Hello from Michelle :)

[Lady Bhaal]

Hello.

I've got this crazy plan to get a 1993-1999 MR2 and make it electric

So far I plan on attaching this:
http://www.automation.siemens.com/ld...5135-4ws28.pdf
engine directly to the rear differential and put these these tyres on:
Front: 205/45ZR16
Rear: 215/40ZR17
The diameters are max 0.4% different from stock 15" rims

At 120km/h I'll be doing ~5000rpm on the motor, at which point torque is down slightly, max torque is down by 1/2, but power and max power are maxed. The motor is good for 10000rpm.

My main question is: will the rear diff handle the motor? Max torque is 450Nm
A secondary question is: is this even sensible?

[chackoc]

Don't know the first thing about what you're trying to do, but whether you manage to succeed or not it would be fantastic if you could write up how you went about it. I got my NA MR2 to save on gas and converting it to all electric would be pretty much my ideal setup.

[shimric]

Anything is possible with the right amount of $$$$ and time. I'd be interesting to see non the less. Good luck and welcome.

BTW: If you live in North America, you'll only be getting 91-95. Good luck finding a 95 and if you do you'll be paying more than a pretty penny. Best thing to do IMO would be to butcher a 91.

[nitrambb]

Hi and welcome to the board. imho your plan is only crazy if the cost exceeds the resulting benefits. Have you thought through where you’re going to fit the batteries, how long they'll take to recharge, and range on single charge? From what I've read these have been the main reason why there aren't more all electric autos available today. That's after @ 30-50 years of research into their development.

Bob

(if cost isn't a limit, even a rock can be made to fly.
look at the glide slope for a Phantom II)

[chackoc]

Don't know if it would be of any help but this is a bike conversion someone did. I imagine the bike is a lot easier because of the lower weight.

How to build a 72Volt electric motorcycle

Also, I think one of the main reasons it hasn't been successful commercially is because consumers don't want to buy a car that can only go 30 or 40 miles on a charge. Doing so means having to have some sort of alternate arrangement for longer trips. So the big automakers have to focus on cars that go significantly further on a single charge (or include some kind of secondary power source to extend range.)

I have to think that someone who is building their own understands this and is willing to accept the shorter range limits. If so, they have a much lower bar to reach than commercial manufacturers.

[muffinman]

Welcome

I've been trying to figure out a way to do the same thing but with an MK1 , check out this one: Brian's Electric MR2!.

If you decide to do it please post pics.

[curvesrgood]

We've got an electric mk1 local here... actually it is a local college's race car! I think it is only good for short stints, but very interesting, and they had a nice setup. I've been keeping an eye out for it again, but haven't seen it lately. I wanted to take pictures to share it with everyone! Good luck to you, but the conversion will definately cost a bit. The mk1 racer had quite a bank of batteries, and was totally stripped of course.

[Lady Bhaal]

nitrambb: Yes, I have thought about those things. If I can't get 3Phase power it'll take about 6-8 hours to charge the main battery pack, so that's not really practical. However that's an option for overnight charging, just not during the day. Yes, I've thought about where I'm going to fit the batteries, and I'm going for a small-ish battery pack. The main advantage I have here, is as chackoc said, is that I'm not trying to build a commercial car, just something to get me around during the day.

Also, this won't be purely electric As noted, that's just not practical for a 'normal' use car yet. This will be a serial hybrid. I plan on putting a small diesel generator into the space where the petrol tank used to be, which will be used purely to charge the batteries. The batteries are long term storage, and also power the car's internal electrics (lights, gauges, and so on) The batteries connect to a set of ultracapacitors which drive the engine. This gets me the acceleration and regenerative braking capabilities I want, without the HUGE battery pack that that current flow would require. The generator gets me the range that I don't get without the HUGE battery pack, and also means that if I run out of power, I can just pull up to a servo and refuel, I'm not totally stuck.

Shimric: I'm not in USA, I'm in Australia

Chackoc: If I do this, I'll document and photograph everything

I won't be using lead acids, they're far too bulky and don't hold enough power. Instead I plan on using these:
http://www.kokam.com/product/product...40Ah_Grade.pdf

Now: Where should I ask the following questions:
What are the specs for the 1993-1999 Rear Differential/Axle? Can it handle 450Nm of torque? If not; what's a good replacement?

[muffinman]

Originally Posted by Lady Bhaal

I won't be using lead acids, they're far too bulky and don't hold enough power. Instead I plan on using these:
http://www.kokam.com/product/product...40Ah_Grade.pdf

obviously the less weight the better but the link was to show an example.

lithium would be the best way to go.

[Lady Bhaal]

Definitely The Kokam's are LiFePo's

[muffinman]

what exactly is 450Nm in ft.lbs?

[chackoc]

332 ft-lbs based on the first online calculator I could find.

[chackoc]

Does the use of capacitors mean if you're accelerating for a while the capacitors could fully discharge and you'll suddenly slow down to whatever the batteries can provide directly?

If so do you know how long it might take to fully discharge them at WOT? Does ultracapacitor mean it has an abnormally high capacity? Also, if it would be a pretty rapid loss of acceleration when the capacitors fully discharge do you have a feel for how much speed you'll lose when/if it occurs? I'm not really talking about racing, but if you're on merging onto a highway it would be terrible to be building up speed to match traffic only to suddenly lose half your power.

Just curious about the dynamics of the whole thing.

[Lady Bhaal]

chackok: yes, you are correct, all the high current comes from the ultracaps, but it's worse than you suspect. At speed the ultracaps would have to be mostly empty, as they need to have enough spare capacity to recover all the energy from a full regenerative stop. I haven't done the full maths yet, but I know that it's something I need to consider. I'm aiming to always have a spare 10 seconds of full acceleration just in case, hopefully that will be enough.

Now, why is nobody answering my questions on the rear diff?

[chackoc]

I've only been on these board for a bit I haven't seen many people talking about running 330+ lb-ft. There might not be many people who could answer with any certainty.

You might have better luck if the post he question again in one of the other forums. Maybe the autox forum, or even just general discussion.

[Lady Bhaal]

My main question was where I should ask those questions. Thanks, I'll try those places

[RedAuzBathurst94]

Welcome, nice to see another aussie Actually im sure i saw an electric mr2
sw20 for sale about 8 months ago somewhere in queensland...

[Mark_Dorman]

The turbo differential should handle that just fine. I've seen turbos running higher numbers than that. I doubt the NA diff would though...

[Lady Bhaal]

Thanks for that Now to find a turbo MR2 with good body but a broken engine

[Mark_Dorman]

Glad I could help...you could always get a hold of a turbo tranny and put it into a NA. Probably easier to just find the turbo model like you said though. You can always buy one with a good motor and sell the engine. I know there is a decent market for 3sgte's most places.

I'm really interested to see how your project goes. I've been planning to do a v6 swap for a while but this has really sparked my interest. Keep us posted