[mshobe]

Hello all,

Been lurking a bit and like so many before me, I now have a passionate goal to turn a good ICE-powered vehicle into a great EV. My goal is to exceed the book performance of my current '96 Miata M Edition 0-60 (target sub-6 seconds), while maintaining a modest range goal of 50-75 miles of "normal" driving. Other considerations:

• AC motor with regen
• Use existing transmission
• strive for 50/50 weight distribution, front-and-rear
• no need for A/C, but performance braking and suspension are desirable

I have scoured EV West's product listings and something like their 818 Kit as starting point makes sense, but perhaps with a Dual motor like this - to get closer to the original ICE power output?

I've seen some of the other Miata threads and it looks like a lot of custom fabrication for battery placement and motor mounting is ahead of me, and I'm also unsure of exactly what sort of adapter plating I need to cook up to mate the motor to the stock transmission. I'm also unsure about how to drive the existing 12V system from the new battery pack, and how best to fire up a performance brake system. Let the learning journey begin!

 

[Kevin Sharpe]

I now have a passionate goal to turn a good ICE-powered vehicle into a great EV.

Welcome to the forum

Can you tell us what your budget is for parts? Also whether you'll be doing the work yourself or paying someone else? This has a huge impact on the solutions that we propose

 

[mshobe]

Sure thing - sorry for the obvious FAQ misses on my part. I look forward to help + advice!

Let's call the total electric powertain acquisition, mounting and adaptation budget $15K, and labor set to just engine removal by a qualified shop - the rest is meant to be totally DIY. Fortunately I have access to an excellent DIY garage here in Seattle (theshopclubs.com) and mechanic consultation as part of that membership.

Now, since the Curtis 1238e-7621 HPEVS Dual AC-34 Brushless Motor Kit - 96 Volt dual motor I originally linked to is, itself, $7900, that $15K is going to get near the limit fairly quickly with too many mistakes if that's the power level I'm going for. I also mentioned EV West's 818 kit as a very rough punch list but with something stronger than an AC-50 as the motor.

 

[Moltenmetal]

Hi and welcome-

If you can afford the dual motor, it'll be easier than Frankensteining an OEM EV transaxle into the car.

Assuming you re-purpose OEM batteries from a Leaf or Volt or Tesla etc., you should be able to stay within your budget- depending on your range goal that is.

Best of luck- an electric Miata will give you a serious sore face from EV-grin-itis...

 

[Kevin Sharpe]

Now, since the Curtis 1238e-7621 HPEVS Dual AC-34 Brushless Motor Kit - 96 Volt dual motor I originally linked to is, itself, $7900, that $15K is going to get near the limit fairly quickly with too many mistakes if that's the power level I'm going for. I also mentioned EV West's 818 kit as a very rough punch list but with something stronger than an AC-50 as the motor.

OEM components are a fraction of the cost of these 'old school' solutions... for example a complete Leaf drivetrain can be had for ~750 USD and that's already delivering 300HP

Personally I would look at using the BMW, Leaf, or Tesla drivetrains with a third party inverter. If you're unwilling/unable to modify the suspension then keeping the existing transmission with these motors is also an option although personally think it's pointless dragging around a shifting transmission

With regards to battery's both Leaf and Volt packs are available at low cost (750-3500 USD) and should provide the building blocks to meet your range and performance requirements. Have a look at Damien's latest project to see the Volt packs being used in anger

 

[mshobe]

With regards to battery's both Leaf and Volt packs are available at low cost (750-3500 USD) and should provide the building blocks to meet your range and performance requirements. Have a look at Damien's latest project to see the Volt packs being used in anger

Which project/thread is Damien's? Sorry I'm not quite clear on who the key players are here yet. :^)

I'm definitely interested in saving money where I can, but the real goal of this conversion is preserve the spirit of the Miata while improving its actual performance (not really its range). If I can get there with Leaf hardware and updated software, I'm cool with that.

 

[brian_]

Which project/thread is Damien's? Sorry I'm not quite clear on who the key players are here yet. :^)

Damien's main project is this one: Tesla Powered BMW E31 8 Series by "jackbauer"
Don't believe usernames Except mine.

I suppose by Damien's "latest project" Kevin means this one:
1,000 Euro EV Build

 

[brian_]

Personally I would look at using the BMW, Leaf, or Tesla drivetrains with a third party inverter. If you're unwilling/unable to modify the suspension then keeping the existing transmission with these motors is also an option although personally think it's pointless dragging around a shifting transmission

I agree that an electric motor in the engine location and keeping the stock transmission is bulky, heavy, and leaves little room for battery. On the other hand, I have seen no indication that anyone will be able to fit an OEM complete drive unit (motor with transaxle) into the rear of a Miata NA chassis. For balance (mass distribution), a Leaf unit would be great in a Miata if you could do it.

Damien quickly gave up on putting his Tesla drive unit into the back of the much larger (than a Miata) BMW 8-Series, and switched to a completely different and much less advanced suspension from another BMW model (and modified that suspension's subframe to fit the car) which did not get in the way of the drive unit. This sort of challenge sounds a little extreme for a first-time builder.

Nuts&Volts is working on putting a Leaf unit into the rear of a Nissan 300ZX, which is substantially larger than a Miata and has a different rear suspension which allows more room for the motor... and we don't know yet if it will go in.
300ZX Electric Conversion

Similarly, chrishazell is planning to put a Tesla drive unit in the rear of a Skyline (which has the same suspension as the 300ZX):
Tesla Powered Nissan r32 skyline

 

[Duncan]

Speaking as somebody who back in the mists of time stuffed a Lancia Beta twin cam unit into the front of my mini (real one not one of those huge BMW things) then I would say that you would have no real problem is putting a Leaf unit into the back of your Miata

You may have to source an early Leaf where the inverter is not mounted on top of the motor - or make up some plates to mount it elsewhere

 

[Kevin Sharpe]

I'm a electronics guy not a car guy and rely on other peoples expertise... that said, I meet little resistance from car guys when we suggest dumping the ICE transmission and changing the suspension systems... here's just one of the examples I love... a 'small' Tesla drive unit in an early Fiat 500

IF you have no option but to keep the old transmission then I'd look at the BMW i3 drivetrain which I understand can be easily separated into its component parts. Obviously people are also doing the same with the Leaf drivetrain but I understand that's more complex.

What I think is important for the OP to understand is that OEM components are much cheaper than the bespoke components that we've used historically.

 

[brian_]

Speaking as somebody who back in the mists of time stuffed a Lancia Beta twin cam unit into the front of my mini (real one not one of those huge BMW things) then I would say that you would have no real problem is putting a Leaf unit into the back of your Miata.

My guess is that this assumes that there is "no real problem" with replacing the front half of the rear subframe and substantially modifying the suspension.

To put this in perspective, the Lancia twin cam from the Beta is a small inline 4-cylinder transversely mounted engine. The Mini came with a very small inline 4-cylinder transversely mounted engine. The Lancia unit is definitely bigger and not designed to fit the oddball Mini transaxle (which sits under the engine), so this would not be an easy swap, but the two engines are more alike than they are different. They're certainly more alike than a Miata diff and Leaf drive unit.

I think it will be great if a Leaf drive unit can drop into the back of an NA Miata with nothing but some ball peen hammer work on the floor and fabbing up a couple of brackets. I just don't think it's safe to assume that will happen, and in all of the projects described and discussed in this forum - including several NA or NB Miatas - I haven't seen anyone fit a motor in the back, let alone transversely. If anyone finds an example, please share it.

Try a web search: has anyone ever put a EV drive unit in the back of a Miata? It's great to be the first, and if something is ever done someone has to be the first to do it... but that doesn't mean you should jump off a building while flapping your arms and count on being the first to fly that way before hitting the ground.

 

[brian_]

I'm a electronics guy not a car guy and rely on other peoples expertise... that said, I meet little resistance from car guys when we suggest dumping the ICE transmission and changing the suspension systems...

I'm a car guy and IT professional, but acknowledge and respect the experience of others in both fields. As a car guy I realize that when an object is bigger than the space where you want it, you must move and modify stuff; it's not like computer coding, where there are no physical space limitations. The code to describe an elephant can be stored in the same location as that for a mouse, but a real elephant just doesn't fit in mouse hole.

One thing I appreciate in both fields is the range of work already done by others and available to build on; it's essential in electronics, in coding, and in automotive systems. For instance, Kevin's Telsa-powered VW is using a complete suspension from an aftermarket supplier that bolts into the stock bus body and doesn't interfere with the Tesla drive unit. Is there a Miata motor-mounting rear subframe waiting out there in someone's catalog?

... here's just one of the examples I love... a 'small' Tesla drive unit in an early Fiat 500 .

I don't see any Fiat 500 suspension or structure there. Didn't it fit?

What I think is important for the OP to understand is that OEM components are much cheaper than the bespoke components that we've used historically.

I agree that they are a better deal, as long as you can work with them. OEM motors are more compact, for the same power output; they use current technology, while most aftermarket motors are adaptations of traditional industrial designs... often obsolete even in industrial use.

What we should all understand is that a motor and transaxle with differential (the typical modern EV drive unit) is much bigger than just a traditional final drive (differential); it's also a different shape. That's not very high-tech or trendy, it's just the real world. Maybe in this case that won't be a problem, the ideally desired motor and transaxle will fit where it is wanted, and we'll all be very happy.

 

[brian_]

Here is the underside of an NA Miata body (just the rear part, cut off at the rear of the doors, standing nose-down):

You can see the circular spring pockets just behind (above in the photo) the axle line, but the entire suspension and subframe have been removed (it was posted by someone using the body section to build a trailer).

The odd offset hole is where the top of the fuel tank is exposed through the floor - that's prime real estate for a something like a Leaf drive unit (which sits on and ahead of the axle line), since of course a fuel tank won't be needed, and if the motor is in the rear the entire battery will likely be in the front.

The Leaf motor is on the right-hand side of the car, and in the photo there is a quarter-circular depression in the Miata's floor on that side... but that's for the spare tire which rides in the trunk, high over the suspension. Lose or relocate the spare, and that bit of floor can be modified if required, but it's already high and it's far enough back that it might only be a concern for a Tesla drive unit (which sits on and behind the axle line).

I stumbled across a diagram of body measurements and a diagram of reference locations in a discussion in a different forum (the second one apparently from the Mazda shop manual), and intended for body shops to ensure correct body panel alignment in repairs. This sort of documentation is available for all normal production cars. They show the substantial space between the frame rails, in which all sorts of good and interesting stuff can be done.

The challenge is that none of this shows the Miata's suspension or subframe. For some projects (such as Duncan's Fiat 500 example) that doesn't matter because the builder buys or fabricates a complete suspension and subframe to suit the drive hardware being installed in the big space; for most projects that matters a lot because the car needs a suspension and one comes with it which was designed for different drive hardware.

 

[Satisaii]

Since I have never posted here before, I will start with a bit of an introduction.

I am the engineer and technician for 949Racing / Supermiata. We have built some of the fastest and most reliable Miata race cars in North America. We are in the engineering study phase of converting one of our street cars.

The path to EV that you started this thread with is definitely the easy way to get going. Performance will be okay but you will be out enjoying your car in a reasonable amount of time. One thing to look out for here is that your 5 speed transmission is safe to about 175 ft-lbs of torque. Past that it will fail at some point. The 6 speed is slightly better; keep it below 275 and it will last indefinitely.

I am planning on going the mid / rear mount. The Leaf and Tesla small should fit without modifying the suspension mounting points. I would only need to cut the body out (a lot) and design a new rear subframe. From a few rough measurements I have done, the Tesla large will fit between the wheel wells. This will mean redoing the frame rails, subframe, and rear suspension. This should be fun, but will be a couple of years to do.

I will have a complete scan of a Miata tub sometime next week. At that point I will start doing some drawings and determine which route to take. Once I have something to post I will start a build thread on it.

 

[Kevin Sharpe]

For instance, Kevin's Telsa-powered VW is using a complete suspension from an aftermarket supplier that bolts into the stock bus body and doesn't interfere with the Tesla drive unit.

A suspension system that we modified

Possibly more relevant to this discussion is the bespoke system that's being developed for my friends VW Beetle conversion (here)... I don't have many details yet but last time I met the car guy it didn't seem to be a problem to upgrade the system to cope with ~350 HP

I don't see any Fiat 500 suspension or structure there. Didn't it fit?

As I said previously most car people don't seem phased by these challenges... here for example is a mid-engined 500 Abarth built on the 'new' Fiat 500 platform

 

[brian_]

I am planning on going the mid / rear mount. The Leaf and Tesla small should fit without modifying the suspension mounting points. I would only need to cut the body out (a lot) and design a new rear subframe. From a few rough measurements I have done, the Tesla large will fit between the wheel wells. This will mean redoing the frame rails, subframe, and rear suspension. This should be fun, but will be a couple of years to do.

It's good to see a well-informed and reasonable view of this situation.

I will have a complete scan of a Miata tub sometime next week. At that point I will start doing some drawings and determine which route to take. Once I have something to post I will start a build thread on it.

Excellent!
I'm looking forward to that.

 

[brian_]

As I said previously most car people don't seem phased by these challenges... here for example is a mid-engined 500 Abarth built on the 'new' Fiat 500 platform

That's great, but it is very far from what "most car people" build. It is in an entirely different world from what someone doing their first car project, and needing someone else to remove the engine first, should consider.

 

[brian_]

Possibly more relevant to this discussion is the bespoke system that's being developed for my friends VW Beetle conversion (here)...

That would be very relevant to the Miata, if only the Miata had semi-trailing arm rear suspension which leaves the entire space around the axle line and behind it completely empty for a Tesla drive unit. It doesn't.

Clearly, the easiest way to do an EV conversion on a Mazda Miata while taking advantage of the excellent value of salvaged production EV components is to sell the Miata and buy an old Beetle or air-cooled Porsche... then presumably move the "Miata" badge over.

 

[brian_]

For instance, Kevin's Telsa-powered VW is using a complete suspension from an aftermarket supplier that bolts into the stock bus body and doesn't interfere with the Tesla drive unit. Is there a Miata motor-mounting rear subframe waiting out there in someone's catalog?

A suspension system that we modified

Perhaps I misunderstood, but as I read the thread the modification to the Red9Design rear suspension was to add Tesla drive unit mounting provisions to the Red9Design subframe. Great work, but I don't recall any modification of the suspension components at all... which were designed to fit in the space available in a bus with a wide engine adjacent to the rear axle, and a transmission extending in front of the axle.

Kevin has provided great information about the whole bus build, including a photo of the Red9Design system as delivered, and with the rear subframe portion replaced by one incorporating mounts for the Tesla drive unit. The silver-coloured components (the entire suspension, plus the forward subframe portion) are the parts used as-is from Red9Design; the darker coloured component is a bolted-together prototype of a custom subframe section and motor mount... of greater complexity than any structural component built for most DIY EVs.

Again, where is that aftermarket suspension for a Miata which fits around either a Leaf drive unit or a Tesla drive unit (or a VW flat-four and transaxle)? And again, maybe the space between the Mazda parts will be wide enough for a Leaf or Tesla drive unit, but the existence of such a suspension for the Bus says nothing about the fit in a Miata.

 

[mshobe]

OP here. I am excited to have kicked off this discussion and really appreciate all the perspective, possible solutions, and exciting speculation.

As a total newbie, I guess I'm still a little bit mystified at how, in 2018, specifying an EV conversion isn't a lot closer to specifying a gaming PC. I don't mean to say that I'd expect to convert *any* car into a killer EV with a couple clicks on Amazon. (I'd sure like to, though.) But I am really surprised that no one has tried harder to standardize an approach to popular, semi-modern ICE platforms, like BMW 3s, Audi TT/A3/A4, Miatas, MR2s, S2000s, and even 993/996 911s. Or just chosen one with lots of available inventory and a plentiful aftermarket full of parts/accys, like the Miata, and gone deep to create an enthusiast-friendly kit that you can drop in with a couple days' labor from a partner shop/mechanic. I know http://www.zelectricmotors.com/ and a few other boutiques do something like this, but it's not nearly the DIY ethos I see and am inspired by here.

I'm still stuck at the basics –*which motor, whether to stick with existing transmission or try to find/fab a direct drive, how to do the math to get the amps/volts right, where to place the batteries, which batteries to get, how to easily support the existing vehicle's core 12V bus, how to update the throttle and instrumentation, how to wire everything together without killing myself or someone else who wants to help me with the project. Sorry y'all –*I probably should've started the thread there!

I also realize the FAQ I've outlined above is probably answered 10x over in the Forum somewhere. Maybe I should just read everything in http://www.diyelectriccar.com/forums/showthread.php/ev-information-669.html and see if it all comes together. This SEVA FAQ is pretty good, too.

My manifesto: Make It Easy-ish. I realize a DIY EV is a project that requires conviction and a bit of smarts, and is not something you can order like a hot NVIDIA GPU and an SSD drive on NewEgg. But golly, I really wish it was.