe because of operation, maybe because of these angles), and I believe these angles lead to inefficiencies, but it may make it easier to mount the Leaf motor/diff without flipping it as you did (?).



- I have heard that the leaf motor will only run up to 25 MPH backwards, have you heard differently? I'm still trying to absorb information....



Very anxious for your next posts


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## VW-McG (Apr 4, 2018)

I tried a lot of options for keeping the motor in the standard orientation, but the CV joints would have just ended up too far back. It would have resulted in far too much of a lateral angle than I was happy with, and it also would have ended up fouling on the Porsche subframe that the suspension components mount to.

The main challenge running it in reverse is going to be to ensure good lubrication in the gearbox, I am considering some sort of scavenge pump set up to get the transmission fluid to the right places to keep the bearings lubricated.

I can well imagine that Nissan would have limited the reverse speed to a low value in their software. There shouldn't be any physical/electrical limitation in the inverter and motor so I am hoping that with the right parameters set on my replacement logic board I can get it to run smoothly in the opposite direction to normal.

Best of luck with your upcoming project.


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## VW-McG (Apr 4, 2018)

Got the wheels turning


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## brian_ (Feb 7, 2017)

VW-McG said:


> I tried a lot of options for keeping the motor in the standard orientation, but the CV joints would have just ended up too far back. It would have resulted in far too much of a lateral angle than I was happy with, and it also would have ended up fouling on the Porsche subframe that the suspension components mount to.


This is the first Porsche conversion that I've seen with a modern suspension. Usually they're working with the old semi-trailing arms, and only a motor placement behind the axle line is viable. This suspension design is entirely different, but still intended for a rear engine so it's not surprising that the motor still fits only behind the axle line, and a Tesla Model S/X unit is the obvious choice. Any of the drive units which place the motor concentric with the axle (which means mostly the Chevrolet Spark EV and Bolt so far, but more are coming) are also possibilities, but there is always the problem of interference between the drive unit and suspension; custom subframes can help that, but there's no easy fix for a suspension pivot point landing in a motor or gearbox case.

There have been Tesla drive units mounted with Corvette (C5) suspensions, but this requires a custom frame and is only viable with a wide vehicle.

Some Porsche rear suspensions - apparently including the 996 - have left and right side cast aluminum structures which could be moved further apart by using wider structural components between them. For a vehicle which can handle the increased track width, this is a potential approach.
This is a complete rear suspension corner:








... and here is the other side of the suspension and from another perspective, showing where the cast aluminum arch (which I assume goes over the transaxle) bolts in:








Even if not moving them apart, the arch between these sides should be practical to modify as necessary (or replace with a fabricated steel part) for clearance; the cast side frames should probably remain intact.


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## brian_ (Feb 7, 2017)

VW-McG said:


> With the motor held in place, I was able to focus on starting to integrate the motor into the car, that meant looking at electrical connections and drive shafts.* I built a custom loom to manage the various signals to the inverter and installed it in the car and I chopped and welded the four halfshafts I had (2 Nissan, 2 Porsche) to make 2 shafts with Porsche CV joints on the outside and Nissan Leaf CV joints on the inside.


I understand that this is a temporary arrangement, but welding chopped-off axle half-shafts together seems like just as much work than just doing it properly. In his Westfalia T3 with Chevy Bolt drivetrain, Yabert showed how the inner CV joint cup (his are Chevrolet Bolt, but the Leaf is similar) can be cut off and have a flange welded to it to accept VW/Porsche style inner joints.


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