Would You Electrify Your Compact Sports Car?

I love the cacophony that is the morning of race day. One of the things I will never forget is roaming around the Sebring paddock on race day as all manner of displacements, cylinder count, and crankshaft designs fire to life. It's loud, it's sometimes abrasive, but it's alive and there is a magic there with the sounds and smells that can never be replicated.

But, the world is changing, and the attraction of electricity is something that I never imagined that I would say I'd be interested in, but I'm finding myself more and more intrigued with the electrification of classic compact sports cars. I was far less attracted to it until I realized that you could actually attach that motor to a real transmission: https://youtu.be/VdPQueOPT4A

The dumbing down of such a conversion (e.g. Turn car on, push pedal, go) was enough to keep me away for a long time. But the idea that you can now essentially replace the ICE with a pony keg of wound copper and your fuel tank with a load of cells while still keeping quite a bit of the tactile sensations that make driving a car actually driving a car, well that changes things. Range still seems bad, but things will improve, I'm sure. 

Has anyone ever crunched the numbers on this for weight? I have an AW11, which has a nice, heavy iron block, but a small fuel tank, plus all the normal things you wouldn't need (radiator, piping, etc.). Without knowing really what one of those DC motors would weigh, I'm not going to make any conjecture on how the numbers would balance out, but I'm wondering if you get close to the factory weight while loading up the fuel tank cavity with cells. Maybe you'd need to spill over into the frunk, but there'd be plenty of room up there too.

Fundamentally, It also seems like you could do this without having to hack apart your car, which is also attractive.

Anyways, morning coffee thoughts. Interested to hear what the hive thinks.

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.

I've been saying for years that I can't wait for my Nissan LEAF to die so I can shove its powertrain into a Miata or a wishbone Civic or something. 

I've been thinking about this for the better part of 15 years. Battery tech keeps getting better and therefore cheaper and lighter. 

But I don't think "similar to stock weight" is really going to be possible unless you're only going for very short or very slow drives (or both). 

for example, a nissan leaf battery pack (24 kwh) apparently weighs 675 lbs or so. If you're removing an engine (but keeping transaxle) and replacing with an electric motor, you probably lose 300 lbs (assuming about 400 for the engine and exhaust and fuel system, adding back 100 for the electric motor).

but, adding only 300-400 lbs is pretty good, and if the leaf goes far enough on a charge for your use case it could work. I'd bet you could do even better theoretically with used Tesla stuff. 

I am really starting to like the idea of converting something from the radwood era with a digital dash. 

An electric XT6 or something similar would fulfill the 80s vision of the future pretty well. 

Robbie (Forum Supporter) said:

I've been thinking about this for the better part of 15 years. Battery tech keeps getting better and therefore cheaper and lighter. 

But I don't think "similar to stock weight" is really going to be possible unless you're only going for very short or very slow drives (or both). 

for example, a nissan leaf battery pack (24 kwh) apparently weighs 675 lbs or so. If you're removing an engine (but keeping transaxle) and replacing with an electric motor, you probably lose 300 lbs (assuming about 400 for the engine and exhaust and fuel system, adding back 100 for the electric motor).

but, adding only 300-400 lbs is pretty good, and if the leaf goes far enough on a charge for your use case it could work. I'd bet you could do even better theoretically with used Tesla stuff. 

Teslas are actually really heavy. The Leaf would not need a transaxle, but it would be underpowered compared to the Tesla stuff. It would likely have more power then the original though.

I'm in. I can see both being really fun.

Dual motor CRX?  Yes please

tuna55 said:

Robbie (Forum Supporter) said:

I've been thinking about this for the better part of 15 years. Battery tech keeps getting better and therefore cheaper and lighter. 

But I don't think "similar to stock weight" is really going to be possible unless you're only going for very short or very slow drives (or both). 

for example, a nissan leaf battery pack (24 kwh) apparently weighs 675 lbs or so. If you're removing an engine (but keeping transaxle) and replacing with an electric motor, you probably lose 300 lbs (assuming about 400 for the engine and exhaust and fuel system, adding back 100 for the electric motor).

but, adding only 300-400 lbs is pretty good, and if the leaf goes far enough on a charge for your use case it could work. I'd bet you could do even better theoretically with used Tesla stuff. 

Teslas are actually really heavy. The Leaf would not need a transaxle, but it would be underpowered compared to the Tesla stuff. It would likely have more power then the original though.

I'm in. I can see both being really fun.

Fun fact, a Model 3 dual motor weighs almost exactly the same as an E39 M5. Very similar performance on the standard metrics, too.

I've run some rough numbers and come up with 2800 lbs for an ND Miata that's been converted to an EV using a Model 3 rear motor in the rear subframe. 250-ish hp, 200 mile range. That's a similar power/weight ratio as an S2000, but with a much fatter torque curve. The range is what drives the weight and cost in large part, you just keep piling in batteries (see what I did there?) until you get where you want to be. More batteries also means more power for the motor because they can deliver energy faster.

Keith Tanner said:

tuna55 said:

Robbie (Forum Supporter) said:

I've been thinking about this for the better part of 15 years. Battery tech keeps getting better and therefore cheaper and lighter. 

But I don't think "similar to stock weight" is really going to be possible unless you're only going for very short or very slow drives (or both). 

for example, a nissan leaf battery pack (24 kwh) apparently weighs 675 lbs or so. If you're removing an engine (but keeping transaxle) and replacing with an electric motor, you probably lose 300 lbs (assuming about 400 for the engine and exhaust and fuel system, adding back 100 for the electric motor).

but, adding only 300-400 lbs is pretty good, and if the leaf goes far enough on a charge for your use case it could work. I'd bet you could do even better theoretically with used Tesla stuff. 

Teslas are actually really heavy. The Leaf would not need a transaxle, but it would be underpowered compared to the Tesla stuff. It would likely have more power then the original though.

I'm in. I can see both being really fun.

Fun fact, a Model 3 dual motor weighs almost exactly the same as an E39 M5. Very similar performance on the standard metrics, too.

I've run some rough numbers and come up with 2800 lbs for an ND Miata that's been converted to an EV using a Model 3 rear motor in the rear subframe. 250-ish hp, 200 mile range. That's a similar power/weight ratio as an S2000, but with a much fatter torque curve. The range is what drives the weight and cost in large part, you just keep piling in batteries (see what I did there?) until you get where you want to be. More batteries also means more power for the motor because they can deliver energy faster.

On the subject of batteries, don't forget that you lose the gas tank, light by itself, but the gasoline isn't, which is probably 50-100 lb for most of us most of the time.

I believe I took that into account. Cooling system, fuel, etc.

Keith Tanner said:

I believe I took that into account. Cooling system, fuel, etc.

No doubt. I quoted you because you reminded me. Robbie didn't put that in the equation above.

No, I would not electrify an existing gas-powered sports car.  Note that this is a different question than "would I buy a purpose-built electric sports car".

Why?  As noted above, with current technology, an EV drivetrain with a reasonable amount of range is going to add significant weight to the car, probably a minimum of 30%.  Tesla has shown that you can have a good-handling car with this weight penalty, but in order to accomplish that they have completely changed the way you package stuff with the "battery floor".  Put simply, you can't retrofit that to a chassis that was designed for a traditional gasoline engine.  The closest anyone's come to doing that is the original Tesla Roadster, which was based on an Elise.  I've never driven one, but the reviews that I've read all spend most of the pages talking about the effect on acceleration, skimming over the handling with few words which tend not to be terribly positive.

Furthermore, if you're talking about a personal, DIY conversion, you're also hampered by the need to use generic parts.  No custom-shaped battery packs that nestle around the existing components to make ideal use of the space, instead you have to make room for whatever you've got.  Look at gas-tank-to-fuel-cell conversions on club race cars to see how that works -- it's possible, but it's a ton of work cutting things out and welding in new structure, the end result is rarely "pretty", and even then it's still much less space-efficient than the factory design.

OTOH, I certainly think it's possible for an OEM to make a purpose-built electric sports car that uses the tech from EV family cars to deliver a modest-performing-but-fun-and-affordable sports car.  The electric version of a Miata, if you will.  Would I buy one?  I don't know, it would depend a lot on the details.

tuna55 said:

Keith Tanner said:

I believe I took that into account. Cooling system, fuel, etc.

No doubt. I quoted you because you reminded me. Robbie didn't put that in the equation above.

I didn't put it in expressly, but I did say fuel system. 

If your electric battery pack only goes 80 miles, you should only compare it to 80 miles of gas in the tank. in an AW11 MR2 that'd be what, 20-25 lbs? I still think my 300 lbs net estimate is probably pretty close. Adding energy storage capacity isn't a weight winner for the batteries. 

I loosely looked into it- just to get an idea.  

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

And second to that is safety- I've messed around with making a solar generator using LiFePO4 batteries, and even 36V it a lot.  Let alone- I punctured one accidently, and had to quickly rip it out of the bundle I had to prevent a larger battery short fire.  And that's a safe chemistry.

So to do it safely, I'd have to contract it out.  Which adds to the cost problem.

For the highly probable use of my Miata, a short range battery set up would be perfect.  But I can't bring myself to pony up that dough.

Simply put - no.  No good reason other than I have no interest in it.

Turn 14 and Rywire just did an S2000. Looks really good, except those weird wheels. 

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?

Yes I would.

I'm with Alfadriver on this one weight and cost make it a no go for me.

When my F500 was an exclusively an autocross car I thought  electric might be viable till I did the numbers; I was looking at a significant cost for no performance gain whatsoever.

I got all excited about doing this with the MGB GT that I have but do not use. Leading reason for not using is because you have to warm the thing up both in the drive and the road before it is really happy, then you get where you are going smelling of  exhaust fumes. The idea of a MGB GT golf cart that I could use to puddle jump around the hood and to the shops was appealing.

But not the 10k worth of appealing that I kept landing on.  MUCH more if I wanted any range that made it real transportation.

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. 

In reply to Slippery (Forum Supporter) :

that's what he means by properly. 

did they use the benefits of the electric motor directly? or did they force the electric motor into the pre-existing compromises of a totally different powerplant?

Yup. No vestigial power train components, that's done properly.  You can't go to a full skateboard with a conversion like this, so this is about the limit with current tech and a retrofit.

Now only if they'd started with a lighter car :)

I would do it one of 3 ways:

1) If I was dialing a car to 11.  No point in intermediate levels of performance.  Tube frame, battery floor, properly engineered.  Possibly hub motors.  Basically just the shell of the original car.

2) Some old cruiser that I wanted to bomb around town in, where performance/efficiency aren't really factors, but not dealing with an ancient powertrain is.

3) Race car to go after 24HOL $50k prize.

I'm literally in the middle of doubling my investment in my 1988 Mazda RX-7 Turbo II with an engine rebuild and a new clutch, and as long as I'm in there, I figure I'll rebuild the front suspension.  There isn't a chance that I'd ever trade the sounds and smells of a turbo rotary blasting the sweet, sweet aroma of incinerated dead dinosaurs out the exhaust pipe for the sterile blandness of an electric drivetrain.

So put me down for a "Nope!"