# Time to fish or cut bait ... '92 Miata conversion



## DC Braveheart (Oct 12, 2008)

OK - I'm ready to dive in. After months of reading blogs on the internet and following the numerous threads in this forum (which IMHO is one of the best resources on the internet on any subject) I'm ready to start converting my '92 Miata. 

Converting to what is another matter. I'm torn between 2 basic choices - AC or DC. If I go AC I plan a 320V system using an Azure Dynamic AC24LS and 60aH TS Lifepo4 cells. If I go DC, I'll use a Warp9 with a Curtis 144V controller and 160aH TS cells. I'll use ElectroAuto's AC/DC kits and source the TS cells from Jungle Motors. For BMS I am still looking for options, but Brian Blocher's cell balancer's look like a must-buy.

I'm not kidding myself that I have the technical know-how to do this without some help - from what I've seen on this forum I'm hoping (expecting) that some of you will be coming to my rescue at some time or another!

Any comments you habve on the choices above would be most appreciated. 

I'll document the conversion on a blog here: http://e-miata.blogspot.com and cross-post here if there is interest in what I'm doing.

Thanks,
Stuart


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## bblocher (Jul 30, 2008)

Glad to hear you are jumping in. It's such a fun experience. You're going down the right path with lithium, especially for a little car like that.

I keep telling myself I wish I would have went with an even more powerful AC setup, but that's really it. Any of the obtainable/affordable AC setups don't have crazy performance differences compared to the DC setups (at least looking at the performance specs). One thing to keep in mind is finding all the other components you'll need that can run off 300+ volts. You will be more limited there for sure. You'll also have that many more lithium cells to monitor and balance. A plus side, however, might be finding more places to fit all those cells since they are smaller. It was a real challenge fitting all the 160s in my car. We'll that's half true, I still have all the space the gas tank use to be but I wanted easy access without cutting a large hole in my trunk.

Don't worry about feeling like you are in over your head when starting. I felt the same way. A little patience to learn and as you mentioned some help from a lot of people here wanting to see you complete the job.

Best of luck, I'll be following the blog!


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## DC Braveheart (Oct 12, 2008)

bblocher said:


> Glad to hear you are jumping in. It's such a fun experience. You're going down the right path with lithium, especially for a little car like that.
> 
> I keep telling myself I wish I would have went with an even more powerful AC setup, but that's really it. Any of the obtainable/affordable AC setups don't have crazy performance differences compared to the DC setups (at least looking at the performance specs). One thing to keep in mind is finding all the other components you'll need that can run off 300+ volts. You will be more limited there for sure. You'll also have that many more lithium cells to monitor and balance. A plus side, however, might be finding more places to fit all those cells since they are smaller. It was a real challenge fitting all the 160s in my car. We'll that's half true, I still have all the space the gas tank use to be but I wanted easy access without cutting a large hole in my trunk.
> 
> ...


Thanks. The points you made are part of the reason I've still not decided which way to go AC vs DC. I plan on getting the ICE out, opening up the gas tank area and the trunk area behind it and then seeing how many cells I can get in. The 60aH cells are just a little over half the size (in terms of surface area) than the 160aHs so I'm optimistic that I can fit 100 60aHs where others have managed to fit 50 of the 160Ahs. I'm in no real rush to finish (like I say in my blog, this is going to be a project that expect to be an excape from real life ... if it goes too quickly I'll soon have to find something else to do).

The AC motor from Azure is a bit weak and that might be the final tipping point to going the DC route. I've yet to find another AC Motor/Controller package that is moe powerful yet not prohibitively expensive (like the ones available at MetricMind) and while I'm not too concerned about the cost, I'm certainly not going to drop the amount of money that would take into this. 

Stuart


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## dimitri (May 16, 2008)

Well, I gotta sign up for this one  . Can't miss a Miata build...

I can't add much to what Brian has said except one thing. You can still do DC and use small cells, just wire them in parallel-serial config. I was contemplating to use 60Ah cells, but couldn't decide between 2P or 3P config. 2P ( 2 cells in parallel ) seems a bit small, but 3P seems a bit expensive, in the end 160Ah turned out perfect for me, but I would still recommend to think about 2P or 3P if you have room for smaller cells, but not for larger cells, its a good option to have up your sleeve. 

I personally don't see a point of going AC until it becomes price competitive with similar size DC setup. 

I've driven 144V DC Miata with 1000Lb of lead and it was a "ton of fun" pun intended . I can only imagine how cool it would ride with Lithium batts.

BTW, where are you located?

Good luck with the project! Hope we can help with advise!


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## DC Braveheart (Oct 12, 2008)

dimitri said:


> Well, I gotta sign up for this one  . Can't miss a Miata build...
> 
> I can't add much to what Brian has said except one thing. You can still do DC and use small cells, just wire them in parallel-serial config. I was contemplating to use 60Ah cells, but couldn't decide between 2P or 3P config. 2P ( 2 cells in parallel ) seems a bit small, but 3P seems a bit expensive, in the end 160Ah turned out perfect for me, but I would still recommend to think about 2P or 3P if you have room for smaller cells, but not for larger cells, its a good option to have up your sleeve.
> 
> ...


Dimitri,

Yours was one of the builds that inspired me to do this - shame you let that car go - it looked great. Love what you're doing with the Protoge5 (you'll see the one I bought for my daughter in the background of the pictures on my blog - I've also got a CX-7 - love Mazdas!).

Thanks for the input - I'll certainly bear it in mind as I make my decision. That might happen a bit quicker that I expected. It took less than 12 hours for me to sell the engine on Craigslist - I guess asking $300 for an engine with only 78,500 on it was too little! 

I'm located a bit further north than you - in Herndon, Virginia. I'll definitely have to invest in a heater up here AND I'll need to retain the A/C. Currently I drive this car in all weather from 20F to 100F+ (with the top down of course!) - gonna need both if I'm gong to continue doing that.

Stuart


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## speculawyer (Feb 10, 2009)

I assume you've looked at the Miata converted by the Elite Power Systems person:
http://evworld.com/article.cfm?storyid=1643

http://elitepowersolutions.com/products/news.php?article=1


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## DC Braveheart (Oct 12, 2008)

speculawyer said:


> I assume you've looked at the Miata converted by the Elite Power Systems person:
> http://evworld.com/article.cfm?storyid=1643
> 
> http://elitepowersolutions.com/products/news.php?article=1


Cool - that was not one I had seen before. Nice range they got using the 200aH TS cells - certainly implies that 100 miles is achievable with the 160aH's (not that I need that kind of range).


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## RKM (Jun 9, 2008)

Braveheart,

Great news that you're going ahead with your Miata conversion!

I'm just a small step ahead of you (engine and ICE related stuff removed, adapter and coupler made). I chose DC for cost and performance for the money. Take a look at Belktronix package and the Cycle Analyst for monitoring. My project is parked for about six weeks while I get caught up on some work. Plan to go at it hard in May and June.

Are you interested in the Sky Energy group purchase that Techno has been researching?

Will be watching.

Rob


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## DC Braveheart (Oct 12, 2008)

RKM said:


> Braveheart,
> 
> Great news that you're going ahead with your Miata conversion!
> 
> ...


Rob,

I have no doubt you'll stay well ahead of me - especially with that rotisserie! Thanks for the tips - I'll look into those.

On the cells it will depend on timing. I do like the price Technologic has found but like others have mentioned I think I'd prefer the security (possibly false security) of having a supplier in the States standing behind a purchase that will be north of $10K.

Stuart


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## DC Braveheart (Oct 12, 2008)

Well today I officially got started and began pulling ICE components out. I removed:

- the engine and transmission oil
- the coolant (well some? of it - question for Miata buffs below)
- air intake system
- alternator
- engine splash shield
- radiator fans

Not too much for the first day, but I was initially stymied by an oil drain plug that must have previously been (over) tightened by an impact wrench. Damn thing refused to budge for ages until I finally resorted to using my foot on the wrench ... just picture that!

I would have taken out the radiator too but I'm concerned I have not got all the coolant out. I got just over a gallon and the Haynes manual says there are over 6 quarts of capacity. It also says that there is an engine block coolant drain on the "side of the engine block" - but I'll be amned if I can see anything that looks like the picture in the Haynes manual. so for you Miata enthusiasts out there - any idea:

- if I've got all the coolant out or
- if I'm just blind

If the latter - can you point me to the position of that engine block coolant drain?

Stuart


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## tj4fa (May 25, 2008)

DC Braveheart said:


> If the latter - can you point me to the position of that engine block coolant drain?
> 
> Stuart


Seems like you're not the only one wondering how to drain all the coolant out.

http://groups.google.com/group/rec.autos.makers.mazda.miata/browse_thread/thread/fe3285653b969e0c


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## DC Braveheart (Oct 12, 2008)

tj4fa said:


> Seems like you're not the only one wondering how to drain all the coolant out.
> 
> http://groups.google.com/group/rec.autos.makers.mazda.miata/browse_thread/thread/fe3285653b969e0c


Thanks - I'm glad to see that there are people out there more confused than me. I guess if it don't find an answer that worst that happens is that I need to clean up less than 2 quarts coolant when the engine comes out.


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## DC Braveheart (Oct 12, 2008)

I'll update the blog at http://e-miata.blogspot.com when I recover ... but as a quick update ... the ICE is OUT!


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## tj4fa (May 25, 2008)

That's gonna be a sweet ride when you're done!

Here is a link to a fairly active Mazda Miata Forum where you may be able to sell off some of your old ICE stuff and recoup some of your expenses.

Maybe even get a few parts if you need them.

http://forum.miata.net/vb/index.php?


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## DC Braveheart (Oct 12, 2008)

tj4fa said:


> That's gonna be a sweet ride when you're done!
> 
> Here is a link to a fairly active Mazda Miata Forum where you may be able to sell off some of your old ICE stuff and recoup some of your expenses.
> 
> ...


Thanks! I've already sold the major component - I put the engine up for sale on Craigslist a couple of weeks back - I had 4 offers and it was gone within 12 hours! Once I've finished pulling the rest of the ICE stuff I'll probably list it there. I'll probably join that forum and post a link to the Craigslist listing too, so thanks for the pointer. I'll definitely check it out for any replacement parts I need.


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## JRP3 (Mar 7, 2008)

I don't know if you've made a motor choice yet but the AC31 HPG motor is similar in performance to the Solectria AC24 but a lot cheaper and runs on lower voltage. The AC31 has more torque than the AC24 but doesn't rev as high.
http://www.diyelectriccar.com/forums/showthread.php/new-ac-motor-available-24498.html


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## DC Braveheart (Oct 12, 2008)

JRP3 said:


> I don't know if you've made a motor choice yet but the AC31 HPG motor is similar in performance to the Solectria AC24 but a lot cheaper and runs on lower voltage. The AC31 has more torque than the AC24 but doesn't rev as high.
> http://www.diyelectriccar.com/forums/showthread.php/new-ac-motor-available-24498.html


Yeah I looked at that whe the thread was started. I'm still debating whyc way to go on the motor but in my mind one of the main reasons for going AC is so that I can use a (much) higher voltage. Since losses due to resistance are proportional to the square of the current, doubling my voltage with a HV AC system will mean half the current flow and so a quarter of the losses. 

What will make my mind up ais when I've finished disassembly and figured out exactly how many TS cells I can fit in - if I can manage 100 60AH cells I'll go 320V AC, if not, then I'll use 45 160AH cells and go DC ... maybe  ...


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## DC Braveheart (Oct 12, 2008)

My ICE was picked up today ... I guess I can't turn back now!


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## DC Braveheart (Oct 12, 2008)

More stuff out this weekend - I dropped the rear subframe and removed the gas tank. But the highlight of the weekend was a ride in a Tesla Roadster. You can find details in my build log here:

- http://e-miata.blogspot.com/2009/04/exhausting-day.html
- http://e-miata.blogspot.com/2009/04/ev-inspiration.html
- http://e-miata.blogspot.com/2009/04/subframe-and-gas-tank-out.html


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## EV-propulsion.com (Jun 1, 2009)

We have made a miata kit available and have pictures of our real clean conversion at www.EV-propulsion.com 
We chose Dc and lead for several reasons, one we wanted to be able to do miata conversions for around 20K, plus our geographic location doesn't require long range. Of course alternate batteries, etc are optional. On this conversion we used optimas, maybe not as good as odessys as far as lead goes but cost effective for this particular cars intended purpose and still pure lead,not lead calcium.
Individual parts are available too.
Mike


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## DC Braveheart (Oct 12, 2008)

EV-propulsion.com said:


> We have made a miata kit available and have pictures of our real clean conversion at www.EV-propulsion.com
> We chose Dc and lead for several reasons, one we wanted to be able to do miata conversions for around 20K, plus our geographic location doesn't require long range. Of course alternate batteries, etc are optional. On this conversion we used optimas, maybe not as good as odessys as far as lead goes but cost effective for this particular cars intended purpose and still pure lead,not lead calcium.
> Individual parts are available too.
> Mike


Mike,

Cool. I'll be in touch shortly ... while I have all the major electric components on order (in process of shipping), I'm still looking for some of the hardware components - specifically motor mount and coupler. Yours looks really interesting as it appears to allow re-use of the stock A/C compressor.


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## EV-propulsion.com (Jun 1, 2009)

Hi DC,
The available parts are designed around a warp9 motor. I didn't see in your blog if that is what you decided on yet. But if you did I can set you up with any parts you may need. yes the stock a/c compressor can be used and also P/S if you have it. I am making some improvements to the brackets, so there will be a few week (4-6) delay in shipping out.
Mike


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## DC Braveheart (Oct 12, 2008)

Long time - no post ... I've been slowly accumulating parts and finally found time this weekend to get back to work on the car having received my transmission adaptor on Friday. 

The coupler I received with the kit fits fine but the bolts that hold the adaptor plate and motor spacer to my Warp9 interfere with the flywheel - if I remove the lock washers the bolt heads just clear - the lock washers are 3/16" thick. 

Has anyone else out there who either created their own adaptor or purchased one for a Miata had a similar issue? I figure that to get the correct "magic number" (the distance from the rearmost surface to the ICE to the rearmost face of the flywheel) that the space between the flywheel and adapter plate is also fixed. This appears to be about 0.25" which does not seem enough for a standard bolt + lock washer combo. What have you done (recessed the bolt heads in the adapter plate? shaved the flywheel)?

Thanks!


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## evlowrider (Jul 23, 2009)

DC Braveheart said:


> Has anyone else out there who either created their own adaptor or purchased one for a Miata had a similar issue? I figure that to get the correct "magic number" (the distance from the rearmost surface to the ICE to the rearmost face of the flywheel) that the space between the flywheel and adapter plate is also fixed. This appears to be about 0.25" which does not seem enough for a standard bolt + lock washer combo. What have you done (recessed the bolt heads in the adapter plate? shaved the flywheel)?
> 
> Thanks!


Hi there,

I haven't fitted my adapter yet, here is a pic of mine for my MX5 Miata. Note that the holes for the motor bolts are recessed on mine (there is 2 different bolt patterns on mine for 8" or 9" motors I believe).











I got this from Electric Vehicle Solutions.

Pete.


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## Tesseract (Sep 27, 2008)

DC Braveheart said:


> ...The coupler I received with the kit fits fine but the bolts that hold the adaptor plate and motor spacer to my Warp9 interfere with the flywheel - if I remove the lock washers the bolt heads just clear - the lock washers are 3/16" thick. ...


Try internal tooth lockwashers instead of split-ring, and use Loctite on the bolts to make up for the lower effective locking force.


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## DC Braveheart (Oct 12, 2008)

evlowrider said:


> Hi there,
> 
> I haven't fitted my adapter yet, here is a pic of mine for my MX5 Miata. Note that the holes for the motor bolts are recessed on mine (there is 2 different bolt patterns on mine for 8" or 9" motors I believe).
> 
> ...


Pete,

Thanks - that's great info.


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## DC Braveheart (Oct 12, 2008)

Tesseract said:


> Try internal tooth lockwashers instead of split-ring, and use Loctite on the bolts to make up for the lower effective locking force.


Tesseract,

Thanks. I think even with thinner lockwashers as you suggest there is insufficient room as without any the bolt heads barely clear the flywheel. I'm getting some new bolts with thinner heads - so I may go with your idea, but I may end up sending the plate back to get the bolt holes recessed as Pete suggests above.

Thanks!


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## Tesseract (Sep 27, 2008)

DC Braveheart said:


> ...I think even with thinner lockwashers as you suggest there is insufficient room...


Hmmm... Okay, if the bolts that came with the plate are either hex head or socket head cap screws then switching to button head will gain you quite a bit of clearance, too.


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## DC Braveheart (Oct 12, 2008)

Got my bolt problem sorted. The adaptor supplier was very helpful in sending some low profile-head bolts and some locktite but I decided to go ahead and get the 'rear' ring on my flywheel shaved down to the level of the ring gear anyway and that provides plenty of clearance for the original bolts and lockwashers (and combined with removing the ring gear, a lighter flywheel into the bargain!)


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## evlowrider (Jul 23, 2009)

Hey,

I'm wondering what are your plans for your motor mount? I'm trying to figure out what to do for my MX5 Miata at the moment.


Cheers,
Pete.


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## RKM (Jun 9, 2008)

Pete,

I've taken the clam shell approach used by most for the motor mount. I've bolted to the original motor mount location. The photos are of my MX-5.

Rob


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## DC Braveheart (Oct 12, 2008)

evlowrider said:


> Hey,
> 
> I'm wondering what are your plans for your motor mount? I'm trying to figure out what to do for my MX5 Miata at the moment.
> 
> ...


Pete,

I got mine from the same supplier as the adaptor - http://www.ev-propulsion.com/kits.html - it was not cheap but I'm pretty impressed with the quality ... though I've not installed it yet. Rob's (posted above) looks great ... maybe you can convince him to build one of his for you!


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## DC Braveheart (Oct 12, 2008)

I ran up my motor for the first time yesterday - the only 12V battery I had to hand was my Miata's ... boy does it's voltage sag when trying to spin up a WarP9! 

With my newly lightened flywheel attached the motor spun uo and then started to wobble - blast! The shop that lightened it said that it should have remained neutrally balanced with the removal of the ring gear and shaving the back ring off it. I guess they were wrong.

I pulled it off the motor, slid it onto the input shaft of my tranny and gave it a spin. Using a plumb-bob I marked the lowest point when it stopped and then spun in the opposite direction ... it stopped again in almost the same place. Hmmmm ... I moved that point to 3 o'clock and let go ... it slid back to the bottom. Repeated at 9 o'clock and same thing. So I guess I've found the heavy point. 

Messing around with a few different sized washers I was able to even it out. Maybe I'll try this again with the clutch pressure plate attached and see if I can balance the entire assembly with some washers under the pressure plate bolts. Failing that I guess it's back to the machine shop.


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## DC Braveheart (Oct 12, 2008)

Ooops - another issue that need addressed. While I was taking the flywheel off the motor I noticed that there was some free play between it and the coupler. I e-mailed the supplier who went to check and it turns out the the coupler was machined a little smaller then the original ICE crankshaft end that fits into a space in the flywheel. As a result, it's not possible to exactly center the flywheel on the coupler (and even if I did somehow manage to, it would eventually move out of true again). He's going to get a new one of the correct size machined for me (can't complain about that kind of service).

In the meantime, I think I'll take the flywheel back the the machine shop for balancing. With the clutch pressure plate installed the entire assemble is still unbalanced and the light point (where I'd add weight to balance it out) is between 2 of the bolts holding the pressure plate to the flywheel. That means I'd have to add washers to both bolts to try to even things out ... I think I'll leave it to someone who knows what he's doing.


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## EliteEV (May 6, 2008)

DC Braveheart said:


> In the meantime, I think I'll take the flywheel back the the machine shop for balancing... I think I'll leave it to someone who knows what he's doing.


You are doing exactly the right thing, DC! I know because I didn't. Before installing my motor/transmission I noted a little vibration on 12V but thought nothing of it. After installation and test drive I found it was really bad at ~3000 RPM. Out with the batteries, racks, electronics, and motor, then to three different machine shops before I found one that did the job right. I ended up getting the coupler and flywheel remilled and those and the pressure plate balanced together. Now it's nice and smooth! Good luck with the rest of the build...you are in for a lot more fun!

Scott
http://www.diyelectriccar.com/garage/cars/123


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## DC Braveheart (Oct 12, 2008)

EliteEV said:


> You are doing exactly the right thing, DC! I know because I didn't. Before installing my motor/transmission I noted a little vibration on 12V but thought nothing of it. After installation and test drive I found it was really bad at ~3000 RPM. Out with the batteries, racks, electronics, and motor, then to three different machine shops before I found one that did the job right. I ended up getting the coupler and flywheel remilled and those and the pressure plate balanced together. Now it's nice and smooth! Good luck with the rest of the build...you are in for a lot more fun!
> 
> Scott
> http://www.diyelectriccar.com/garage/cars/123


Scott,

Thanks for the feedback. Nice car you got there!


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