1993 Rx7 + Tesla Motor

[mike.bmw]

Oh man, this is going to be fun. And you are correct, I too have always wanted an FD RX-7.

[rjmcdermott81]

This is awesome! What are you going to do for batteries? I don’t see a problem with setting the axles backward, as long you don’t exceed their limits, usually 25-30 degrees. The wear will be accelerated, and slight drop in torque transferred, but minimal.

Excellent - thanks for the feedback on the axles. I will press forward.

For batteries I am evaluating two options. To drive the tesla motor and get the killer power output you really need a 400V system.

1. Chevy Volt battery pack - these are already setup in a 360V configuration and they are cheap and easier to cool. But they are only have 16kW of capacity. You can fit two in the Rx7 which gives you 32kW hours (hopefully 80+ miles of range)
2. Tesla Model S - these have the best power density but each module is only 22V so you have to put an entire car's worth in to get to 400V. That way you get to 60-80kW of capacity which gives you awesome range but space is the big constraint.

I'm going to shoot for tesla batteries but I won't be able to measure it all out until I get the drive unit installed and the motor pulled.

[rzerob]

Subscribed.

[varg]

Going to be interesting to watch this. It would be a real shame to add a bunch of weight to that, one of the best Japanese car chassis. Weight of a Chevy Volt pack seems to be around 435lbs from what I'm reading so you could likely do the conversion using that pack without a terrible amount weight gain. Seems an 85kWh Model S battery pack weighs 1200lbs, and since I couldn't find a weight for a 60kWh pack, I'm assuming it weighs approximately proportionally less; still ~850lbs. If you just split it up and rewired it so that it would fit in the existing chassis the battery would add at least 300lbs to the weight of the car vs its stock powertrain assuming the weight gained for the subframe mods, motor and gearbox in the rear vs the stock differential comes out neutral with the gas tank removed.

CV axles will wear out faster if you increase their angles, but with the kind of instantaneous torque application you're talking about I'm guessing you'll break parts if you put sticky tires on it anyway and will have to get aftermarket stuff and strengthen the chassis.

[rjmcdermott81]

Varg - thanks for reminding me! I wanted to record the weight change accurately so I took it in stock form and had it weighed. This way we'll be able to see how having that motor out back changes the F-R weight ratio. I was surprised at how heavy it was at 3,079 lbs.

[varg]

That's heavier than I was expecting by at least a hundred pounds, but it looks like the car is an optioned out automatic with a sunroof so I suppose it makes sense that it weighs more than the numbers often quoted in specs. No wonder it felt kinda slow...

Glad to see you're going to weigh before and after, people don't usually do that with swaps.

[oekundar]

subscribed for another cool build!

[2mAn]

:popcorn:

[rjmcdermott81]

I took the gas tank out yesterday and now I'm getting a better view of the space I have to work with

[rjmcdermott81]

No mas wheel well.

[Metallated]

Cool progress!

I'm interested to see how the wiring and management goes, I've heard those parts are difficult, especially using the Tesla computer/software (?)

[rjmcdermott81]

Cool progress!

I'm interested to see how the wiring and management goes, I've heard those parts are difficult, especially using the Tesla computer/software (?)

Yes I am too. There is a ton of what seems to be FUD on the internet about this. Basically you have a bunch of people charging a $hitton and then others with reasonable priced options. I'm going with the opensource controller from EVBMW and I already have the logic board. This is the same solution that I believe jon volk used in his e30. I saw the people selling the expensive solution post on his instagram about how he was going to toast the motor and/or never get it running. He pressed forward and seemed to have success.

The wiring I'm sure can get complicated but the inputs into the controller are crazy simple 5-6 wires or something. And you just use an e46 throttle pedal.

Before I pulled the trigger I put together a quick rundown of the options that were available as of about 6 months ago:

1. Open Source (Ebay + EVBMW)
   • Control Method: EVBMW PCB
   • Total Price (Base Drive): $4,140*
   • Total Price (Base Drive + Quaife): $6,140*
   • Total Price (Performance Drive): $5,140*
   • Total Price (Performance Drive + Quaife): $7,140*
   • Includes:
     • Damien Logic board: $739.20 shipped
     • Used Tesla drive unit (Base): $3,000 shipped
     • Used Tesla drive unit (Performance): $4,000 shipped e46 Pedal: $100
     • Low voltage wiring/miscellaneous: $200
     • Optional Quaife Differential: $2,000
   • Comments: This options requires you to do quite a bit of research on your own and support is provided by the Openinverter forum. It isn't plug and play out of the box. Prices estimated based on Ebay auctions September 2019.
     
     If you get into a jam Damien offers paid support in a few forms - single email (€10), 30 minute support call (€60), or a full day (
     €450).
2. HSR Motors (057 Technologies)
   • Control Method: Outside controller talking to Tesla board
   • Total Price (Base Drive): $7,999
   • Total Price (Base Drive + Quaife):
   • Total Price (Performance Drive): $10,999
   • Total Price (Performance Drive + Quaife):
   • Includes:
     • (1) Large Tesla Drive Unit - BASE (refurbished)
     • (1) 057 Technology Drive Unit Controller
     • (1) Accelerator Pedal (Dual hall-effect)
     • (1) Basic low-voltage wiring (controller, motor, pedal, etc)
     • (1) High-voltage wires with connections for drive unit
     • (1) Instructions, pinouts, protocols for controller, etc
   • Comments:
3. EV Controls
   • Control Method: Outside controller talking to Tesla board
   • Total Price (Base Drive): $6,799*
   • Total Price (Base Drive + Quaife): $8,799*
   • Total Price (Performance Drive): $7,799*
   • Total Price (Performance Drive + Quaife): $9,799*
   • Includes:
     The EV Controls T-1C Controller that communicates with the inverter over the CAN bus, and will allow you to do the following;
     • -Engage drive, neutral and reverse modes via the 7″ touchscreen,
     • -Adjust peak power output and regenerative braking power levels via the touchscreen,
     • -Display the following data on the 7″ touchscreen;
     • -Drive mode (D, N ,R)
     • -Traction pack voltage (HV)
     • -Inverter 12V supply voltage
     • -Accelerator position
     • -Stator current
     • -Actual power in kilowatts, positive or negative (regenerative braking)
     • -Max power limit
     • -Max regen power limit
     • -Five internal inverter temperature readings
     • -Vehicle speed (user adjustable scaling to account for wheel diameter)
     • -Current brake pedal and regen state
     • -Diagnostic data.
     
     
     $3499 for everything listed above.
   • Comments: Requires pedal and low voltage wiring added to the price.
     
     I don't see customizability to other gauges so I believe you need to be satisfied with the 7"" screen output.
     
     Limited to S-85 and P-85 drive units
4. Stealth EV
   • Control Method: EVBMW PCB
   • Total Price (Base Drive): $7,800
   • Total Price (Base Drive + Quaife):
   • Total Price (Performance Drive):
   • Total Price (Performance Drive + Quaife):
   • Includes: Tesla Base Rear Drive Unit: Drive units removed from Tesla Model S and Model X vehicles with less than 25,000 Miles. Each drive unit houses an AC induction propulsion 3-Phase/4-Pole motor that can spin up to 16,000 RPM in large drive units and 18,000 RPM in low power and front drive units. The housing also includes the controller w/ Inverter and differential. Each drive unit comes with our own Stealth EV Controller Board replacement that allows for CANbus communication with any BMS, VCU, Hall Throttle, and switchgear. Wi-Fi access also comes standard for “in the field” or “on the fly” controller adjustments, no longer requiring USB connectivity or proprietary equipment.
   • Comments: Appears to be a drive unit with the EVBMW (Damien's) board installed. Requires pedal and low voltage wiring added to the price.
5. Zero EV
   • Control Method: Replacement PCB - based on EVBMW but further customized by Zero EV
   • Total Price (Base Drive): $12,159
   • Total Price (Base Drive + Quaife): $13,509
   • Total Price (Performance Drive): $17,086
   • Total Price (Performance Drive + Quaife): $18,436
   • Includes: Large Standard Drive Unit, Zero EV Control System, Open Diff, Drive Shaft Stumps, Display, Throttle, Gear Selector & Low Voltage Junction Box with Loom.
     
     Options:
     • Performace Large Drive Unit 150BHP increase ?3,995
     • Quaife ABT Limited Slip Diff (Highley recommended) ?1095*when bought with drive unit kit.
     • Quaife Spool Locked Diff (for drif/ off road use only) ?750*when bought with drive unit kit.
     • Drive Unit Coolant System Upgrade ?795
   • Comments:
6. EV West Drop in Unit
   • Control Method: Outside controller talking to Tesla board
   • Total Price (Base Drive): $11,900
   • Total Price (Base Drive + Quaife):
   • Total Price (Performance Drive):
   • Total Price (Performance Drive + Quaife):
   • Includes: Includes: Tesla motor, inverter, gear box, dash display and control unit (EV Controls), throttle pedal, throttle pedal plug and pins, brake switch, brake switch plug and pins, encoder plug and pins, inverter plug and pins, axle clips, 2 axles, pre-charge relay, and pre-charge resistor.
   • Comments: Looks to be the EV Controls controller with a drive unit and all the trimmings to make it go out of the gate.
     
     I don't see customizability to other gauges so I believe you need to be satisfied with the 7"" screen output.
     
     Limited to S-85 and P-85 drive units
7. EV Shop EU
   • Control Method: EVBMW PCB
   • Total Price (Base Drive): $12,165
   • Total Price (Base Drive + Quaife):
   • Total Price (Performance Drive):
   • Total Price (Performance Drive + Quaife):
   • Includes: This kit includes the Tesla motor, inverter, gear box, power cables and drive shafts. And, Damian’s EVBMW inverter board.
   • Comments: Looks like they are basically packaging a used drive unit with Damian's inverter board installed.
8. EVTV.me
   • Control Method: Outside controller talking to Tesla board
   • Total Price (Base Drive):
   • Total Price (Base Drive + Quaife): $16,995
   • Total Price (Performance Drive):
   • Total Price (Performance Drive + Quaife):
   • Includes:
     • Tested and refurbished Drive Unit Motor/Inverter/Gearbox Assembly from salvaged Tesla Model S with Quaife ATB Differential installed.
     • GEVCU Controller with Tesla control software
     • Wiring harness
     • EVIC Tesla Display from Andromeda Interface
     • PKP2400 CAN Control Switch Panel for Tesla Drive Unit
     • IVTSCALE 1000Amp current/voltage sensor
     • Custom Speedhut CAN Gage set for Tesla Drive Unit
   • Comments:

*These prices estimated using ebay prices for some of the hardware to make it a more complete solution for comparison.

[zwill23]

Going all in with the spare wheel well mincing! Awesome to see you jumping into it, I think quarantine may have been a blessing in disguise for you ;)

Those axle angles really don't look too bad, do you know the power limit on the stock axles? A quick search shows people running 500hp+ with stock RX7 axles. I'll bet the insta-toque from the electric motors would put a good deal of stress on them, but at your power limits you might just get away with it. Especially considering the LS RX7 guys seem to still run stock axles.

[rjmcdermott81]

Thanks zwill23. I'm trying to keep the ball moving forward in this craziness. I honestly don't know what I'll do on the axle front. I have the tesla axles which have the proper splines for the insert into the gearbox. I think I use the outboard RX7 joint and inboard tesla joint and order an axle to go inbetween... Or maybe just completely custom. Not sure yet.

I did some final cutting on the rear subframe. At this point, I think my next step is to mock it up with the actual drive unit so I can add a cross support that will keep everything stable while I unbolt it from the jig. I originally planned to take this somewhere for final welding but...with the lockdown I'm gonna take a go at it. Worst case a weld cracks in the future but at least I'll have the design.

[gnmzl]

This is way too cool. Good work, will be keeping an eye on this one.