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Introducing our 1987 Porsche 924S EV Conversion

15781 Views 90 Replies 17 Participants Last post by  lordmundi
I've been lurking on the threads for quite a while but want to introduce our father-son EV conversion project on our 1987 Porsche 924S (which my son has affectionately named "Perl"). We are super excited to make steady progress toward our 80's inspired EV conversion.
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I am not a Porsche guy, so I have been surprised by just how much I've enjoyed learning about the Porsche 924 and 944 and their history, not to mention the community around them and just how much people love them, warts and all.

We searched for a car for a while - our criteria being something aerodynamic, light weight, manual transmission, interior and exterior in decent shape but a blown or missing engine. Luckily, we found one in Perl!

What we have done so far - removed the engine, removed the exhaust, cleaned up the engine bay, got all of the lights working and mostly converted to LED, started rebuilding the brakes, and removed the transaxle (so that we can remove the fuel tank). It's been so much fun learning about each piece. We also 3d printed a cover for our torque tube and 3d printed a model of a hyper9 motor to assess how it might fit in the front.
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Where we are and questions we have - so we are about to invest in a motor/inverter and batteries. While I was initially thinking a Hyper9, I've recently become much more interested in the Nissan Leaf motor (I think it will fit better in the engine bay and will be much more affordable). If we do go with the hyper9, i think we would need to shorten the drive shaft to let the motor fit behind the front cross-member of the car, which isn't a huge deal but not super fun either. But in terms of the Nissan Leaf motor, I've been researching and trying to understand options like the openinverter project, and the thunderstruct VCU etc. My issue is every time I search for things on the leaf motor I see tons of threads and videos and I'm not sure what the more recent advice is. I know that so much development has been done in the last few years I guess I'm not sure on what the most current experiences are in dealing with a leaf motor, and what batteries and controllers are being used. Maybe my google-fu is just poor to find the most recent stuff.

Along with trying to find that information (mainly to just give me confidence to go make some purchases), I'm also a little curious about people using batteries with the leaf motor. The specs I'm reading say that motor normally runs with high voltages - something like 350 - 400V from the leaf batteries. How are people generating voltages that high? Are you forced to use the leaf batteries so that the voltage is that high? Or is there some way to use tesla battery modules and not require an insane amount of them in series? I guess I'm just looking for any experiences people know about in terms of what battery packs for an leaf motor EV conversion look like.

Other problems I haven't sorted out in my head yet - how can I at least get enough heater capability such that you can defrost the windshield (which is a safety issue)? Also, if I put a large amount of weight in the rear of the car (more than the weight of a full gas tank), can I just buy stiffer or adjustable shocks?

If anyone has any advice or insight we would love to hear it. We are really looking forward to learning and making memories with this project and hopefully sharing it with everyone else.
  • Our automotive skill level: moderate (I know my way around cars a bit, but haven't ever restored a car from top to bottom)
  • Electricity skills: I have a background in electrical engineering, although I know just enough to be dangerous.
  • Range goal: just something reasonable for driving around Houston. I think if we can get 100 mile range that would be great
  • Performance: nothing insane. Just something fun to drive.
  • Money: whatever it reasonably takes to get something working and make memories with my son.
  • Parts we are considering: Nissan Leaf motor. Not sure on batteries.
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That's a great test bench! The keyed e-stop is a pretty cool idea too.
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Um, any chance you'd be willing/able to measure those gearbox-to-engine bolts? Need to order one size longer to mount a brace under the head..
Yeah length from underside of the head to the end would be awesome, thank you. From measuring the motor I have figured out that they are M10x1.5 but not sure about length. Guessing about 60mm? Just want to see if I can confirm before going out hunting for more.
That's perfect, thank you so much!

Good point about dissimilar metals, will have to look into that as well, I suppose. Much appreciated!
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I do have some of the bolts that hold the motor mount to the gearbox housing, took a closer look at them just now. They are larger diameter and shorter in length, but they also thread into aluminum. They are magnetic, and have grade 10.9 stamped into the head. They are also coated with something that looks friggin' exactly like the aluminum castings. Hot dip maybe? What I may do is order 2 bolts a bit longer for a bracket, and hit the junkyard to zip the other 4 bolts out of some other cars. Looks like they are common on a ton of other models (Sentra, Versa, Altima etc).

And for anyone in Canada, the damn things are $9/ea at the dealerships up here, but I bet these would be a good replacement:
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Is the pump motor resting on the housing? Wouldn't be something like that or the tank rattling?

You could drop a few bucks on an automotive stethoscope or even put your ear to the back of a big screwdriver and poke around a bit. First step is to localize it imo. I'd probably start by listening around the bearings in the reducer.
I don't think the motor would be it, the pawl is spring loaded and the actuator uses a spring detent and a compression spring. But if you can localize the sound to a specific location, it should point you in the right direction?
Good stuff. 3.9v seems just a bit high for long term storage FYI, so if you figure it's going to be a while you might want to let them run down a bit closer to 3.7 during testing. I couldn't really find an exact recommended storage voltage for this exact battery, but that seems to be a reasonably safe number. Are you planning to do water cooling? Via the OEM radiator or something smaller?
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Hmm, one thought about the fuse.. That front module is 24s which is one satellite's worth of cells, so if you put it between there and the rest of the pack, you would still have the ability to pull it and make the pack voltage slightly lower for safety's sake, without blowing the bms (I think).
Cool, congrats on the milestone, guys!

Did that continued spinning turn out to be some kind of unintended regen without any load on the motor? I know the openinverter guys have trouble with that sometimes.
Great detective work! Love the scope, too. Freeze frame capability looks like a very handy thing to have!
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Oh damn that's cool. Looking forward to the model processing video. Always wondered what that workflow is really like...
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