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Discussion Starter #1
Been in the EV game for quite a few years now. Have only had electric motorcycle conversions (can see these on Elmoto.net) and this is my first car build. Being in Ohio the MC sits unused to often due to weather or desire to gear up. So I'm getting rid of the bike and upgrading to a car. I do also have a 2016 Volt that is my daily driver.

My first thoughts had me looking at Miata/RX7/MR2 size cars, but I decided I wanted a bit more room in the car and would love a backseat for a bit more utility. This lead me to 3000GT or 300ZX. The other 3 cars hold there value better than the 300ZX and the 300ZX is only slight less efficient (weight+aero). Found a 300ZX about an hour away and picked it last week. Good interior, decent/rust free body and blown, but in place engine. Picked it up for $1200.

It is a 1993 2+2 NA, auto vehicle.

Towing was an adventure and within the first week the only key snapped in half, so I'm off to a great start. :rolleyes:

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Here are the interesting details. Current plan (but I will discuss other options too)

Tesla drive unit in the rear, replaces rear diff and fuel tank area. Haven't decided on large vs small unit yet. Depends on price/room.

Batteries will be some used EV cells. Dont want to go tesla modules first time around due to cost mainly. Other EV batteries can be had for half the cost. Will be something like Volt, i3, eGolf, or Soul EV cells most likely. All these cells can produce decent power (10C+) and are mostly available.

Plan to use power steering, ac compressor, ptc heater, and brake pump from a production EV or hybrid. Haven't spec'd these out yet.

Goals are to be faster than the stock TT (300HP) and get 100-200mile range eventually. Hoping to keep it under 3500lbs.

Next few months will be tearing the car apart and weighing everything. Thanks for reading -Kyle
 

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Tesla drive unit in the rear, replaces rear diff and fuel tank area.
One challenge in using Tesla drive units is making them fit with a suspension which was not designed for them. It's straightforward with semi-trailing arm designs (like old VW, BMW, Mercedes, etc), but not with modern multi-link suspensions. The 300ZX might not be too bad to fit (because the control arms don't run much behind the axle line)... except that the Super HICAS active rear steering won't fit with the Tesla motor in place, and even fixed track rods might be a challenge.
 

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Discussion Starter #3
One challenge in using Tesla drive units is making them fit with a suspension which was not designed for them. It's straightforward with semi-trailing arm designs (like old VW, BMW, Mercedes, etc), but not with modern multi-link suspensions. The 300ZX might not be too bad to fit (because the control arms don't run much behind the axle line)... except that the Super HICAS active rear steering won't fit with the Tesla motor in place, and even fixed track rods might be a challenge.
Agreed, the hardest part of this whole build will be modifying the rear subframe to fit the drive unit. Do not have an exact plan right now

See this picture


Behind the diff is the fuel tank. So the trickiest part is clearing the rear subframe mounting points with the controller/motor casing while maintaining axle position. I will have the car up on jacks in a few weeks to measure/investigate further.

This is a non-turbo so no HICAS on board. I would have deleted it either way. Not worth the weight and complexity.
 

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This is a non-turbo so no HICAS on board. I would have deleted it either way.
That's fortunate (for the conversion). The track rods (barely visible in the photo) are still an issue: their mounting points are likely to interfere with motor or inverter housing, and if you change their length or mounting points you'll change the bump steer behaviour.
 

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See this picture
Could you put some dimension on that picture? I could then try overlaying the Tesla 'small' rear drive unit for you... would at least tell you whether that's an option worth pursuing.

Note: given the majority of the drive unit is 'behind' the driveshafts it looks as if it would fit to me :cool:
 

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Note: given the majority of the drive unit is 'behind' the driveshafts it looks as if it would fit to me :cool:
That's the fortunate characteristic which I mentioned a few posts ago: the Tesla drive unit is mostly behind the axle line, while the suspension is mostly ahead of it. :)

With a rear track of 1534 mm, and tire section width of 225 mm, it's 1310 mm between the tires, or 655 mm from centreline to tire. The motor appears to extend about 340 mm outward from the centreline

Now, look at the track rod. It is at roughly the height of the axle shaft, and extends inboard to somewhere close to the inner CV joint... closer to the centre line of the car than to the inboard face of the wheel. On the motor side of the Tesla unit, that looks like it will be close to, if not into, the motor housing.

If it all fits, great. I'm just suggesting a serious look at the packaging, and overlaying dimensionally correct images would certainly help.

Is the Tesla S/X front drive unit narrower than even the smaller rear unit, perhaps to provide more tire clearance for steering? If that's true, then it may be a better candidate for some of these challenging installations (even though it places the motor significantly higher, potentially causing other fit problems).
 

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Discussion Starter #7 (Edited)
I’ll get a dimensional picture tomorrow, but you motivated me to lift the car and take measurements. Rear frame mounts are 27” on center and they are about 6.5” from the center of the driveshaft.

And the rear axle center could move 2” rearward without hitting. I need to look closer at the axle angle and what the max is allowable.

Thanks for the images of the smaller drive unit


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Rear frame mounts are 27” on center and they are about 6.5” from the center of the driveshaft.
If I'm reading the photo correctly, 27” on centre would put the mount at the 3-inch mark on the tape measure in Kevin's second photo... right on the end of the motor housing. The motor housing appears to start about 3" rearward of the axle centre line, so 6.5" back from the axle line would be well into or beside the motor. Tesla does appear to run the axle shafts at a substantial angle to allow the motor to sit further forward (because it fits between the parts of the suspension designed to work with it); the shafts could be run at a similar angle in the other direction to allow the motor to sit rearward, although suspension travel will further increase the joint angles in that case. Also keep in mind that's the centre of the mount, not the outside of the mount or that chunk of subframe.

The track rod end is further rearward than the subframe mount, and so in greater conflict with the motor housing.
 

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Hi Nuts

Don't worry too much about moving the Tesla motor a bit further back - you do need to check that the combined extra angle plus the suspension movement is not too much but I bet you have a ton to play with

As far as the rear subframe that the suspension mounts to - just cut it all away and make up your own frame to get everything into the right position

Looks like you will have plenty of room!

And that leaves the whole transmission tunnel for batteries - all the way through to where the radiator used to be
Leaf modules are 35 mm thick - I bet that you could have a 60 module long stack (30 kWhrs) just in that space with enough room for two smaller stacks - one each side in the engine bay

AND all of that plus the motor is right on the floor - so your C of G will be a lot lower than the origional

IF your C of G is lower then you may not need the anti-roll bars - I have the mountings for the anti-roll bars on my car but I simply don't need them
 

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Discussion Starter #10
Yes, the tunnel will be wide open for batteries. That's in the plan. Leaf cells are lower on my list due to cost mainly, but I would consider the 30kWh packs if I find one at the right price.

Also yea I think I would blow away the rear of the subframe including the two mount points. With a combination of increasing axle angle, lower profile bushing mounts, and a small tilt of the motor things should fit. The bigger hurdle is the toe rod that has been discussed that needs shortened or relocated in some manner.
See the some info on the 300ZX here (https://conceptzperformance.com/blog/suspension-101-300zx-edition/). I need to keep reading, but it looks like the geometry matters to limit bumpsteer. I may be wrong,but it appears that the current setup doesn't follow the general rules anyways.

Anyone have the height dimensions of the small drive unit so that I can confirm ground clearances? I will do my best make a solid model of the small drive unit over the next week using those dimensional images. I'll also model up the axle/mounting points. very crudely at least.

Next step is to compare to the large drive unit (I saw the other thread with good dimensions), just to be thorough on whats possible. :D
 

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The bigger hurdle is the toe rod that has been discussed that needs shortened or relocated in some manner.
I agree. If the motor interferes with the track/toe rod, perhaps an arm can be arranged on the hub carrier going forward, placing the rod ahead of the axle line rather than behind it.
 

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See the some info on the 300ZX here (https://conceptzperformance.com/blog/suspension-101-300zx-edition/). I need to keep reading, but it looks like the geometry matters to limit bumpsteer. I may be wrong,but it appears that the current setup doesn't follow the general rules anyways.
If it helps, you can think of the combination of the rear upper control arm and what they call the "traction rod" as forming a virtual upper A-arm (with the virtual ball joint at the intersection of the centrelines of these two arms). The Toe Rod is the steering link.

It looks like the passive toe rod is shorter than the links of the active Super HICAS system. That suggests that one of them is not ideal for bump-steer, but they're similar.

I don't see anything "against the rules" about this design. Compared to a typical front double-A-arm suspension, the arms trail (face rearward) an unusual amount - that certainly doesn't stop it from working properly, and is probably done either to enable more anti-squat, or to provide less toe change due to bushing compliance under acceleration and braking loads.

Yes, the geometry matters. As the suspension moves vertically the hub carrier moves laterally and bit longitudinally; the track rod needs to complement this movement, so it needs to be comparable in both length and angle to the other arms (lower control arm and effective upper A-arm). To be effective, it must attach to the hub carrier well off of the steering axis (the line through the lower ball joint and effective upper pivot point)... but that can be behind or ahead of the axle line.
 

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Looking for more information on this suspension, I ran across an enthusiast's website collection of images. Some of the drawings might be handy for planning component layout.


Nothing to do with EV conversion, but I found this interesting...

While the rear suspension is a relatively common modern multi-link design, the front suspension is outright freaky. It is essentially a double-A-arm design, but with the (extended) hub carrier split so it can rotate around the steering axis, so that the outboard end of the (short) upper arm can have a single-axis pivot instead of a ball joint. This is halfway between a normal ball-joint suspension and a kingpin type. It gave Nissan interesting opportunities for geometry, but I would want make sure those two pivot pins (between the upper and lower hub carriers, and at the upper arm outboard end) have minimal play! The ball joint normally used for this function has nearly zero compliance or free play.
 

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One more observation from a fan of mechanical design: the Z32-generation 300ZX appears to use the same rear suspension as the S13-generation 240SX (and other S-platform models of that generation... but I've only seen the 240SX because it was the only one sold in North America). This means that when Nuts&Volts works out the Tesla drive unit swap, the same design will work for the S13 240SX (and the nearly identical S14 240SX)... if anyone can pry one out of the hands of a drifting enthusiast. ;)

The 240SX is narrower than the 300ZX, and lighter (although that might be mostly due to the difference in engines).
 

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Discussion Starter #15
So overall it seems I will be able to find a solution to fitting a unit. In a few weeks time I will have the engine/etc. out and be able to take more accurate measurements of things. At that point I'll dig in hard on the rear subframe redesign.

My hope is for a small rear drive unit or a large rear drive unit. I'm keeping my eyes open for a deal in the next two months.

So using HSR as my baseline I'm trying to figure out what the units can handle assuming I use DIY control board that lets me set my own limits. All Tesla units can handle 404V max in the Tesla's 96s battery pack and I assume the drive control units are designed with 600V components. Anyone think its worth the extra power potential to run 100s or 102s on these units.

On the current side of things I see a small unit is rated at 650Adc and large non performances is rated at 950Adc on the input. Havent seen anything about output current. Anyone have any info? What do we think we can get out of a small rear drive unit?

On the vehicle side of things I have a few tasks. New front bumper, new spoiler, new taillights, headlights need a little repair. A few small rust spots to clean up near the rear of the car. Those are the major things.
 

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Hi
Speak to Kevin Sharpe (username) about the open source performance of Tesla drives. He and a bunch of guys (and gals?) are doing great work on this and should have practical advice for you.

Cheers

Tyler
 

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Hi Nuts & Volts While you are sizing it all up consider using the whole suspension package. The whole rear end, or even the whole front end installed in the rear. That way all the geometry is done for you and all you have to manufacture is 4 or 6 bolt up points. It might work.
 

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Discussion Starter #18
Hi Nuts & Volts While you are sizing it all up consider using the whole suspension package. The whole rear end, or even the whole front end installed in the rear. That way all the geometry is done for you and all you have to manufacture is 4 or 6 bolt up points. It might work.


I’ve considered this and plan to look into that more closely once I pull the rear subframe off the frame. I like this idea, except for cost. I have the resources (software, tools, friend with a welder, etc) to retrofit existing subframe and some steel tubing shouldn’t cost too much ($500). Add $500 for custom axles, decent estimate? I’m afraid a full subframe/suspension will run be another $2000 minimum, plus I’ll still need some metalwork. I love the idea, just hard to justify the cost.

Additionally the Model S rear track is 6.5” greater than the 300. 67” vs 60.5”. That’s a lot to overcome. Even the front is 65.5” track. Need to take into account wheel offsets, wheel width and body spacing to get the full picture

Anyone else have input about using the full Model S rear end?

-Kyle


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For a vehicle with a very wide track, the stock Tesla suspension makes sense to me.

Narrowing this suspension with just wheel offset changes would certainly hurt geometry, and is unlikely to be practical for a significant track difference. Narrowing this suspension by making shorter arms seems pointless, since you would be basically building a whole new suspension, as well as needing shorter axles. Narrowing this suspension by mounting the inboard ends of the arms further inboard seems very unlikely to work, because the rear mounts will run into the drive unit.
 

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I have the large drive unit, its about 120cm wide so you might have some trouble fitting it. Its certainly possible but you will have more work to redesign the original suspension. As for using the tesla subframe, what are the rules like in your area? + 7inch wide rear end is a fair bit but maybe a tastey wide body body kit might look nice?

I think the small drive unit would fit with some minor massaging of the left hand subframe mount, but its going to be some work either way so get what you really want and make it work from there :)
 
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