Would You Electrify Your Compact Sports Car?

Slippery (Forum Supporter) said:

Keith Tanner said:

How did they do it? Stick a motor on the front of the trans and fill the trunk with batteries? Or did they do it properly?

Not sure what properly means, kind of subjective but there is no transmission. 

Tesla motor sitting where the factory fuel tank goes, between the passenger area and trunk. Batteries where the engine used to be. 

Its a one off, so they most likely did not go for the perfected design aimed at the masses. 

So Tesla motor coupled directly to the diff, or in place of? I'm not familiar with either platform well enough to know what the packaging is like. A retrofit directly to the diff seems off-hand like a decent way to keep some gearing flexibility with diff ratios. 

Keith, since you've clearly given it some thought, how would you do it the "proper" way with an ND? Is the only caveat that you'd need some flexibility in the battery packaging that doesn't exist at a realistic price for something like this?

Edit: are all Tesla motors like this one? If so, seems like the diff would go away in a small rwd vehicle like the s2000.

In theory you could make the batteries "disconnectable". So you could have spots along the body where you can take a bunch of battery weight out for a 60sec autocross run, and then put them all back in for the drive home. 

My e36 drives ~100 miles roundtrip at the farthest these days. My S52 isn't in great health. If these questions were all answered YES, then I would do it

Will it be the speed or quicker to 60?

Will it cost less than similar performance from an LS?

Will I be able to package it without losing trunk/interior space?

Will it be as easy or easier to convert than aforementioned LS?

At the moment, there are a few NOs in there that are kinda deal breakers for me.

bluej (Forum Supporter) said:

Slippery (Forum Supporter) said:

Keith Tanner said:

How did they do it? Stick a motor on the front of the trans and fill the trunk with batteries? Or did they do it properly?

Not sure what properly means, kind of subjective but there is no transmission. 

Tesla motor sitting where the factory fuel tank goes, between the passenger area and trunk. Batteries where the engine used to be. 

Its a one off, so they most likely did not go for the perfected design aimed at the masses. 

So Tesla motor coupled directly to the diff, or in place of? I'm not familiar with either platform well enough to know what the packaging is like. A retrofit directly to the diff seems off-hand like a decent way to keep some gearing flexibility with diff ratios. 

Keith, since you've clearly given it some thought, how would you do it the "proper" way with an ND? Is the only caveat that you'd need some flexibility in the battery packaging that doesn't exist at a realistic price for something like this?

Edit: are all Tesla motors like this one? If so, seems like the diff would go away in a small rwd vehicle like the s2000.

Basically, replace the differential with what you see in the picture. It already has a gearbox to drop the output speed into the right range and a differential inside. With the flat torque curve of the electric motor gearing becomes less of an issue. Just stick some halfshafts into that thing and you're good to go.

In an ND, you can't fit an Model S motor (like the one above) in the rear subframe without interfering with the rear upper control arm pickup points. A bigger car like an NC or an S2000, maybe. But a Model 3 motor would fit in the ND, which is where my 250 hp suggestion came from. Then you have the trans tunnel and everything forward of the firewall for batteries, cooling, etc. I can't remember how much of the fuel tank area you'd need.

Vajingo, the problem with pulling batteries for a minimum weight banzai run is that you'd lose performance as well. Each battery has a limit to how fast it can discharge. Double the batteries, you have double the amount of energy that can be discharged over a given time and thus more power. Would that be enough to offset the weight loss? That would be really interesting to find out.

It's going to be a long, long time before EV performance is cheaper than using a 20-year-old gasoline motor out of a truck that was made by the millions. Eventually. But if sheer speed per dollar is a factor, it's hard to beat cutting apart a trashed Camero and using a welder to jam those parts into something else.

As someone who effectively owns the same car in both ICE and EV modes (E39 M5 and dual motor Model 3) - EV performance is not bland. It's quieter and doesn't smell as much, but it's not bland. It just doesn't make as much of a fuss about getting stuff done, and it gets it done faster. If you like throttle response, you can't not like an EV.

In reply to Keith Tanner :

Thanks.

Keith Tanner said:

Vajingo, the problem with pulling batteries for a minimum weight banzai run is that you'd lose performance as well. Each battery has a limit to how fast it can discharge. Double the batteries, you have double the amount of energy that can be discharged over a given time and thus more power. Would that be enough to offset the weight loss? That would be really interesting to find out.

 You can influence this a bit by the design of the batteries (engineering trade-off between power capacity and total energy storage) but yes.  This is why the Teslas with higher energy storage capacities also go faster, which was confusing to me when I first encountered it.

I'll add that the neato "whhhrrrrrrrr" is a fun sound. It's not a fun sound like an F1 engine, but it's a more fun sound than lots of pedestrian ICE cars.

I have thought about electrifying the Alto Works more than once.   If I could keep the weight down and find a place for the batteries without cutting it up, I would do it.

A friend of mine is in the middle of repowering his STS Miata to electric.

I'm repowering my turbo Miata to a newer engine and bigger turbo.

I did reach out to WestEV (purveyors of EV swap kits for old sports cars) about doing a swap for the Miata.  I even offered up mine as a test mule.   They said they had zero interest in catering to the Miata crowd and they were happy building 1970's Porsches.  (Cause the dozen or so of those needing EV swaps is a better business model than a MILLION FREAKING MIATAS)

KyAllroad (Jeremy) (Forum Supporter) said:

A friend of mine is in the middle of repowering his STS Miata to electric.

 

I'm repowering my turbo Miata to a newer engine and bigger turbo.

 

I did reach out to WestEV (purveyors of EV swap kits for old sports cars) about doing a swap for the Miata.  I even offered up mine as a test mule.   They said they had zero interest in catering to the Miata crowd and they were happy building 1970's Porsches.  (Cause the dozen or so of those needing EV swaps is a better business model than a MILLION FREAKING MIATAS)

"Whaddya mean, $20k for the conversion? But I only paid $1500 for the car!"

alfadriver (Forum Supporter) said:

... Weight is a problem.  But not the job stopper for me.  Cost is...

Agree on both.

I've looked into designing an electric "sports car" from scratch and while it's perfectly doable, at the end of the day, I'm not sure it's what I want. It would end up essentially a tube frame Model 3. Figure it would weight mid to high 2xxx lbs at least, though for autocross, a bunch of batteries could be removed, but would you be happy having built a trailer queen? Autocross heavily favors light weight, and it's just not.

Speaking of batteries, I think that it's fair to say that most people would prefer to leave the battery assembly intact, which means putting it in the floor where it is in Teslas (S model, not sure where it is in the Model 3). That does mean that this "sports car" gets taller, though the heavy bit is now down low. It also means that we're back up to the high 2000's at least, for weight.

Regarding cost, around here, Tesla drivetrains (and enough battery to make it worthwhile) is $10-12K. Money-wise—and weight-wise—it's hard not to compare it to instead dropping in an LS drivetrain.

Yes, a lot of instant torque. Yes, it's quiet. But no, I'm not sure it adds up. That said, everyone's "equations" are different. What's most important to you?

Oh, and yeah, there's also the increasing number of YouTube videos showing battery packs going off in a very impressive show-of-force. Yes, gasoline is flammable, too, but at this stage, fearing a whole lot of energy in those little cells is still warranted.

To the original question: Absolutely.

I have pipe dreams of electrifying old cars and selling them as a business. Of course, reality sets in, and one of the big stumbling blocks is liability/safety. I'd hate to kill a hipster in a battery fire I was responsible for. Also, hate the lawsuits sure to follow.

Still, I'm hugely interested. I think of Altimas/Sentra SERs, with their propensity to eat cats until they die. Should be really cheap, right? Slapping an electric motor on that 6 speed LSD transaxle sounds proper. 

Of course, you get back to the ideas already stated, and circular logic leads to analysis paralysis.

I want to build a motorcycle, but kinda think a bicycle might be a better place to start.

In reference to the custom battery cell thing, I've been you tubing, and I believe a diy battery pack, custom configured to application is doable. Safely doable, I dunno.

Interesting discussion, seems like there has been some thoughts kicking around on this.

That Tesla3 drivetrain is interesting, and would easily plop into the back of an AW11.

Keith, maybe you have some insight here, do you know the physical volume that the cells in a Telsa3 take up? I know fundamentally the design is different, but I do wonder if there are options there to change the design to be a bit more modular to fit in the lower portions of a car in various locations to achieve the range/power that would make the conversion worth it.

Also, cost isn't really on my radar right now, mainly armchair engineering here.

mad_machine (Forum Supporter) said:

I have thought this would be great for either my Saab or the Fiat Spider.  The Saab would be interesting as it would allow me to ditch the made of glass transaxle.

Ha! Same for me for at least one of my '80s 900s.

"light weight is important for autocross" = true, but that's assuming you have the same CoG and torque vectoring ability. Check out how Model 3s do in autocross despite the fact that they weigh as much as a Camero convertible :) They have a low CoG and their torque vectoring is really good in large part because of the fidelity of the information and the speed of response.

I'm hoping that GM will be our source for truly modular batteries. The Model 3 power packs (like all of them) are made of individual cells that are joined into packs for cooling and wiring. And it's that cooling that I think is going to be the challenge if you want to change their shape.  Luckily, they're the most generic part of the whole shebang so there are still options developing.

I don't know how much you can disassemble from here, but to me it looks like a Model 3 has four long, skinny packs. Stuff two in the transmission tunnel of a converted car, maybe? That's a 75 KWh pack that weighs right around 1000 lbs. From that teardown page:

 the two modules on either side are 67.5 in (1715 mm) long and weight 191 lbs (86.6 kg) each and the two center modules are a bit longer and heavier i.e. 73 in (1854 mm) and 207 lbs (98.9 kg). All four modules are 11.5 in (292 mm) wide and 3.5 in (90 mm) thick.

So whats the weight delta from an NA Miata?  Assuming you are ditching the trans, engine, and driveshaft, thats... what 400lb?  So +400lb (batteries) and ??lbs (motor/diff difference) more for the Tesla stuff (and a gigantic performance increase)

It seems like on bigger iron-block cars you could almost directly replace the engine/trans with batteries and diff with a tesla motor and keep them weight neutral-ish, esp with say a 60kwhr pack.

You'd save more weight doing the swap on an NA than an ND because the stock drivetrain is heavier. I figured a 500 lb weight gain with the ND, the NA might be closer to 350. That's off-the-cuff, I'm not looking up the weights right now.

I think my '66 Cadillac would be an excellent EV. Really, it's all the same characteristics that GM was looking for in the first place: silent and full of torks.

Would be a hoot in my VW thing.....

Would probably become my daily if it could happen without me electrocuting myself installing it.

While I am getting my shop fixed up so I can get back to working on my Rabbit, I have been researching/scrounging to figure out how to do the conversion to AWD. It is looking like it makes the most sense to electrify the rear (looking at Smart parts, so far) and run as a hybrid with maybe 20 mile or so plug in range. Down th road I can either ICE swap again or go full electric.

I know that before the electronics were one of the  problems , 

have any of the pure Evs "software" been cracked  or adapted to work in another car ?

I know this was a problem with Tesla , but I also believe the Smart Ecars and Fiat 500E , 

I would think to keep it a "sports car" you want the corner weight right and battery weight down low, 

Keith Tanner said:

I think my '66 Cadillac would be an excellent EV. Really, it's all the same characteristics that GM was looking for in the first place: silent and full of torks.

This is more along the lines of what I'm coming around to. Like ProDarwin says, stuff with heavy drivetrains, and stuff that's heavy anyway, not Miatas, VWs and Porsches, but Malaise era cars, wagons, Explorers-stuff that is going to be discarded anyway.

 or

and, of course, 

Keith Tanner said:

"light weight is important for autocross" = true, but that's assuming you have the same CoG and torque vectoring ability. Check out how Model 3s do in autocross despite the fact that they weigh as much as a Camero convertible :) They have a low CoG and their torque vectoring is really good in large part because of the fidelity of the information and the speed of response.

I'm hoping that GM will be our source for truly modular batteries. The Model 3 power packs (like all of them) are made of individual cells that are joined into packs for cooling and wiring. And it's that cooling that I think is going to be the challenge if you want to change their shape.  Luckily, they're the most generic part of the whole shebang so there are still options developing.

I don't know how much you can disassemble from here, but to me it looks like a Model 3 has four long, skinny packs. Stuff two in the transmission tunnel of a converted car, maybe? That's a 75 KWh pack that weighs right around 1000 lbs. From that teardown page:

 the two modules on either side are 67.5 in (1715 mm) long and weight 191 lbs (86.6 kg) each and the two center modules are a bit longer and heavier i.e. 73 in (1854 mm) and 207 lbs (98.9 kg). All four modules are 11.5 in (292 mm) wide and 3.5 in (90 mm) thick.

Wonder if those would fit on their sides in the drivetrain tunnel in a Miata (or FD or RX-8) thanks to the depth required for the powerplant frame.

In reply to wheelsmithy (Joe-with-an-L) (Forum Supporter) :

you're forgetting the pickemup trucks

If only I had a Miata on my lift right now. Wait a second...

Eyeballing, I think you could fit three of them in a Miata tunnel. I'll back that up with a tape measure soon.

As for software, there are third party controllers that can run a Tesla Model S power unit. Not the 3 yet to the best of my knowledge. Pity, because the 3 motors are very clearly 2-3 generations further along in evolution although they're not as monstrously strong.