# Mazda RX7 direct drive EV project: Input welcome!



## rickeolis (Aug 13, 2009)

Hi everyone,
I recently purchased a 1979 Mazda RX7 in order to build into a car I can race at the local track (road course racing), as well as possibly be a daily driver.
I have other cars, (Geo Metro, Mercury Tracer, etc.) so the daily driver plan isn't as much a desire as a good race car, but that thought is there too.
The RX7 has the entire interior removed already, and there is no engine or tranny in the car. The original driveshaft is in place connected of the stock rear-end. The body is in decent shape, and the brakes and steering components appear to be good too.
I want it to be very strong, but not one of those 2000+ amp things. If I could build it as a 1000 amp DC setup, that should give me what I need, considering how light the car is.
I'm looking at buying a 9" Advanced DC or Warp netgain motor. Then to get a solid controller and go from there. All I know of for controllers is the Curtiss line or Zillas (but I know I can't get one of those right now), so I might get some input there.
For weight and power reasons, I like the AGM Odyssey batteries, but am open to suggestion here too.
Am I right to consider a direct drive? Or should I buy a used tranny and go that route? That would be more weight, and have the need of a clutch and plate adapter too.
I currently race an '87 Corvette, but am going to sell it and go this route.
Thanks everyone-

-Rick-


----------



## Jimdear2 (Oct 12, 2008)

rickeolis,

If this were my project 

I would be pounding on EVnetics door for their new controller. I think that thing is going to be a racers dream. (I'll be talking to them about my next electric puller)

I would be looking at a race prepped converterless circle track powerglide. Low gear for those tight spots and direct for those long straights. Darn near indestructible too. Might be lighter then a stock Mazda manual as well.

With the right setup:
*Motor;* You'll need at least 5-6000 + usable RPM, that means big voltage or possibly AC.

*Controller; *1000 amps and big voltage. 

*Batteries; *Lots and Lots of watt hours with a 20C + discharge rate.

*Gearing* As needed for your performance requirements

Man, you should have a rocket ship from dead stop right up to 100 mph plus. 

A note on batteries, I'm using the Oddsey batteries in my pulling tractor. Lordy. . . can you pull amps from them, BUT they really just don't have the capacity for any kind of distance racing. From reading and research I think that A123 is the only option for road racing. The Headway cells also might work but I would do more research before I tied up that kind of money.

As I say . . . if this were My Project (I'd also need to be about 20 years younger)

This is going to be a FUN project

I'm no expert and I'm sure others will have there say but these are my suggestions.


----------



## rickeolis (Aug 13, 2009)

Thanks Jim,
 I appreciate the input!
 What does this mean: "a race prepped converterless circle track powerglide" Thanks...
 I went to the website for EVnetics, and they don't have ANY info posted so I don't know what to expect from them. I'll do some digging on the usual chat boards about them I guess.
 The Odyssey batteries need only to last about 15 minutes per racing heat, and I will be looking at putting a fresh set in for the next heat. It will cost some this way, but still be much cheaper than the A123's. I've already looked at pricing on them!!! Whew.

 I'm also wondering if an Advanced 9" motor will be enough for me. Does anyone push these pretty hard in a light car with lots of voltage for good results?
 Thanks again everyone-


----------



## Jimdear2 (Oct 12, 2008)

rickeolis said:


> Thanks Jim,
> I appreciate the input!
> 
> What does this mean: "a race prepped converterless circle track powerglide" Thanks....


Follow this link http://www.tciauto.com/Products/Powerglide/ It will get you some basic information on the circle track powerglide. This transmission is a two speed very light automatic transmission that has been modified to work without a torque converter and uses manual shifting. It also has the internal gearing that looks to work well with electric motor power bands. It is a very strong transmission. Another version is used in drag racing and can handle 1000 horsepower.

Since it is used extensivly in racing there are many suppliers of custom components, Actually it is possible to build a new transmission with all new aftermarket pieces.

It is also small enough that it should easily fit in the RX7 if I remember the available room form when I still worked on them.



rickeolis said:


> I went to the website for EVnetics, and they don't have ANY info posted so I don't know what to expect from them. I'll do some digging on the usual chat boards about them I guess.
> 
> The Odyssey batteries need only to last about 15 minutes per racing heat, and I will be looking at putting a fresh set in for the next heat. It will cost some this way, but still be much cheaper than the A123's. I've already looked at pricing on them!!! Whew.
> 
> ...


Go to the Controllers Forum and review the thread on the protrotype controller being developed by Tesseract and QER It is in Beta testing now, You can also read about how these guys are really putting a Warp 9 through it's paces. The specs they talk about for this controller make it look like they set out to make a Zilla killer. I think they may have been sucessful.

Your basic ideas sound great and I think with the right components you will have a very competitive ride. The one thing you should keep in mind is that it is going to be expensive.

As far as your battery choice there are guys much better (at the math) then me to go over the pluses and minuses of your selections.

Hang in there and Get Er Dun


----------



## rickeolis (Aug 13, 2009)

Jim,
Thanks again for the news on these two items (Powerglide and the controller).
I have a lot of searching to do and am getting VERY close on looking at ordering a motor.
I'll keep this thread posted!

-Rick-


----------



## DavidDymaxion (Dec 1, 2008)

It sounds like you'll have a fun car.

I'll do the bad news first, but hang in there, then the good news.

An AGM might have around 1000 CA, which means it can pull 1000 Amps for 30 seconds, until down to 7.2 Volts. That means after 30 seconds the battery is putting out 1000 A * 7.2 V = 7.2 kW. A high voltage pack, 30 batteries, would be ~200 kW, or about 200 rwhp. This means that at many tracks you could do the main straight, and then you'd be out of juice. You could putt putt around at 100 kW, but even then it's just 2 or 3 laps. Even if you ignored Peukert effects, at 1000 Amps you'd have 50 Ahr / 1000 Amps = ~ 3 minutes, in real life it's alot less.

Good news, you still have fun alternatives.

My local track has one club that runs events just one lap at a time (the idea is to separate the cars, no fender-to-fender. You do a lap, get in line, and then do another lap, etc. You have 15 to 30 minutes between laps that you could do some charging. You compete via your fastest lap time.

Another option is to bring 2 cars to the track. Run the electric for a lap, maybe 2, put it on the charger, and run the gas car for the rest of your session. Check with your association first to make sure this would be OK.

Another option is autocross. You do low speed (~60 mph) laps of about a minute each, and have some time for charging.

The expensive option: Run lithium, and race for a full 50 miles like the Tesla does! (Although I have heard they'll do thermal cutback when run that hard... Hmm, kind of like my ICE that I have to slow to cool the motor and brakes...).

Some technical comments: The track is a good application for regen, the http://www.proev.com guys get something like 20% more range. You can get more regen if you have front wheel drive or all wheel drive.

Technical comment 2: Keep the tranny! Then you can have a car that has more flexibility for autocross vs. the track vs. a hill climb vs. drag racing vs. drifting vs. the Salt Flats.

Tech comment 3: Keep the clutch! You'll be able to shift alot faster.


----------



## Amberwolf (May 29, 2009)

Another (not necessarily viable) option:

Assuming the 20-30 minutes between laps, make battery boxes that you and your team can pull out of the car and swap whole new pre-charged sets in, just bolt in and tighten the pair of interconnect cables on each set, and go.

That's a pretty expensive way to do it, if you really only get 1 or 2 laps out of each one, depending on how many laps there are, but it could work.

If there are enough laps, and you can pour enough charge into the removed packs over the time they're out to run further laps with them later in the race, then you can use that many less packs. 

It's probably cheaper to do Lithium (and certainly a lot less work!)
________
T_A_S_T_Y live


----------



## rickeolis (Aug 13, 2009)

Thanks very much so far everyone!
I haven't priced lithiums yet, so maybe...
I had planned on having boxed sets of the AGM's to charge between racing heats, but they do need to give me real power for at least 15 minutes. I don't know if the sets of AGM's would do that, and it too expensive to do trial and error to learn, so more reading and talking to pro's first.
TTYL-


----------



## rickeolis (Aug 13, 2009)

Hi again everyone,
One thing I would like to know is whether or not the Advanced 9" motor would work for this application.
If I do direct drive, will I get good enough power for a reasonably fast take-off, but more importantly: Good power up to about 100 MPH?
If I put in a controller that will supply over 350 amps all the time and up to 1000 amps for a short time, should I expect decent driving power with that motor? Or should I look at an 11" motor?
Thanks-

-Rick-


----------



## dimitri (May 16, 2008)

I seriously doubt that 9" will be enough for your racing needs, especially with direct drive.

9" is a good commuter motor, not a racer on a mid size car.

With direct drive if you gear it high enough to get good torque, then you won't see good top speed and vice versa.

You should really check out all the info on this site http://www.plasmaboyracing.com/

This is like a EV racing bible


----------



## dimitri (May 16, 2008)

Hmm, looks like Blue Meanie has single 9" , but it has a transmission.

http://www.plasmaboyracing.com/bluemeanie.php

Also not sure how Datsun's weight compares to your RX7....


----------



## rickeolis (Aug 13, 2009)

Wow thanks- That Blue Meanie is sweet. He is using an Advanced 9" motor but with a tranny. I wonder how often he actually shifts it when racing it.

More research.......

-Rick-


----------



## electricrevolt (Aug 28, 2009)

I too recommend using Lithium batteries, especially if you plan to make replacable packs to change when racing. Besides being smaller, they're also significantly lighter too!

You'll want to get some solid advice on both what total system voltage and amp-hour rated batteries you should use.

For disclosure, I'm a vendor for Lithium batteries and sell them for $1.25 per Ah with a 2-year warranty. But my experience is with commuter cars only, so I can't advise you on a racing setup. -Mike


----------



## rickeolis (Aug 13, 2009)

Wow, it's been a long time since I've logged into this forum to update my project: I built the car using a Warp 9" and Netgain WarpDrive 1200 amp controller.
I began buying a lot of A123 16650 style batteries unitl I had about 300 of them and realized I had a LONG way to go to get the number I would need to make this project work using them...
So, I bought 14 car batteries instead just so I could get the d^%$ car rolling!
Well, it actually works quite well!
I still have a ton of work to do, but I can drive it and it's really sporty.
No gauges at all yet, one racing seat installed, the car has nothing left but a body, wheels, and my EV parts, so it's very lightweight.
I am still working on a charging system; right now I charge the batteries individually with a car charger. I'm shoppoing around for a 165 volt charger...
So far, so good! More to follow-

Rick


----------



## nimblemotors (Oct 1, 2010)

Awesome Rick. Where is the video? 
I was about to suggest you try regular car starting batteries (used ones from junkyard) when reading the thread, because they are cheap and can output lots of power, you will kill them in short order, fun while it lasts. 
But you did it already. 

You can build a cheap manual charger by just taking 120vac and rectifying it, search "bad boy charger". It isn't fast though, towards the end your just skimming the peak of the AC wave.
Would only really do 12 batteries though, not 14, but perhaps you can charge 12 at once, and the other two using a 12v chargers.
This is ghetto-charging, that compliments your pack. 



rickeolis said:


> Wow, it's been a long time since I've logged into this forum to update my project: I built the car using a Warp 9" and Netgain WarpDrive 1200 amp controller.
> I began buying a lot of A123 16650 style batteries unitl I had about 300 of them and realized I had a LONG way to go to get the number I would need to make this project work using them...
> So, I bought 14 car batteries instead just so I could get the d^%$ car rolling!
> Well, it actually works quite well!
> ...


----------



## rickeolis (Aug 13, 2009)

Thanks Nimblemotors-
I hadn't thought about that. I could get the 120 volts to flow in DC with a rectifier and then have it shut off once one of the batteries reaches 12.8 to 13.2 volts... I like it! Then I'd only have to charge 2 more manually.

The other approach I was considering was to adapt my 12 volt car charger to have 12 pair of clamps instead of 2, and wire it in that way...

This is the first time I've driven the car more than a mile, and I'm very happy with it so far. The engine bay is completely empty, it looks cool. I do need to get some pic's and videos!


----------



## Amberwolf (May 29, 2009)

rickeolis said:


> The other approach I was considering was to adapt my 12 volt car charger to have 12 pair of clamps instead of 2, and wire it in that way...


Just don't forget to disconnect all the battery interconnect wires before you do that, or the sparks will be AWESOME.


----------

