LDU vs. Model 3 Rear Motor

[ekohn04]

Hi everyone, I've been working on a conversion for a while now and have completed everything needed to prepare my car to install an electric motor. Now I just need to buy one. I'm struggling to decide between two options. For reference I have a 62kwh Leaf Pack

1. Purchasing a base LDU from a semi-local dealer for $2500, then using Damien's board to control it for a total of ~$3000
2. Purchasing a Model 3/Y rear motor from eBay for around $2000, and then purchasing a unit similar to EV controls or Ingenext's control unit for a total of ~$3200.

The questions I have are as follows:

When Tesla switched from a RWD to AWD system for the 3, did they change the rear motor or use the same unit like they did with the S? This will help me understand if the motors that I'm seeing on eBay are the same as in the RWD system, allowing me to use the existing performance metrics from the Model 3 and then apply that 0-60 (and other metrics) to the expected performance in my conversion.

Is anyone aware of the performance difference of these motors once swapped into a car? (existing projects of swapping each respective motor that might be similar enough to compare)

Will the efficiency gain with the Model 3 motor be enough to justify the loss of performance?

Is the customizability that comes with Damiens board worth opting to the LDU for?

Any comments are welcome. This community has been immensely helpful through the duration of my project, I just want to thank everyone here.

[Doig5710]

Hey it probably depends how you want to control the motor and what you want to do with it.
If you want to go racing or lots of quick driving may be best imo to go with the model 3 motor, as its better cooling and efficiency will allow more performance over a longer period of time. I have gone this way with my conversion because it'll end up as a race car one day. The down side is that at this stage there is no open inverter control system other than the 2 fully commercial ones you have listed which will probably do everything most people require at a price.

If its more of a road car with occasional fast driving or squirts of power then a LDU would be fine as you can use the EVBMW board to control it however you want.

As far as i know you will be able to get all the full power out of both motors whichever way you choose to go as long as the battery and cooling systems are up to it.

The M3 has a couple of different versions of rear motor with slightly different power levels and a front motor as well so plenty to choose from there for layout options in your vehicle.

Worth a read is this one on #dougyip cobra race car which has run with both a LDU and a M3 motor.
viewtopic.php?p=26410&hilit=dougyip#p26410

Hope this is a bit helpful whichever way you choose to go

[P.S.Mangelsdorf]

Here are my thoughts, based on my understanding of both motors. I'm sort of thinking out loud here, so bear with me.

The LDU and SDU are distinct from both M3 motors, which are distinct from each other, front to rear. To the best of my knowledge, the community's knowledge about what motors Tesla put in what, and when they made substantial changes to motors is a bit limited after 2017, when they introduced the M3 and it's motors, and began integrating them into other platforms as well. My understanding is that the M3 only has one rear motor type and one front motor type, but because Tesla does not have true model years and release very little information publicly, we really can only figure that out by checking individual cars and motors.

If I was picking a motor today, I'd still go with the LDU. The LDU is more powerful than the M3 motor. Many more people have used the LDU, so there is greater support for it when it comes to tuning and potential issues. However, I believe the LDU is heavier, and is definitely bulkier.

Like Doig5710 said, you should think about what you want to use the car for. Drag racing? LDU. Road racing? M3. Daily driving? Toss up. Big car? LDU. Mid to small car? M3.

Given your Leaf pack, it is unlikely you will be able to use the full power potential of the LDU. You might want to at least consider an SDU. Like the LDU, it's fairly well supported, but it has the benefit of being smaller and lighter like the M3.

[ScythianNite]

I think packaging is going to be your biggest hurdle more than performance. I went with the M3 980 motor and plan to use the ingenext controller (for now) with OI tesla charger and zombieverter controlling everything else in the car. Because of the controller requirements, i needed to source a tesla 3 brake switch and throttle pedal, as well as the OE motor harness. Thankfully i was able to get the motor harness and HV cable with the motor, but overall this entire setup is going to cost closer to 6000 than 3000 USD. A drawback i currently have is that the M3 motors don't have readily available axle stubs like the LDU/SDU does so I will need to send out a cut/spliced CV shaft to get made into something I can use for my application.

overall for my application I couldn't use an LDU without divorcing the inverter and any model S/X motor would have needed to be flipped which meant i'd need to deal with the oil pump changes to run them backwards. M3 fit my packaging requirements perfectly so that's what I went with

[P.S.Mangelsdorf]

I went with the M3 980 motor and plan to use the ingenext controller (for now) with OI tesla charger and zombieverter controlling everything else in the car. Because of the controller requirements, i needed to source a tesla 3 brake switch and throttle pedal, as well as the OE motor harness. Thankfully i was able to get the motor harness and HV cable with the motor, but overall this entire setup is going to cost closer to 6000 than 3000 USD.

This is a good point. Sourcing ancillary components can get difficult. OpenInverter on the LDU is a bit easier in that regard, because it is adaptable. For example, I use a Chevy Trailblazer throttle I got from the junkyard for a couple bucks because it was the easiest to get out of the car in the yard and mount in my own. I just had to do the throttle calibration procedure. I did source a stock tesla harness for the LDU connection, but you don't have to, the information for each connection is available. You could even make your own HV cables and just figure out how to properly seal them, though that could be a challenge.

[ekohn04]

Thanks for the replies everyone! I'm putting the motor in a BMW E30 for reference. I just bought an open inverter board and will probably source an LDU from a local supplier. The lower cost and the greater database of support for the LDU greatly influenced my decision, as well as the hardware limitations mentioned that accompany M3 motor (pedals, axels, etc.). Now to wait for the board to arrive... any experience with shipping times lately?

[SuperV8]

Thanks for the replies everyone! I'm putting the motor in a BMW E30 for reference. I just bought an open inverter board and will probably source an LDU from a local supplier. The lower cost and the greater database of support for the LDU greatly influenced my decision, as well as the hardware limitations mentioned that accompany M3 motor (pedals, axels, etc.). Now to wait for the board to arrive... any experience with shipping times lately?

Have a read here to know what potential problems you may have with an LDU:
viewtopic.php?t=2242

The SDU is still powerful for a road car (unless you are going drag racing), and much lighter than the LDU - and I don't believe have the rotor seal issues of the LDU?

[evolver1566]

BTW, the Ingenext and EV Controls pieces are more like US $4k... just saying.

[PerpetualForeigner]

I know this is an older thread, but I thought I'd ask here since the topic is about M3 SRDU vs MS LDU...

Trying to decide between an LDU or an MS SDU/M3 SRDU for a conversion project. I love the raw power of the LDU, even given the weight, but bristle at the idea of having to gamble on getting a motor that might be leaky or has a messed up rotor shaft. So either the M3's SRDU with the more efficient PM design or the MS SDU are also on the table. Does anyone know if the the outboard splines of the M3 axles are the same as those of the LDU? (I'm assuming they aren't but I'm hoping against hopes that they are...)