[TheFuzzReturns]

Hi! I have a 1990 RX7 hatchback which has had a rotary, then a chevy 350 v8, and now an empty engine bay! I've been reading up on EV conversions and I'm trying to plan out a conversion for the RX7, I was thinking of mating a nissan leaf motor to a manual transmission and maintaining my driveshaft for convenience.

I have access to a fair amount of tools, but bot specifically much in the way of fabrication (bar a drill press and 25 ton hydraulic press). My experience is mostly with vehicle maintenance, but I like to challenge myself with more difficult endeavors. I've had 7 years of entry engineering school through my former middle and high schools, so I'm not completely electrically illiterate.

I have access to a relatively large amount of tool batteries I recycle, I shuck the shells and get the cells inside. Testing them and tossing the burners/ones that self drain. I'm shooting for 60 miles on a full charge, I really just want to make a little sports car to fling around town and use for running errands.

I'd like to at least match the stock hp of my N/A rotary engine, so 160hp, but I saw Paul Holmes 200kw controller and would love to have 200kw (268hp) as peak power, even if only for short bursts.

Budget is flexible as it's a labor of love rather than necessity. Ideally I'd like to stay below 2-3k excluding batteries, but if I need to go over to hit the hp I'd like, I'm "happy" to shell out more.

So far I've been looking into using either a first or second gen Nissan leaf motor and an opensource controller. Is the controller here 200kW AC Motor Controller for Electric Car also an inverter? Furthermore it doesn't look like Paul is selling the boards required for that controller anymore. What other options are out there?

My general understanding is that I need a motor, an AC controller/inverter, a battery pack, an accelerator, and some kind of diagnostics panel at minimum. Anything I'm missing?

Thanks in advance for all your help! I'm excited to join the community and learn with you guys!

 

[brian_]

Is the controller here 200kW AC Motor Controller for Electric Car also an inverter?

Yes, the "IGBT half-bridges" in the component list are the power transistors which form the inverter power section. While Paul just calls it a "controller" (which is fine) it is both the inverter and the system which controls the inverter.

 

[MattsAwesomeStuff]

So far I've been looking into using either a first or second gen Nissan leaf motor and an opensource controller. What other options are out there

Might as well re-use the Leaf controller, not replace the inverter entirely.

Damien sells a board that mimics the CAN signals to the Leaf controller. EVBMW.com

Johannes sells a board that directly tells the Leaf controller what to do (even things it originally didn't do). OpenInverter.org

 

[TheFuzzReturns]

Might as well re-use the Leaf controller, not replace the inverter entirely.

Damien sells a board that mimics the CAN signals to the Leaf controller. EVBMW.com

Johannes sells a board that directly tells the Leaf controller what to do (even things it originally didn't do). OpenInverter.org

Are there any major differences between the gen 1 and gen 2 leaf inverters? I know gen one is standalone while the others are bolted to the motor. Will both be able to hit the 200kw mark I'm shooting for for bursts?

 

[266917]

Is it possible to get real power from the Leaf motor when used with a single output shaft? I thought I remembered someone saying you had to severely limit the torque, but they were discussing using it for a boat application and it may have had more to do with cavitation or something and not mechanical engineering.

 

[TheFuzzReturns]

Yes, the "IGBT half-bridges" in the component list are the power transistors which form the inverter power section. While Paul just calls it a "controller" (which is fine) it is both the inverter and the system which controls the inverter.

Is there any merit to building your own inverter over using the nissan leafs with a custom brainboard? Not sure if the leaf requires extra inputs or if that's all handled within the brain board like Johannes openinverter.

 

[TheFuzzReturns]

Is it possible to get real power from the Leaf motor when used with a single output shaft? I thought I remembered someone saying you had to severely limit the torque, but they were discussing using it for a boat application and it may have had more to do with cavitation or something and not mechanical engineering.

I haven't read anything about that as of yet. If you find a link, I'd love to read it!

 

[brian_]

Is there any merit to building your own inverter over using the nissan leafs with a custom brainboard?

At one point building your own was the only choice; now, it would only make sense to me if you want to use a power or current level beyond what the stock inverter's power section can handle.

 

[266917]

I haven't read anything about that as of yet. If you find a link, I'd love to read it!

Here's where I saw it: AC / Large Motor Kits :: Nissan Leaf Drive System (Used)

"If you wanted to use this for a boat you can open the transmission and pin some gears together allowing use of one side of the output shafts at ~1200 rpm. Mounting it is up to you."

Like I said, I MAY be reading too far into it, and maybe they only meant specifically when using it for a boat application for a different reason, but my brain said "Oh, if you run it single output, you have to pin it and then you're limited to 1200 rpm." It was enough to put me off buying one for a single output application, but I'd love to be wrong.

 

[brian_]

Here's where I saw it: AC / Large Motor Kits :: Nissan Leaf Drive System (Used)

"If you wanted to use this for a boat you can open the transmission and pin some gears together allowing use of one side of the output shafts at ~1200 rpm. Mounting it is up to you."

Like I said, I MAY be reading too far into it, and maybe they only meant specifically when using it for a boat application for a different reason, but my brain said "Oh, if you run it single output, you have to pin it and then you're limited to 1200 rpm." It was enough to put me off buying one for a single output application, but I'd love to be wrong.

This is referring to using the motor complete with the transaxle that is attached in the Leaf, not just the motor. By "pin some gears together" they mean lock the differential so that it can drive one output (which is supposed to drive one front wheel of the Leaf) without just spinning the unused output - this has nothing to do with strength. The shaft speed is limited to about 1200 RPM because that corresponds to a road speed of about 90 MPH or 145 km/h and a motor speed of about 10,000 RPM; the transaxle has an overall gear ratio of 8:1 and the motor can produce its full rated power (80 kW in early versions) up to 10,000 RPM with the Leaf's battery voltage.

There is nothing about torque limits in this; the speed limit would apply even if both transaxle outputs were used. The maximum torque would be the motor torque (about 280 Nm for the original version) multiplied by that same gear ratio (so about 2200 Nm), and it would sustain that to about 2800 RPM at the motor, or 350 RPM at the output shafts... then it is power limited past that.

 

[brian_]

I've been reading up on EV conversions and I'm trying to plan out a conversion for the RX7, I was thinking of mating a nissan leaf motor to a manual transmission and maintaining my driveshaft for convenience.

My understanding of this is that the plan is to remove the Leaf motor from the transaxle, and connect just the motor to the Mazda transmission - the classic EV conversion method. In this case, the various issues raised by Richter12x2 of using the EV's transaxle as a reduction gearbox don't apply.

You don't actually need a regular transmission with a motor like this. As long as you have enough battery voltage the motor will produce the rated power up to 10,000 RPM, so you can do what Nissan does and use a fixed reduction ratio of gearing. The reduction ratio of the RX-7's final drive (the ring and pinion at the differential) is probably 4.10:1 (or maybe 4.30:1 if you have limited slip) and that isn't enough (torque to the wheels at low speed would not be high enough), so you would need an additional 2:1 or so of gearing between the motor and the final drive, using a small extra gearbox instead of the whole original transmission.

 

[266917]

I'm glad to be mistaken... everything I'd seen so far in other conversions was using the entire Leaf unit, I wasn't aware you could just pull out the motor itself. I'm very interested in how this turns out.

 

[brian_]

... everything I'd seen so far in other conversions was using the entire Leaf unit, I wasn't aware you could just pull out the motor itself.

Some motors are not readily separated from the transaxle - the classic Tesla drive units are the most common example, and use the same aluminum casting as one side housing of the transaxle and one end housing of the motor. The Leaf (like most other EVs) has a motor which can be unbolted from the transaxle and does not share lubrication with the transaxle, so it works fine without the transaxle. The challenge when trying to replace an engine with a motor this way is that the end of the motor shaft is not like the end of the engine's crankshaft, so some sort of adapter is required... and it is not available except by custom design and fabrication.

Like most EV motors, the Leaf motor has a shaft with a male splined end.

Certainly if it fits at the axle line, using the complete drive unit (motor with transaxle) is a good way to go, rather than adapting the motor to a transmission intended for a different purpose. That might work with an RX-7, but in the case of this generation (the FC) it would require structural changes to the car, substantial modification of the rear subframe, and would almost certainly have difficulty with the rear suspension (especially the lateral control rods). The FC is a design which is not well suited to using the complete drive unit mounted in the rear.

 

[TheFuzzReturns]

My understanding of this is that the plan is to remove the Leaf motor from the transaxle, and connect just the motor to the Mazda transmission - the classic EV conversion method. In this case, the various issues raised by Richter12x2 of using the EV's transaxle as a reduction gearbox don't apply.

You don't actually need a regular transmission with a motor like this. As long as you have enough battery voltage the motor will produce the rated power up to 10,000 RPM, so you can do what Nissan does and use a fixed reduction ratio of gearing. The reduction ratio of the RX-7's final drive (the ring and pinion at the differential) is probably 4.10:1 (or maybe 4.30:1 if you have limited slip) and that isn't enough (torque to the wheels at low speed would not be high enough), so you would need an additional 2:1 or so of gearing between the motor and the final drive, using a small extra gearbox instead of the whole original transmission.

Eventually I'd like to fashion my own gear box, but for the time being I'd be mating it to either a t5 or t56 manual transmission (what I have from previous engines). I have a 4.10 limited slip diff!

 

[TheFuzzReturns]

Some motors are not readily separated from the transaxle - the classic Tesla drive units are the most common example, and use the same aluminum casting as one side housing of the transaxle and one end housing of the motor. The Leaf (like most other EVs) has a motor which can be unbolted from the transaxle and does not share lubrication with the transaxle, so it works fine without the transaxle. The challenge when trying to replace an engine with a motor this way is that the end of the motor shaft is not like the end of the engine's crankshaft, so some sort of adapter is required... and it is not available except by custom design and fabrication.

Like most EV motors, the Leaf motor has a shaft with a male splined end.

Certainly if it fits at the axle line, using the complete drive unit (motor with transaxle) is a good way to go, rather than adapting the motor to a transmission intended for a different purpose. That might work with an RX-7, but in the case of this generation (the FC) it would require structural changes to the car, substantial modification of the rear subframe, and would almost certainly have difficulty with the rear suspension (especially the lateral control rods). The FC is a design which is not well suited to using the complete drive unit mounted in the rear.

Hit the nail on the head! I'd love to set up the powertrain in the rear and use the huge engine bay for batteries, but even with the gas tank out there's just not enough room for the complete motor and gearbox setup without cutting.