another new guy -1st gen Mazda Rx7

3295 Views 6 Replies 4 Participants Last post by NoOther1, Feb 17, 2011

NoOther1

Discussion Starter · Feb 15, 2011

Hi everybody!

My name is Ben, I'm from Montreal in Canada and I'm planning to build my own EV RX-7

I currently own a 3th Gen RX-7 and would like to get a 1st gen since it's a pretty nice car, RWD, and relatively cheap car since almost all of them have blown engines.

I concider myself advanced about mechanic knowledge, My dad's a Professional Mech so I always serviced my car since the age of 16. I'm curently doing a professional formation in body repair

I think that it's good to know that I plan to do this project with a friend of mine who is starting a Bachelor degree in electrical engineering. basicaly, I got hands and he got brains, but I'm pretty confident that I'll learn a lot from this.

I'm hoping to get a 80MPH top speed / 150miles span at cruising speed

here are some things we have concidered so far:

-DC motor
-Li-FePh batteries
-homebuilt controller
-battery recharge on deceleration
-12v converter (to prevent 12v battery+alternator setup)

I'm open to any suggestion/comments. I'm sure you guys will be very usefull.

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dtbaker

· #2 · Feb 15, 2011 (Edited)

sounds great....

as smart as your friend is... consider an off-the-shelf controller FIRST, and see if you can match functionality.

100 mile range very doable, 150 starts getting a little ambitious... unless you have lots of cash and REALLY need the range.

another big disconnect in your specs are that you are only going to get braking regen with AC motor and controller... which drives the price way up with minimal (maybe 10%) increase in range. go simple, go DC, and forget regen for your first project....

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NoOther1

Discussion Starter · #3 · Feb 16, 2011

I'll take that into consideration, a guy already offered me Li-FePO4 batteries

I would say that one of the biggest concern that I have so far is about the drivetrain...

I've read a lot about it already and some are going with "direct drive" setup, some even drive a standard manual transmission. I would prefer a manual TX but would I be able to make the engine spin at 3000rpm to get roughly 65mph ? Should I take a diff with bigger gear ratio ?

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gojo

· #4 · Feb 16, 2011

I have an 83 RX7 conversion. I really like the car. I am running 120 volts LA; 4 in front and 6 in back. I started out with a Chinese BLDC motor with regen. The BLDC motor stopped working last summer, so I am replacing it with a Impulse 9 DC because it is simpler.

I put 175 pound racing springs in the rear, and they were perfect for the extra weight. Stock the car weighed 2500, and the conversion weighs 2700.

I can try to send you some pictures of the set up, if I figure out how, or I can e-mail them to you if you give me your e-mail.

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· #5 · Feb 16, 2011

NoOther1 said:
I'll take that into consideration, a guy already offered me Li-FePO4 batteries

I would say that one of the biggest concern that I have so far is about the drivetrain...

I've read a lot about it already and some are going with "direct drive" setup, some even drive a standard manual transmission. I would prefer a manual TX but would I be able to make the engine spin at 3000rpm to get roughly 65mph ? Should I take a diff with bigger gear ratio ?

No, don't go or bother with direct drive. Use your transmission. You will be glad you kept it. It is more trouble than you know going direct drive. Yes you can but should you is the question. Should you, NO, at least not for your first conversion. What was the offer on lithiums? Be wary. Be careful and ask questions. Can't answer with out specs on what your looking at getting. With DC you should upgrade your brake system if you don't have disc brakes. It is far cheaper to keep your brakes in order than to spend the money on an AC system. If you have unlimited funds then I'd say go for the AC. But not because of the regen. Regen is a nice function and perk of having an AC system. Not a requirement.

Pete

We now have lithiums in our MG.

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Thaniel

· #6 · Feb 17, 2011

Yes Rx7's are great choices as their motors don't last. Any reason you are skipping from 3rd gen all the way to 1st gen for the donor car? I like the 2nd gen's personally. Think they have great brakes and love the indepndant suspension. Seen a few conversions. I needed 4 doors or think that would have been my choice.

Agree with keeping the trans. Even my motor manufacturer says to keep the trans in it's literature. In my conversion I can tell the advantages of being able to shift.

Thaniel

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NoOther1

Discussion Starter · #7 · Feb 17, 2011 (Edited)

Well i really want to keep the twin turbo rotary engine in my 3rd gen. Those engine may cost 2x more gas then any other sports car, i want to keep it that way due to our man/machine relationship.

Can anybody explain how to evaluate my battery cell need ? I would build my own battery packs with headaway-headquarter cells. I guess i should choose my engine and controller before designing my battery packs.

I do know that i have to make enought series to make my voltage go up and meet the motor requirement/potential and that making several "lines" in parallel boost the amps...so if I understand , amps means more travel distance.

Right ?

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