# Mazda RX7 Conversion



## brian_ (Feb 7, 2017)

I'm impressed: almost no one else has modified or fabricated a subframe to make a Tesla drive unit - particularly the large unit - fit in a stock production street suspension other than a simple semi-trailing arm type.


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## brian_ (Feb 7, 2017)

For those not familiar with this model...
All RX-7 variants are rear wheel drive, with a Mazda rotary engine in front. The "FD" generation of the RX-7 has a 5-link independent rear suspension, with a subframe supporting the final drive unit (differential housing) and tying the inboard suspension mounts to the body structure.

This builder has removed the middle of the subframe and replaced that part with tubing designed to fit the Tesla drive unit instead of the original final drive. The spaces originally occupied by the engine, transmission, propeller shaft (driveshaft) and possibly some of the fuel tank space are now available to contain the battery and various ancillary components. The fuel tank is behind and above the axle; it's not clear to me how much of that space is occupied by the Tesla motor and inverter.

A question, though, for rx7r3ev: the front mount for the Tesla drive unit is clearly shown (and looks good ) but how is the rear mount handled? It's much further back than the RX-7 subframe extends, and it must take a substantial part of the drive unit weight.


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## rx7r3ev (Dec 11, 2018)

Thanks. For the drive unit rear mount, I'm using a cross member to secure the mount point for it. I have remove the fuel tank to make space for this and have also fabricated a box close to the rear of the car for space storage that can be utilized for battery or other auxiliary. 

I'll be using two Chevy volt battery. Placement is on the transmission tunnel, engine bay, and rear trunk. Still fabricating the holder/mounting for the battery. Most work is done on the weekend so progress is slow.

Progress for today - I have Damien's Gen 2 controller board configured and installed. Be testing this soon.

I have couple of questions for safety and wonder what DIY conversion folks have used. 

First, in case of a crash what is the technique or way to disable the HV pack? I've been contemplating of using an inertia relay on the negative contactor.

Second, in case of a flood (or if the car falls off a river/water), again to disable the HV pack what does folks commonly used for this?

There's probably more scenarios that needs to be address with safety that I've haven't though of but those two above sticks out for me.


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## evric (Oct 26, 2008)

Hi rx7r3ev,

I'm in Australia and for my ev conversion, I used a Ford inertia sensor switch (which in the Ford (Falcon) turns off the fuel in case of an accident). I have attached a photo of the one I am using. There is a button (switch) on the top to reset it.
I used it to disable the main contactor. It must be mounted vertical.
Part Number is Pollak PBT-GF15

These days there are also airbag crash sensors that you could use as well, as long as it has an accessible reset switch.
I have had no experience with the airbag ones.

Please let me know what you end up using.
All the best with your project.

Eric
South Australia
...........................


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## rx7r3ev (Dec 11, 2018)

Thanks Eric. I'll definitely take that into consideration. Still awaiting info on how to address when the car is in flood water and how to automatically disable the contactors.

For progress:
The fabrication of the engine bay battery tray/carriers has started. Also installed the cv axle shaft.


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## Tomdb (Jan 28, 2013)

One quick and kind of rude remark, did you not list out use cases and see when you really need a solution?

Flood water, when will your car encounter them. 
A- when you are driving, turn the car off yourself (or who ever is driving)
B- when parked, the car is not on so the contractors are closed
C- when charging, just get a water warning sensor.

example: https://www.aartech.ca/vip1000-h2o-flair-waterguard-water-detector-5-24vdc-white.html

Build is looking quite good, a rx7 is tight looking forward to seeing you cram two hole Volt packs in.


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## rx7r3ev (Dec 11, 2018)

Tomdb said:


> One quick and kind of rude remark, did you not list out use cases and see when you really need a solution?
> 
> Flood water, when will your car encounter them.
> A- when you are driving, turn the car off yourself (or who ever is driving)
> ...



In the previous post above the use case I've stated is "when the car falls off a river..." -- Also a 'rude remark' for you. 

Pretty much safety for unexpected events like somebody T-boned you and your car falls off a pond of water and cant really do your A-B-C you listed and all you can just mutter is "oh crap!"

Thanks for the info on the H20 detector that's new to me and should be a consideration.


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## rx7r3ev (Dec 11, 2018)

Updates on the project: 

Open up the transmission/Drive shaft tunnel to fit a couple sections of Chevy volt battery. For simplicity, I call/classify the Chevy volt battery as composed of Large, Medium and Small sections. The transmission/Drive shaft tunnel will house the Large and Small section of the batteries. The engine bay will house two Medium and one small section. The trunk will house another Large Section. All in all there are two Chevy Volt battery packs.


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## rx7r3ev (Dec 11, 2018)

Installed the large Chevy Volt battery section in the custom box at the trunk. Fabricated an aluminum box as carrier for the battery to be secured using the original volt mounting hardware.


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## rx7r3ev (Dec 11, 2018)

Update: Progress been slow lately but got the batteries installed inside the tranny/shaft tunnel and also did some cable layout runs from the inverter going to the engine bay.


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## Dxta (Oct 2, 2017)

I like your conversion. Any updates on the project yet?


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## EVmattyP (May 12, 2019)




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## rx7r3ev (Dec 11, 2018)

Progress: Work has now transitioned to the engine Bay Area. Trying to get the best fitting and layout now for the contactor box and Tesla gen 2 charger in the engine bay. Also given the car some TLC wash.


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## rjmcdermott81 (Aug 14, 2019)

Hey - I'm trying to follow your path of greatness and do the same. Hoping you can give me some pointers.


I have a spare subframe in a jig and I'm about ready to start hacking into it. 











I'm looking at the rear of your subframe and it looks like you had to cut the rear tabs off that bolt to the car frame and make new ones (red). Did you have to cut the frame of the car here as well and weld in new panels?










Frame pic I'm talking about:


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## rx7r3ev (Dec 11, 2018)

The entire backend of my rear subframe have to go since I'm trying to fit the motor and have a similar to stock drive shaft axle alignment. The new tabs bolts where the old tabs use to be. If you want to keep the stock tabs, then your motor's diff will sit a little bit behind where the stock rear diff location was.


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## Mick_D (Aug 2, 2019)

Where did you get that mockup of the Tesla Drive Unit? I really need one of those!


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## rx7r3ev (Dec 11, 2018)

Mick_D said:


> Where did you get that mockup of the Tesla Drive Unit? I really need one of those!


I've pulled it 'out' your A$$.


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## Mick_D (Aug 2, 2019)

Wow. Just wow.



rx7r3ev said:


> I've pulled it 'out' your A$$.


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## rx7r3ev (Dec 11, 2018)

Mick_D said:


> Wow. Just wow.


Seriously, if you have stuff contribute please do so. Otherwise troll somewhere else Mark_D. 

Peace!


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## Mick_D (Aug 2, 2019)

All I did was ask where you got that cardboard mockup of the tesla drive unit. That's trolling? Your hostile response isn't bad form? Excuse the fuck outta me.






rx7r3ev said:


> Seriously, if you have stuff contribute please do so. Otherwise troll somewhere else Mark_D.
> 
> Peace!


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## Duncan (Dec 8, 2008)

I would have to agree with Mick D

I would also like to know where you got that cardboard model - if you made it yourself could you share the "plan" ?

I could see that being incredibly handy to a lot of people


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## MattsAwesomeStuff (Aug 10, 2017)

I'm guessing there's a language barrier here.

Unless you two know each other from somewhere else, there's no reason anyone should be upset. And I don't mean "You should handle criticism better" kind of "no reason", I meant, literally no reason, I'm perplexed how anyone got upset.

Full reset. Everything's fine.


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## Mick_D (Aug 2, 2019)

He refuses to answer my question and then calls me a troll, and you see nothing wrong with that? You need glasses.


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## rjmcdermott81 (Aug 14, 2019)

Thanks for the advice. I can't wait to get this rotary out of it.





rx7r3ev said:


> The entire backend of my rear subframe have to go since I'm trying to fit the motor and have a similar to stock drive shaft axle alignment. The new tabs bolts where the old tabs use to be. If you want to keep the stock tabs, then your motor's diff will sit a little bit behind where the stock rear diff location was.


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