[SolarJ]

I have a 1990 Mazda Miata which I will install a AC55 with 104 - 60 AH LI and direct drive. She will be named MX-AC55. If anyone is interested I will post the build thread here. This will be a direct drive motor with a ratio of 4.3:1 and a final weight of 2400 lbs she is 2300 now. This is what I am hoping to get out of it: 60 Miles of range at 50 mph. Top speed around 80. 0-60 about the same as the orig. 9 sec. Handling is also very important so the weight balance needs to be identical at 50:50. I already have all the ICE components out of the car. Wow that gas tank space is tight. What's next? I need to weigh the car after its all out to detirmine the how much its growing, and plan possible component placement.

Has anyone else tried this setup? I didn't see any out there. Many thanks to all who have come before me who put the idea in my head

- Jim

[etischer]

Without running the numbers, a 9 second 0-60 direct drive seems a bit optimistic to me. The ratio you want to use would be like starting the car in 4th gear, I don't think it will work well. It is possible to go direct drive, but not with the 4.3:1

I've always been curious to see some of these AC55's in use, there aren't many small cars on evalbum that use them.

[evlowrider]

I'll be following your build thread. I don't have any experience with AC-55 so I don't have anything to say on that front. I'm converting an MX5 aswell, however its DC with a Warp9 motor.

Good luck on your build.

Pete.

[Stunt Driver]

Definitely post build news here, and add to garage as well.
Community is growing!
Where are you geographically?
What is your budget?

[RKM]

Jim,

My Miata conversion is all but complete, at the paint shop now (Warp 9, Belktronix stuff, 800A controller, 144V TS 180Ah, clutchless). I need to take a post conversion weight, but am estimating a gain of 350 pounds.

It's been a long time since I've looked at the specs for the AC55. As I recall, its large and heavy. The Warp 9 is tight in the Miata, moreso for diameter than length. You've checked that you have space to the AC55? Oops, forgot, you plan to direct drive. That changes everything. You'll likely be able to move the motor into the tunnel a bit.

I suspect etischer is right about the acceleration. You would need huge torque (massive amps) to accelerate briskly with that ratio. I know you're using high voltage but I suspect the bottom end acceleration will feel a bit soft. I may be wrong, frequently am.

Getting to be lots of Miata conversions out there. Good luck, have fun.

Rob

[CroDriver]

I wouldn't recommend direct drive with a AC55 since the power output decreases rapidly with rising RPM...



You need 4X more power to double your speed. If the power is decreasing while speed is rising you won't go very fast...

[dimitri]

Why is there such obsession with direct drive? What do you gain vs. what you loose? You eliminate 40-50 lb transmission, but you picked a motor that weighs 100 lb more than comparable DC Warp. You eliminate few percentage of mechanical losses, but you waste tons of precious amps during acceleration, while killing your battery in the process. People assume that electric motors have tons of torque and that is a ticket to direct drive, but all that torque comes at the price of huge amps, heat losses, battery losses, etc.

Sorry, but I just don't get it......

SolarJ, this was not against you personally, it just seems to be a common theme lately.

I converted Miata and let me tell you, if I was to lock it in 3rd gear, it would suck big time, it would be an embarassment to drive. I'm sure some will come here and argue that they drive in one gear, but they don't go 80 mph and 0-60 in 9 sec all in one gear, and if they say they do, then they are big fat liars . Oh, and they don't get 60 miles range in one gear, not with 16kWh usable pack energy.

Please calculate all details before you jump into direct drive, or wait for Brian to finish his Kia with same exact motor and direct drive and see how it turns out. Some posts in Brian's thread talk about compromises of direct drive, such as picking either acceleration or top speed, but not both.

Hope this helps.

[EV-propulsion.com]

I agree that the gear ratio isn't low enough (higher numerically). It will be tough to get that acelleration and top speed of 80 you desire. If I remember right, the max rpm of that motor is 5000 to 5500 which is limiting how much you can gear down and still have a high top speed. Why not at least gear it down for acelleration, and make the top speed 55-60. I personally would use the transmission.
I also agree that if you do use the transmission there may be a clearance problem with the crossmember. For proper driveline angularity (with trans), a 9" motor is very close to the frame, that large diameter ac55 probably wouldn't fit without possibly removing some of the cooling fins? or more?
If you use the gas tank area for batteries, there is approximately 9.5 inches between the doghouse (the gas tank area behind the seats) and the rear axle supporting structure so be sure to check your battery dimensions (unless you will be raising the doghouse)
For some pictures of this gas tank area on our site see
http://www.ev-propulsion.com/projects.html
And yes its starting to look like the miata is the #1 conversion car....
Mike
www.EV-propulsion.com

[etischer]

400A @ 312VDC is 125kw, but the graph shows a peak of only 60kw.

Their data sheet states max current is 250A @ 312v, I think this is the correct number to acheive 60kw.

Originally Posted by CroDriver

You need 4X more power to double your speed. If the power is decreasing while speed is rising you won't go very fast...

[SolarJ]

Wow where do I start. I am in the Seattle area. My budget for the project is 17K and I am off to a great start on the budget since I planned for orig car cost of $3000. I picked up a 90 Miata with a bad engine for $900.

If the car needs a tranny after I try out the direct drive, Then I will figure out a way to get it in there or go with a Warp 9 and use this AC-55 for a different project.

This motor is huge and should not have any problems driving this little car.

Also it looks like at least half of it will be able to fit into the tunnel. Good News

Thanks, Jim