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Discussion Starter #1
Hi all, and thanks a million already for everything I've learned just from poring over the motor, controller, battery and build threads. This place is awesome, and I would definitely not be doing this without this community.

That said: I have a 1992 Mazda Miata I am converting to electric. My goal is: an around-town (limited range) street car conversion that's at least as fun to drive as the (1.6L) stock engine, and preferably a little more fun.

My initial plan is this:

Keep the transmission for safety, stock feel and to be more forgiving on the motor. Previous owner already put in an aluminum flywheel, so I don't intend to modify it further.

Build for 288V. The gearing on the Miata seems deliberately designed around the stock engine, which has a pretty flat torque curve out to 5000 RPM; I don't think a Miata that started to lose power at 3000 RPM would be much fun. In particular, you're already at 3000 RPM in 5th gear at 60 MPH.

Therefore:

Motor: Netgain Warp 11 HV.
This will be a tight squeeze, and may require adjustments to the (manual) steering and subframe, from what I read here.

Battery pack: 60Ah Sinopoly or equivalent, 96-battery pack, serial.
The 3C/5C current rating is key here, plus the geometry of the flatter Sinopoly 60Ah packs in particular fit particularly nicely in the battery trays that EVMiata sells. Others would require more space to achieve 96x60Ah.

Controller: Soliton Jr.
I could put a Soliton 1 here, but I'm not convinced that there will be much benefit; with a 60Ah/5C pack and the 11HV motor I wouldn't be able to put out over 600A past 2500 RPM anyway. And since I'm keeping the transmission, all it would save me is some shifting, and the high amperage would shorten the life of the motor.

I am open to your thoughts and suggestions. This will be a challenging project for me, as I am more of a digital guy than analog or mechanical; however, with the help of local friends and the community here, I hope to get a fun project car working.

Thanks in advance.
 

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be careful with the RPM.

IIRC it's 3000RPM nominal, 5000RPM absolute redline for the warp 11HV.

Edit: 60Ah 3.2V batteries * 96 is 307V, and considering you want a solid 288V under load, you might get mad voltage sag.

Edit2: Inspect the Kostov K11 250V (and the Alpha version) and perhaps dual 9"s as well
 

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In order to use an 11" motor in a miata, the motor/transmission will have to be raised above it's stock position. Being that the car has the torque brace between the trans and rear axle effectively making the complete drive line one piece, just forcing the motor/trans higher will be stressing some mounting points, so keep an eye out for what is being stressed. You may wind up with some type of driveline vibration you didn't have before the conversion. We don't recommend anything bigger than the 9" because of this.
Mike
www.EV-propulsion.com
 

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Hi NJ

I'm sure you have good intention about component choice, but I think you will need to learn a bit more.

I don't see any good reason to use a 230 lbs Warp11HV instead of a 150 lbs Warp 9 because the motor job is only to transform battery energy into rotating power (hp).

Example:

60Ah x 5c = 300A x 288v = 86Kw of peak power (not considering voltage sag)
120Ah x 5c = 600A x 144v = 86Kw of peak power (not considering voltage sag)

So, the battery power capability is your weakest link in both situations.
If you need a short range / high power conversion I suggest you to peek at A123 AMP20 cells.

Finally, using a 1000A controller instead of 600A one that will give you 40% more torque at low rpm (before than the limited battery power became a problem) and that is 40% more power at low rpm.
So, faster acceleration... Not useless!
 

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The 11HV fits nicely in the older Miatas, no frame modifications, clears the steering rack, and there is no noticable vibration. The only downsides I can see are the extra weight over a 9 inch and that you need to remove the motor to get the transmission out.
My understanding is that the 11HV uses the same armature as the 9 inch so the max RPM should be the same.
I agree about the A123's if you want to spend the time to assemble a pack.
 

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Just throwing some options out there.

If you can squeeze the room, evnetics have upped the max voltage to 350v. You can now consider 100 serial (up from 96).
I've considered the best match for Soliton Jr is the Kostov 220v. You should see 220*600 => 132kw. Not far off the Soliton Jr rating of 150kw. This is also a budget friendly combo.
If you want more oomph, then a warp 9 with a Soliton 1 should get to around 160Kw which would be your battery burst limit. (10C burst - 20 to 25% sag this is WAG).
Personally the 11HV or the K11 250v is for a much higher power set up 200 to 300kw+ - For a nice light weight car the Kostov 220v at 45kg sounds nice - cheapish also at ~1700.
 

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Do folks end up having many trans issues in high power converted Miatas? I know in the turbo Miata world the stock trans isn't known for being very strong.
 

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I don't see an 11" motor being a problem for driveline height. It will just barely fit using the stock motor mounts+brackets with a box frame. The more significant limit is fitting behind the front sway bar.

Do you see value in the EVMiata "kit"? It's just a set of simple brackets. Every one needs to be modified to match your components. You'll probably save time by just starting from scratch. The kit omits all of the difficult parts of the conversion.
 

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Discussion Starter #9
Thanks for the quick feedback, everyone.

Just to provide some additional context, I've attached dyno tests for the 1.6l engine currently in the car (sourced from http://blogs.insideline.com/roadtests/2010/04/1994-mazda-mx-5-miata-baseline-dyno-test.html). Add 15% to that to cover the increased weight of the car, and that's my performance goal to meet or exceed.

Keeping the transmission means there is not enough length for a dual series motor setup.

One thing I don't understand is why you would build a 144v x 120Ah pack over a 288v x 60Ah pack. Even if you're targeting a 170V motor, the controller can modulate the pack voltage to the motor's limit, with a corresponding increase in amperage. That would be pretty voltage sag proof, no?

Thanks for the suggestion on the Kostov motors, definitely worth a second look.
 

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Discussion Starter #10
Finally, using a 1000A controller instead of 600A one that will give you 40% more torque at low rpm (before than the limited battery power became a problem) and that is 40% more power at low rpm.
So, faster acceleration... Not useless!
Took me a while with a spreadsheet and the dyno data for the motor to finally understand this -- and, of course, you're right; with a 1000A controller I can put out 1000A even from a 5C/60Ah pack at voltages lower than the maximum. Thank you for pointing this out.

A 600A controller would give me 173 ft-lbs from the motor at the low end, and a 1000A controller would give me 290 ft-lbs. To rochesterricer's note, some of the nicer turbo kits for the Miata are in this range as well; for what it's worth, Flyin' Miata says they have had no reports of transmission issues with their turbo kits but they do say that a stronger clutch is a must.

If I end up with the Kostov motor I can plow the savings into getting the Soliton 1.
 

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One thing I don't understand is why you would build a 144v x 120Ah pack over a 288v x 60Ah pack. Even if you're targeting a 170V motor, the controller can modulate the pack voltage to the motor's limit, with a corresponding increase in amperage. That would be pretty voltage sag proof, no?
You are right!
144v vs 288v was just an example.

But if you target 120-150 hp, I don't see reason to build 288v battery pack.
 

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Discussion Starter #12
Higher voltage, less amperage, less heat in the wires, no? Up to the motor's voltage limit, I mean. It just seems disadvantageous to end up feeding lower voltage to the motor at high RPMs.
 

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Discussion Starter #13
So I emailed the Kostov guys; they hope to have dyno numbers on the Alpha in a couple of weeks. I like the higher (5500 RPM) redline on their 11" motors.

The next best choice seems to be the K9" 220V. I'm still favoring the higher voltage to ensure I have enough torque at higher RPMs at reasonable amperage (~500A). 6800 RPM redline is as good or better than the ICE.

Right now I'm driving the car to get a feel for how it performs with the ICE. The insurance grace period ends in another week, at which time I garage it, file for "non-use" and drop the insurance. Then it's time to pull and sell the engine, not necessarily in that order.
 

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The redline for the 9" motors is 7000rpm, the nominal is 6800rpm. Basically what it means is that if you are feeding it 220v 176 amps and have a 42nm torque load at 6800 rpm it is rated for 31.2kw for an hour.

If you want to push any more than 176 amps through the motor at that speed you need a higher voltage pack than whatever would sag to 220v at 176 amps. From the chart in that other thread your peak torque is at 4500rpm or so unless you are pushing more voltage because the amps start to drop there. I'm not sure what the commutative limits are but 250v was fine according to Plamenator in the other thread but be sure you aren't going to go over 7000rpm. I'm looking to go with 100 cells of 60Ah with a Soliton Jr so that sag won't be an issue, although it's a 20kwh pack of prismatics so some care would need to be taken to be sure that I'm not drawing too heavily against it and getting the battery too hot through heavy discharge but then again I'm looking to convert a 1900 pound aerodynamic car pre-conversion so I'm not too worried, it'll get to 60 fast with a setup like that.
 

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Discussion Starter #15
Prepping to pull the engine at the end of the month. Once that's done I'll attach a mockup of the motor to the transmission and start looking at the fitting issues.

Early specs on the K11 Alpha look pretty good. Integrated forced air gives me a little more confidence about pushing 1000A at low RPMs. I think that's nominal 5800 RPM I see on the site? If so, that seems pretty reasonable; that would be ~100 MPH in 5th. K9 220V is a very decent fallback if the mechanical issues of the 11" motor prove more hassle than they're worth. I'm curious as much as anything else at this point; I may still choose the smaller motor in the end.

This thread needs some pics soon. So far nothing to show that doesn't look like a stock Miata.
 

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Discussion Starter #16
Compression checked the motor... not perfect (210/180/180/210), but not bad for a 20-year-old engine with 145k miles. Looking around for a buyer on the Miata forums.

Received the Warp 11" mockup from EV Source. Once we have the engine out we can reassemble this with the transmission and do a test fit. I want to be absolutely sure the larger motor is going to work. If I end up with the Kostov 11" motor I'll have an extra .2" of clearance on both sides, but I'm hoping it won't be *that* snug a fit.

Also received the hub and adapter plate. Kerryman, if you're watching, cancel your order and get one from EV Source/CanEV instead... mine arrived in about two weeks from the order date.

Next weekend: drain, disconnect and pull engine.

FWIW, the EVMiata folks just hired a new welder, so my kit may have some delays. The part I really need first is the motor mount.

To DJBecker's point: the EVMiata kit has already saved me time in the planning stages, since it lets me predict how many batteries I can fit, and where; and it takes most of the welding out of the build, which is not my strong suit. Plus, those guys have been very supportive and answered lots of my questions, both through their step-by-step instructions and many emails.
 

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Discussion Starter #17
Well, seven hours later, my friend Andy and I wrestled the engine out of the car. Getting at some of the transmission bolts was... amusing.

CIMG0248s.jpg
Andy brings his heavy equipment.

CIMG0251s.jpg
Catching the wild 1.6L ICE.

Next step is to transfer the flywheel/clutch/plate to the 11" motor mockup and see what it will take to fit it. It's pretty clear it will hit the steering rack first, so that'll be the thing to look at.
 

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You didn't pull the motor and transmission out still joined? It would have been easier that way. You'll eventually need to pull the transmission out anyway.
 

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Discussion Starter #19
Transmission stays, at least as far as the EVMiata manual says. Once the hub and adapter plate are on the motor, I mount it and bolt it back on.

Light progress in the last couple of weeks. Took the clutch/plate and flywheel off the engine:

CIMG0252m.jpg

... and drained the gas tank. Every set of instructions said to loosen the drain plug until your arm is soaked in gasoline, and they were right. A gallon and change later and I put it back in. Have to figure out a clean way to fill the tank with soapy water (siphon, probably) so that I don't set any remaining fumes on fire with the plasma cutter later.
 
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