# Variations on a Tesla theme



## eUKenGB (Feb 21, 2019)

I'm thinking about the use of a LARGE Drive Unit in an EV project, but seeking confirmation on some of the spec differences.

Would I be correct in thinking that all LDUs are mechanically the same?
Are the different performance variations done with just software and/or different controllers/inverters?
The ~600 Nm torque figure is from just the motor and therefore about 9x that at the wheels?
There is no Model 3 (PM) motor that can match the above torque figure?
Info on the above would be much appreciated.


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## brian_ (Feb 7, 2017)

As far as I know yes, although there was a recent announcement of an upgrade which would replace the mechanically driven oil pump with an electric pump in one of Tesla's drive units.
The power and torque limits of those variations are due in large part to battery size and refinement in how hard they are willing to push the thermal limits of the motors and batteries; I have not heard of any difference in the actual motors within a given size (large or small).
Yes... but torque for AWD models could be reported as total of front and rear motors.
Since the Model 3 is limited by battery, inverter, and software configuration like any other model, ultimate power and torque limits are unknown... but presumably Tesla doesn't offer a Model 3 configured for the motor torque output of the higher-output Model S variants.


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## eUKenGB (Feb 21, 2019)

Thanks brian_, as I thought.


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## remy_martian (Feb 4, 2019)

2. For the Model S/X LDU, the "sport" variant uses a different inverter. AFAIK, the rest of the unit is the same.

I'm not sure if the CAN codes are the same. Something has to ID back the kind of unit that's back there, I'd think, but for our purposes, that message shouldn't matter.


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## tks007 (Feb 16, 2020)

The LDU reports maximum limits for power and regen. So the sport edition could simply report a bigger value back.


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## remy_martian (Feb 4, 2019)

Are those simply acknowledging commanded limits as an echo response or is it updating based on temperature, etc?


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## Isaac97 (Jun 3, 2019)

I believe it's echoing limits received from the BMS. 
The LDU is controlled directly via the pedal, so it enforces the BMS limits; it seems to have limits of its own as well, but these are different for the different units. 
Jason Hughes flashed a regular unit to sport and got more power (don't have a source for that, it was on teslamotorsclub somewhere).


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## remy_martian (Feb 4, 2019)

You _can _flash a regular unit to sport, but you run the risk of cooking the inverter because it uses cheaper electronics. You'll also get a lot more sag at the motor, so there's diminishing returns to be had if you do it, anyway.


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## eUKenGB (Feb 21, 2019)

remy_martian said:


> …You'll also get a lot more sag at the motor…


Sag? I'm not familiar with that term. Can you clarify?


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## eUKenGB (Feb 21, 2019)

A technical question:-

Take 2 Tesla LDUs. One is the standard and the other the 'sports' version that can make more torque (and hence power) and let's say hook them up with identical batteries so they are not a factor determining the outcome of this comparison.

When running these 2 motors side by side, i.e. not actually using the greater performance potential of the sports motor, would they both drain the batteries at the same rate? Or would the greater potential of the sports version mean it always uses a bit more all the time, as does an ICE for which greater potential always means using more fuel all the time even when not using that potential.

I'm just trying to get it clear in my head how electric motors use energy. I suspect a physically larger motor with greater potential would quite possibly use more all the time, but the same actual motor, just with electronics that can support that greater potential would actually use the same amount of energy at the same usage level as the motor with more restrictive electronic controls.

So there would actually be no downside to using the high performance/sports version of a Tesla LDU (apart from cost maybe)?

Hope that was clear. Simple question in my head, not so easy to articulate in the written word.


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## remy_martian (Feb 4, 2019)

eUKenGB said:


> Sag? I'm not familiar with that term. Can you clarify?


Voltage sag. 

When you pull a lot of current from a system, the terminal voltages at the motor can drop.


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## remy_martian (Feb 4, 2019)

eUKenGB said:


> A technical question:-
> 
> Take 2 Tesla LDUs. One is the standard and the other the 'sports' version that can make more torque (and hence power) and let's say hook them up with identical batteries so they are not a factor determining the outcome of this comparison.
> 
> ...


The Sport will be more efficient and will drain the battery LESS.

Mind blown?


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## eUKenGB (Feb 21, 2019)

remy_martian said:


> The Sport will be more efficient and will drain the battery LESS.
> 
> Mind blown?


Not blown, no. Find it rather interesting though. So the 'sport' version uses a more efficient inverter etc which has a greater max. limit of power to the motor and uses less electrical power for the same output power. So definitely would be the one to go for then - if you can find one of course.


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## remy_martian (Feb 4, 2019)

Quite a premium to pay for one....


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## eUKenGB (Feb 21, 2019)

remy_martian said:


> Quite a premium to pay for one....


Indeed, plus presumably there would be a higher minimum battery capacity to provide the higher power.


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## Isaac97 (Jun 3, 2019)

remy_martian said:


> The Sport will be more efficient and will drain the battery LESS.
> 
> Mind blown?


Really?
IGBTs have a constant voltage drop which is more or less irrelevant to size.
Tesla uses the smaller front motor when they want better efficiency.
You probably know something I don't, could you explain a little more?


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## eUKenGB (Feb 21, 2019)

Just looking at the various motors. Comparing the max. torque (which is the most relevant comparison of 'grunt'), the regular LDU puts out 441 Nm with the Sports version lifting that to 600 Nm. But what's interesting is that the Model 3 is 450 Nm, so slightly more than the regular LDU and with the undoubted increase in efficiency from its more modern design, that must make it a good candidate for use in any conversion that can accept the motor in front of the drive axle.

Having said that, from the information I have, the Model 3 motor has slightly taller gearing which means torque output of the drive assembly is slightly less than the regular LDU. Remarkably similar output in fact to that of the Small DU.

With a lot of Model 3s being sold, definitely interesting, but although I've seen a few questions about this, has anyone yet actually cracked the Model 3 motors for use in non Teslas?


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## Isaac97 (Jun 3, 2019)

Damien Maguire is working on it. He has been able to spin one up and is working on a modboard. There will be lots of tuning to do, but it's coming.


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## eUKenGB (Feb 21, 2019)

Isaac97 said:


> Damien Maguire is working on it. He has been able to spin one up and is working on a modboard. There will be lots of tuning to do, but it's coming…


I thought I'd seen something about that, so good news.

Thinking more about the different Tesla DUs, the S/X Small DU and that from the Model 3 are extremely similar in performance. However is the later more modern design of the Model 3 apparent in its efficiency. With essentially the same performance, does the Model 3 DU suck less power from the batteries, hence providing greater range (than an S/X SDU) from the same capacity of batteries?

I realise it's kinda hard to measure since the Model 3 is much lighter than the S and/or X and also may use improved batteries, but is there any empirical evidence of the Model 3's DU being more energy efficient?


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## Isaac97 (Jun 3, 2019)

Model 3 DU seems to be a little more efficient because the Raven S/X (3 DU up front, regular LDU in rear) are more efficient/have longer range. But that might also be due to other factors, like the improved adaptive suspension.
Permanent magnet motors are generally slightly more efficient because flux does not need to be generated electrically, being created by the magnets. 
Tesla is upgrading Model S/X with new, more efficient electric motors - Electrek
This claims a 4% difference - 97% vs 93%. Some of that may also be from the SiC inverter.


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## eUKenGB (Feb 21, 2019)

So a PM 'sports' LDU might be on the horizon. Now that might be worth waiting for and hopefully Damien's Model 3 work can be transposed onto these new larger motors.


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## Isaac97 (Jun 3, 2019)

Hmm.. It's possible. The induction motors are generally cheaper to manufacture and can handle higher heat levels - if a PM rotor gets too hot it will demagnetize and become useless. So they can be run harder without damage. Maybe Plaid includes something of the sort - possibly 3 M3 motors? That would be very cool.


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## eUKenGB (Feb 21, 2019)

Isaac97 said:


> …The induction motors are generally cheaper to manufacture and can handle higher heat levels - if a PM rotor gets too hot it will demagnetize and become useless. So they can be run harder without damage…


I presume you mean it's the induction motors that can be run harder.

I would imagine any new large PM DUs would be much sought after and hence expensive, while perhaps the earlier induction ones might reduce in price a touch.

All of which means an early regular LDU might make the best option. Particularly if you could bump it up to 'sports' capability to be able to use the extra performance for quick bursts. Continuous high demand would probably be problematic if used like that, but surely for just short bursts might be Ok. Most bang for the buck is the ultimate goal of course.


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## Isaac97 (Jun 3, 2019)

Older technology might reduce in price. Then again it might become rare, since they are relatively easy to reuse and their performance is well known.
Induction motors are generally easier to control with a DIY board, PM gets problematic especially when tuning the first one.

Advances in the OEM world are always great for us DIYers, remember when a DC motor was the ultimate power? And cost 2k? I don't miss that at all. Now for that money we get a whole drivetrain with 300HP.


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## remy_martian (Feb 4, 2019)

The LDU hovered at $10k for almost forever, then took a nosedive to $3k when the M3 started production.

Damned shame the battery modules from M3 are so darned unweildy.


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## P.S.Mangelsdorf (Dec 1, 2014)

remy_martian said:


> 2. For the Model S/X LDU, the "sport" variant uses a different inverter.


Is there actually any confirmation on that? I haven't seen anyone with a sport and non-sport on the bench together to compare the inverter internals, just lots of conjecture. It seems that some people, such as wk057, found it to only be a firmware limit, at least as I understand his Tesla Motors Club posts. So those of us using Damien's replacement board will be unlimited.


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## eUKenGB (Feb 21, 2019)

P.S.Mangelsdorf said:


> Is there actually any confirmation on that? I haven't seen anyone with a sport and non-sport on the bench together to compare the inverter internals, just lots of conjecture. It seems that some people, such as wk057, found it to only be a firmware limit, at least as I understand his Tesla Motors Club posts. So those of us using Damien's replacement board will be unlimited.


Yes, a very good question, to which I'd really like to know the answer.


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## remy_martian (Feb 4, 2019)

I'm pretty sure I heard Damien say the output transistors were different


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