Syonyk

I've seen, somewhere, an electric drag RX-7 that was insanely fast.

I'm debating converting a '7 to an electric car. This would be the "around town" car - if it has a range of 50 miles, that's overkill. This would be for getting groceries, picking random people up, and generally being a quietly running nuisance.

Alternately, build it up a bit, put some insanely high powered electric motor in it, and have an electric autocross car (and around town car). Flat torque curve over the entire RPM range?

Anyone attempt this? I'm not sure a '7 would be the best car to use for an around town electric car, since it's fairly small with limited battery space, but it would certainly be fun.

-=Russ=-

pianoprodigy

You do that...

torean

there are other cars that would make a better choice.....stock 7s are what......2600-3000lbs.....try to find a crx or something lot lighter than a 7......

AusTexRex

Are you talking about changing out the entire powerplant to an electric one? If so, I'm sure it could be done with the correct transmission and engine + custom mounts. Though Cutting will most likely be involved on the firewall, and finding hte right transmisson to fit without having to raise the car or something will be hard.

As for making the car a hybrid (possible, but hard) the battery cell packs could be mounted in the hatch area, assuming you seal it correctly, and vent it through the back bumper.

torean

hahaha......lack of torque plus extra battery weight....what a good idea for a around town beater......if u want something with good pick up around town....u want tiny tiny wheels....13-14inches will do fine.....but hey.....go for it if u really want to

CodyHokieFD

We have an electric neon here at school. I am on the hybrid electric vehicle team for my senior design project. Its really intresting stuff and this year we are working on a competition for GM, hybridizing a chevy equinox and then competing against other schools. In your case i suppose it could be done, its just a matter of taking everything out, deciding where to put the battery pack, getting all the batteries, setting up the highvoltage stuff, somehow mounting the motor, and being able to control the thing. With my experiences at school, its a hell of a lot more difficult than it sounds. But I wish you the best of luck and if you have any specific questions I might be able to help you.



*** Id like to see a rear wheel drive electic seven, you could smoke the hell out of the tires with the torque you can produce from the motor. We have a vid of autocrossing the neon and thats just about all it does the whole time. haha Those electic motors produce max torque at 0 rpm which is pretty interesting. The way out neon is set up is front wheel drive and it is just a single gear setup as of right now i believe? So yeah if you have any questions let me know and ill get you the specifics....

SnowmanSteiner

Use a motor cycle engine as a generator to power the batteries then you can actually travel.

- Steiner

Syonyk

I'm talking about replacing the entire powerplant with a big electric motor and assorted batteries.

I'm thinking of just using the stock transmission, fabricating a plate that bolts to it, and has the motor mounted, and then ties into the stock engine mount locations to support everything. Realistically, you don't even need a transmission, since electric motors are so flexible. You can really just stick it in one gear and go, for the most part. It's easier to mount a motor to the transmission though, since you can just bolt to it. The only real modification would be taking the engine out and putting the electric motor and associated batteries/controllers in. Everything else would remain the same. You'd need a vacuum pump for the power brakes, and a separate motor to run the PS/AC (if you kept them).

I might try to find something lighter, but a RWD car would be the easiest to do this with, and I'm likely going to have a "spare" '7 floating around without an engine.

-=Russ=-

Syonyk

Would you like me to start yet another thread about sleepy headlights or removing my AFM or turboing a NA instead? :-P

-=Russ=-

CodyHokieFD

I say you go for it man, sounds like a sweet project, refer to the *edit in my previous post if you didnt see that...

Syonyk

Cody - I'd be interested in some basic stats on what you're using - battery array voltage, motor power/type, controller type, etc. It seems most people doing stuff like this use somewhere in the 144v range battery pack, an AC motor, and a big inverter/controller.

Any chance of getting that neon autox video hosted somewhere?

But, yes, I think it would be rather fun to drive. A '7 with torque down low... that'd just be weird.

-=Russ=-

Syonyk

That's not a bad idea either. Basically, an indirect drive hybrid. All the generator would have to do is create slightly more power than it takes to cruise at highway speeds. The batteries handle all the acceleration & such.

Also, Cody, do you know what the Neon is doing for regenerative braking (if it is at all)? That would be nice, but would add a lot of complexity to the controllers (and could be added later). Plus, doing the bulk of the braking with the rear tires could lead to some interesting handling.

-=Russ=-

CodyHokieFD

Well I dont know all the specifics off of the neon off of the top of my head since it is kind of our side project (it was the competition vehicle for 95, but we still play around with it). Let me see what I can find, and my team leader has that video and ill look into that too

CodyHokieFD

Ok i found the video on our ftp site, but I have no idea how to host it or upload it on here.....??

Swiftuh

Cool project. If I remember correctly, there was a NASCAR that was electric. Had one motor for every wheel. It was soon banned because of the performance being in a differant class. Electric power is way better than gas. The only downfall is the weight and size of the power supply. You have to have a clutch and tranny though. When coasting the magnetics in the motor will slow you way down. Custom gearing may be needed. You would have to build it just right. electric motors can have huge rpms. the last thing you would want, is you clutch, tranny, driveshaft, backend, ect exploading. so if you have any toughts of going over 10k on a 15 yearold car, you can forget it.

Personaly, my initial toughts would be to mount the batteries in the engine bay. Then figure out a clutch/ tranny system so you can have one battery on each back wheel.

yey dinner time

Syonyk

I'm planning to, at least initially, go with a very simple setup. Remove the motor, fabricate a heavy steel plate to go on the front of the transmission, mount the electric motor on this, and then brace it to the engine mounts. No clutch (really, no need to switch gears) or regenerative braking. A vacuum pump powers the brakes, and then several battery packs power the motor. Simple and easy - just batteries, a motor, and a controller. Since the motor will be driving through the transmission, the same general speeds will be used. Also, without the flywheel and clutch, the hazards of higher input speeds are significantly reduced. I don't expect to run the tranny at insanely high RPMs though. If the motor runs significantly above 8000 RPM, I'll gear it down before it hits the transmission input shaft.

If this works well, I'll see what else I can add. Regenerative braking is high on the list, as is a small motor/generator combo for longer driving. If I can get 20-30 miles of city driving on the batteries, I'll be happy - use them for acceleration and around town, then crank up the generator on the highway for longer cruising.

Weightwise, I think it will be about the same. Batteries are heavy, but the engine bay will be stripped of almost everything, which IIRC is around 400-500 lbs. Some batteries in the engine bay, and some in the rear "spare tire" area (and/or back of the hatch).

As much as independently driven wheels would rock, that's well beyond what I'm looking for, complexity-wise, in this project (for now). Using the existing drivetrain will allow for a very simple design. If I can get a fairly high output motor (in the 150-200 HP range), it should absolutely fly, because the motor will be generating full torque right off the line and pull all the way up. I'd like to autocross it, honestly.

As for this actually happening? Not sure. I'd like it to, but I need money first. It's an interesting idea, though.

Actually, random thought, would a first gen be better suited to it? I'd still have the same drivetrain arrangement, but I seem to recall there were some first gens that were really quite light.

-=Russ=-

CompuBob

I've been thinking about this for a long time, I would use the stock tranny and just figure out a way to get the flywheel bolted to the output shaft of the motor, cnc some mounts so it can attach to the tranny like the regular 13B does then make some more mounts so you can attach the electric motor to the stock 13B engine mount locations.. unless you wanted to go direct drive like a golf cart, then just mount it under the car directly to the differential input.
but the first way I described would leave the car as stock as it can be and you would still have your gears. Then with all the extra space you have under the hood get a generator to power on when you are driving at highway speeds where you wouldent notice the noise, muffle it to hell anyways.
also attach some alternators somehow to the rear half shafts so the momentum of the car at high speeds will regcharge the batteries.

well, thats my idea eventhough the general idea of it all has been mensioned already.. it's been in my head for years.

patman

iTrader: (3)

fi youre using an electric motor, a transmission is not really necessary. at the least, a suoer simple one could be used. problem is, batteries are heavy and super expensive. hybrids are better, but the main advantage of a hybrid is regenerative braking. basically, the only decent way to do what you are proposing is to completely redesign the whole car. it could be done with an rx7 chassis, but all the running gear/drivetrain/everything would have to be modified to a huge extent.

on the other hand, it is certainly possible to make an electric car that goes without all these modifications, its just that there would be no advantages at all. if you want to do it just for the hell of it, go for it i'm behind ya all the way. if you have practical reasons tho, you may want to do a bit more thinking.

pat

patman

iTrader: (3)

compubob, that is a very inefficient design...if you want to do that, just modify the wheels to accept wheel motors, then you have better power, and regenerative braking, plus you have the engine bay open for other stuff, like a hybrid system.

pat

Syonyk

Why couldn't I do regenerative braking on the '7? I do it all the time with my engine... engine braking and regenerative braking are pretty much the same. A gasoline engine just doesn't create gasoline from exhaust.

I'm not doing it for an insanely efficient car... I'd just get an Insight for that. I want something that I can take to the store and back (fairly small town here) reasonably well, without having to cold start a motor every time. If it could beat the pants off a lot of cars, well, so much the better.

As for advantages, I'll just point to the flat torque curve of electric motors. Full torque, right off the line, without having to shift at all. I can see that as an advantage.

-=Russ=-

patman

iTrader: (3)

dude... while i kinda like your idea just because it is weird, you gotta realize that you will never get the same potential for power out of an electric motor as you will from the stock 13B. In my mind there is only one reason for electric cars, and that is efficiency, although if you want to get into it, hydraulic regenerative breaking is better, and then you can use a 'normal' drivetrain.

so...before we talk about this any more, i have one question:

what exactly are your real motives for this? im sure you have some... and i'm srue they are valid, i just want to know what they are.

pat

eriksseven

iTrader: (6)

^ I agree, I still don't quite get the point... Are you really going to do this?

If so, I wonder if there are better sources than the rx7club's 2nd gen tech section...?

About how much are you looking to spend on this project?

Oh, one more thing, is it REALLY worth it? If you want to be economical, get an Insight (like you said). If you want to go fast, get a turbo, or a 13brew or something. If you want a grocery getter... just leave the 7 like it is, or get a Civic or something. If you're really looking for a fast, economical grocery getter.. I think you're having an identity crisis, lol.

Syonyk

I like my cars "different."

Basically, the town I live in is reasonably small (50k people, 7-8 miles diagonal). Most of my driving, when I drive, is very short distances, in the sub-5 mile range. Gasoline engines are horrible at fuel efficiency when cold (try doing a lot of short trips in a '7... they're beyond horrible). An electric car would cover 90% of my driving needs (I bike a lot, but it's hard to get groceries or other people on a bike). As for using an RX-7 chassis, they're fairly cheap (especially with a blown motor), easy to obtain, and, most importantly, I'm familiar with them.

Electric motors have insane low end torque, and are flexible enough that you don't need to shift - one gear suffices.

Pretty much, I'm looking for something to use for short trips, with good performance. An electric car with a range of 40 miles would be more than sufficient for all my in town stuff. If I can mate a sufficiently large electric motor, performance would be fairly impressive as well.

I'm also looking for a project that's within my realm of doable. This certainly is.

-=Russ=-

digitalsolo

iTrader: (2)

Lack of torque? Do you know anythign about electric motors? maximum torque starts at 0 RPM and drops from there (minutely drops). You can pull MASSIVE amounts of torque from a proper electric motor.

I actually considered doing an electric RX7 for my senior design project for EE at Purdue. Ended up going a different direction with my studies however.

I'd love to see this project. A stripped 7 could probably start you at 2300 lbs for the shell, minue engine, WITH an interior in it.

Best luck!

Syonyk

For those who think electric cars are just slow:

http://www.acpropulsion.com/tzero_pages/tzero_home.htm

0-60 in 4.1 seconds, 13.2 second quarter mile.

-=Russ=-