# Planning another Miata conversion



## njloof (Nov 21, 2011)

Marc0, good to see you. Our plans look similar so I will be paying very close attention


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## Ziggythewiz (May 16, 2010)

Welcome Marc0! Curb weight shouldn't be much of an issue with a small amount of A123, what are they, 1 lb each?. Should make for a great low range vehicle.


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## drgrieve (Apr 14, 2011)

To answer the question about the K9 220v - how much power?

Well I guess the answer to that is - For how long? 

My thought is that the Solition Jr is a good match for this motor. Put your 400 A123 into 5p80s configuration and by using liquid cooling to the controller you can see peak of 600 amps. The A123's will keep voltage above 220v at 600amps so you should see 130KW power input to the motor.

More than enough for street use.


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## somanywelps (Jan 25, 2012)

A123's have blistering 20C discharge though... it'd be a shame not to use a soliton 1 and beefier motor.

Can you explain the weight law?

Edit: Here is some math I did for the the motors for my build. "per 2" means dual motors in series. That miata is begging for dual 9"s with a soliton 1 due to that sweet A123 discharge rate.

Plug in Amps for 'x' and you'll get torque IN NEWTON METERS. I did the math down there in FOOT POUNDS.

To be clear:

Soliton 1 (1 motor alone or 2 motors in series)== 1000A

Soliton Jr (1 motor alone or 2 motors in series) == 600A burst (as long as cool, water cooled is long), 500A constant

Soliton 1 (2 motors in parallel) == 500A

True KW power is approx Amps*Volts*.87(eff.)=KW

Kostov 11 250V:

210A 77nm
500A 215nm

0.47586206896551725x + -22.93103448275862

334ft*lb per 1 @1000A
668ft*lb per 2 @1000A
193.67ft*lb per 1 @600A
387ft*lb per 2 @600A
158.57ft*lb per 1 @500A
317.14ft*lb per 2 @500A

Kostov 11 Alpha:
295A 500A
100nm 194nm
0.4585365853658537x + -35.26829268292684

312ft*lb per 1 @1000A
624ft*lb per 2 @1000A
177ft*lb per 1 @600A
354ft*lb per 2 @600A
143ft*lb per 1 @500A
286ft*lb per 2 @500A

K9 220V:

176A 500A
44nm 176nm

Torque=0.4074074074074074*Amps + -27.703703703703695

300ft*lb per 1 @1000A
600ft*lb per 2 @1000A
159ft*lb per 1 @600A
308ft*lb per 2 @600A
130ft*lb per 1 @500A
260ft*lb per 2 @500A

And I don't remember where I read it, but the K9 220V was listed for 600A overload for 10s, so 1000A is probably 5-6s. Do not do it for longer than that.


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## marc02228 (Jan 15, 2011)

somanywelps said:


> A123's have blistering 20C discharge though... it'd be a shame not to use a soliton 1 and beefier motor.
> 
> Can you explain the weight law?


Wow, thanks for posting all the calculations.

Yes, thats exactly my thought. I actually have to use a Soliton 1.

If you convert a car to electric in Germany, the electric curb weight should be at most the same as the original ICE weight. Due to stability of the chassis.
I heard from someone from the TUV, its not a problem, if you are a few kg heavier. But the heavier you get, the more likely you have to do some stability tests.

Thats why I am looking for a donor with a 1.8l engine because curb weight is 1040kg. Does anyone know if the 1.8 Miatas were built without Power steering, too?

Same with the power. The electric power shouldn't be above the ICE power. If I install a K11alpha, and cut back the power at the controller I hope it should be cool. 
I don't know, what they think, if I install 2 motors (even if two smaller ones).

two K9 220V would be an awesome setup, but it's still 20kg more than the K11alpha. 

In the attached picture I did some calculations for acceleration.

I put in a weight of 1150kg. So 1060kg for the car and 90 for me
Didn't find the Area... so I put in 0,645 for Cd*A, but it doesn't make much difference anyway.

0,85 is efficiency of K11alpha. Won't be this efficient at high powers but still better then 100%

One question I asked me, when I saw the plot:
-How does Tesla get an acceleration of 3.9s out of 180kW. The Roadster definitely heavier then 1150kg...


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## Ziggythewiz (May 16, 2010)

Tesla uses a $30K+ battery pack, plus custom everything else. No sane DIYer can match that (though you can beat it for less).

If you're not allowed to exceed the original power, you're probably best off with a single 9". Do you know how they verify that? I would expect them to count your total voltage and controller capacity rather than trust you to limit it in the controller.


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## drgrieve (Apr 14, 2011)

Weird requirements? Just tell them the batteries are rated for max 3C. Lol.

I would think that that could only take the nameplate power of the motor (ie it's continuous rating), not some arbitrary peak power which is really up to the owner to decide what overload that want to put the motor through.

In Australia we also have many requirements to pass - a big one is the 20G crash rating for the battery boxes. But at least the requirements are documented and freely available. Ask for the guidelines in writing. Otherwise if someone verbally gives you advice, make them send you an email so you have it in writing.


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## marc02228 (Jan 15, 2011)

Ziggythewiz said:


> Tesla uses a $30K+ battery pack, plus custom everything else. No sane DIYer can match that (though you can beat it for less).
> 
> If you're not allowed to exceed the original power, you're probably best off with a single 9". Do you know how they verify that? I would expect them to count your total voltage and controller capacity rather than trust you to limit it in the controller.


It's physically impossible to accelerate 1200kg from 0-100 km/h in less than 4 seconds (even with a million $ batterie) with just 180kW
So their motor has to have more power, at least for a short periode of time.


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## Ziggythewiz (May 16, 2010)

My calcs say it requires 116kW to do that. Add in inefficiencies and you're easily around Tesla's numbers.

Also, the motor does not provide the power, the batteries do. The controller converts that power and the motor passes it to the drivetrain.


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## marc02228 (Jan 15, 2011)

Ziggythewiz said:


> My calcs say it requires 116kW to do that. Add in inefficiencies and you're easily around Tesla's numbers.
> 
> Also, the motor does not provide the power, the batteries do. The controller converts that power and the motor passes it to the drivetrain.


hmm, i might have an error in my calculations, then. Here is my calculation method without considering the losses (inefficiencies):
P=F*a 
F=m*a 
a=v/t 

-->P=m*v²/t 
-->P=1200kg * (27m/s)²/3.9s = 224308 Ws/s ≈ 224kW

mmh, I've no idea, what's wrong.. how did you do your calculation?


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## Ziggythewiz (May 16, 2010)

I did kinetic energy = .5MV^2 

If you want a 1200 kg object to be moving at 100 kph it's energy will be 600 * 27.78^2 = 462963 joules (watt-seconds) To give it that much energy over 4 seconds would require 116 kW plus all the losses.


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## somanywelps (Jan 25, 2012)

Being heavier is not a problem if you beef up the suspension. 50kg is like the weight of a person.

Are they going to weight the car or something?

Edit: not exceed original power? F that.

If they are going to test it, just dial in a low amperage on the soliton.

Raise it once you're done.


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## marc02228 (Jan 15, 2011)

Just bought the donor car.
Standart Miata without power steering and another front bumper.
Really good condition


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## Ziggythewiz (May 16, 2010)

Looks great! Is that a swell mid hood (bottom pic)? If so, I believe you're obligated to find a motor large enough to fill it. Maybe a 13"?


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## marc02228 (Jan 15, 2011)

Yes, I probably should do that
But actually can't decide whether to take the Kostov 11 Alpha or the K9 220V right now..


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## marc02228 (Jan 15, 2011)

Could anyone please explain, how one can remove the fuel tank from the car?
Somewhere I read that you have to do it from under the car and take out many other parts. but don't find it anymore...

Gonna pull the engine out, tomorrow.


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## Ziggythewiz (May 16, 2010)

Do you have the car manual? With my bug it was just disconnect the hose inlet and undo a few bolts. The hard part was pouring enough out to make it easy to lift (siphon would have made that easy). With my van you have to lower it, undo top connections, then remove the support straps.


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## galeson (Oct 25, 2009)

evlowrider has a thread on here somewhere where he shows how to take it out through the top. That's the way I did it. I used a reciprocating saw to cut the corners off the tank. Of course make sure it is totally empty in case you cut into the tank.


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## Batterypoweredtoad (Feb 5, 2008)

marc02228 said:


> Could anyone please explain, how one can remove the fuel tank from the car?
> Somewhere I read that you have to do it from under the car and take out many other parts. but don't find it anymore...
> 
> Gonna pull the engine out, tomorrow.


You have to remove the rear subframe to take out the fuel tank. It isn't as daunting as it sounds. You remove the 2 top shock bolts, a single brake line, two big Power Plant Frame bolts, the 4 driveshaft bolts, a couple of clips holding on battery cables and such, and then remove the big bolts holding the subframe up. It shouldn't take more than a couple of hours to get the tank out. While you have the subframe out I would suggest replacing the suspension bushings. Any Miata that age has completely worn out suspension bushings.


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## marc02228 (Jan 15, 2011)

Some nice progress, today.
Motor, exhausting system and fuel hoses are out.

I might use the K9 220 if everything goes well, i can install a 2nd K9. should I take the 220V or the 144V, then? 
Didn't really thought about using two motors, before.


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## drgrieve (Apr 14, 2011)

Use the Dual K9 that comes pre-built in that case. This way you don;t have to couple them yourself.


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## marc02228 (Jan 15, 2011)

Actually nothing new, here. But I finished designing the PCB for the batteriepack.
I will build the Pack out of nine modules à 10s3p and one module 6s3p.

If anyone needs a PCB, let me know. I had to order a couple more, than I needed to get a reasonable price.

This is what the design looks like as a 9s3p version.


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## kerrymann (Feb 17, 2011)

galeson said:


> evlowrider has a thread on here somewhere where he shows how to take it out through the top. That's the way I did it. I used a reciprocating saw to cut the corners off the tank. Of course make sure it is totally empty in case you cut into the tank.


I pulled mine from the top but if I were do it again I would do it from the bottom. You have to pull the rear sub frame but it's a good time to replace all of the old suspension bushings.

http://www.miata.net/garage/fueltank.html

BTW nice looking donor! You got a great start on a conversion!


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## marc02228 (Jan 15, 2011)

Finally the PCB's arrived
All fits well and looks pretty


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## marc02228 (Jan 15, 2011)

Does anyone know, how many pulses per turn the original Miata tach expects?


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## marc02228 (Jan 15, 2011)

Still testing all the cells. 
278/400 done. I'm gonna use 96s3p, so I actually just need to test 10 more cells, but I wanna pick out the best and actually have some time left for the cells.

Removed the dash board, took out all the unnecessary Miata wiring harness and added some new cables.

Because I am to tall for the original seats, I bought some Elise MK2 seats which are almost in. Just need to optimize a bit.

Today I picked up motor (K11Alpha), controller (Soliton 1) and other components. Hope to finish the main work at the car in August...

Next steps:
-finish seats
-remove fuel tank
-install motor
-put the car on scales to keep weight distribution
-keep testing cells
- etc. pp.

I am not sure, whether to mount the motor directly to the chassis or to use stock rubber damper. I've seen both. 
Any suggestions, what's better?


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## Ziggythewiz (May 16, 2010)

Stock mounts are good to keep vibrations/noise down.


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## cpct (May 31, 2012)

marc02228 said:


> -BMS (don't know which one, since i need a EMI certificate for it) actually I
> wanted to use Orion or EMUS.


We are also converting a Miata and have chosen the Electromotus/EMUS BMS. It is not cheap but the software and support is really good. After some issues with the top/bottom modules, replacements were sent right away. Not sure about EMI conformance though. Having it tested at a qualified lab can be very expensive (+1000 EUR)


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## marc02228 (Jan 15, 2011)

> Stock mounts are good to keep vibrations/noise down.


That was my thought, too. But I am not sure, if it can handle the torque, even though most of it should be transferred by the motor/Gearbox adapter.?



> We are also converting a Miata and have chosen the Electromotus/EMUS BMS. It is not cheap but the software and support is really good. After some issues with the top/bottom modules, replacements were sent right away. Not sure about EMI conformance though. Having it tested at a qualified lab can be very expensive (+1000 EUR)


I ordered the EMUS BMS a couple days ago. Good to hear, that it works well. 
What diameter are the connecting holes for the cells? How long are the cell units (A/B)? I am not sure if it fits to my A123 Modules. Maybe I have to cut off the connecting holes and connect it by cable or connect the cell units by some L-bracket or so.


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## cpct (May 31, 2012)

marc02228 said:


> That was my thought, too. But I am not sure, if it can handle the torque, even though most of it should be transferred by the motor/Gearbox adapter.?
> 
> 
> 
> ...


I can't check right now, but the holes are at least M6 (the thread size on our ThunderSky cells) and the dimensions according to the manual are 50 x 30 x 17 mm The modules are designed to fit prismatic cells mainly so some "hacking" will be needed for your setup.

An L-bracket seems the best for warranty


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## kerrymann (Feb 17, 2011)

marc02228 said:


> That was my thought, too. But I am not sure, if it can handle the torque, even though most of it should be transferred by the motor/Gearbox adapter.?


Make sure all the torque is taken by your motor mounting. The transmission is designed to hang from the motor and react all the torque their. That small ladder channel that goes to the rear axle won't take any real torque. If you are unsure I would add a rod from one of the front motor 3/8" bolt holes tangentially to the frame. I went with direct mounting as these motors have virtually no vibration but only time will tell if my choice was a good one.


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## marc02228 (Jan 15, 2011)

Cell testing is done, half of the packs are assembled.

yesterday I connected the rebirth adapter to the motor and flywheel and run it at 24V on the soliton. 
There seems to run rough. It's not vibrating, but you see it, when you take a close look or try to mark it with a pen. I don't know, why this is.

I guess, its time to post some pictures...

The motor is the Kostov Alpha.


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## marc02228 (Jan 15, 2011)

*Fuel Tank... OUT*

This afternoon, I took out the fuel tank. 
Wasn't that hard, as I assumed it would be.

I removed the rear subframe and took it out. The only problem was that the nut of one of the lower arm of the suspension, which originally is welded to the arm wasn't welded anymore and is REALLY hard to reach. So it took some time to get it out and to get the screw fixed afterwards.

Now I am waiting for my motor and controller to be back, which are at a machinist, who hopefully fixes the rough running flywheel.


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## giless (Jul 23, 2011)

Great looking battery packs. How much are your boards? Am looking at a similar conversion with an RX8 but I think I will be needing 6 or 7p A123 cells.


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## marc02228 (Jan 15, 2011)

Thanks.
The Boards were around 30 Euro each. 
You could use a copperbar to connect 6 or 9 in parallel, but I am not sure about the resistance, then.



giless said:


> Great looking battery packs. How much are your boards? Am looking at a similar conversion with an RX8 but I think I will be needing 6 or 7p A123 cells.


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## zeroexcelcior (Aug 2, 2011)

marc02228 said:


> Does anyone know, how many pulses per turn the original Miata tach expects?


From what I understand, for all four stroke ICE, a tachometer expects half the number of cylinders to fire per revolution of the crankshaft, so two pulses per turn for your conversion (stock inline four) but get a second opinion just to be sure.

Best of luck.


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## Batterypoweredtoad (Feb 5, 2008)

A generic motor mount with a stud protruding from each side would work fine in the Miata stock mount holes or in holes drilled in the front crossmember. I would use some sort of cushioned mount as several people here have reported a whining or singing noise when direct mounting their motors. I don't think the power plant frame will give you any issues.

K11 Alpha? With a pack that can feed it? I am excited to see what this thing will do! Please get it to a dyno or dragstrip as soon as you can and post the results and log files.


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## marc02228 (Jan 15, 2011)

Some progress, again.

I cut holes for the battery boxes into the trunk floor and where the fuel tank used to be. So I can split the pack into smaller packs to get the best weight distribution possible and for some additional space.

With the motor connected to the adapter plate I noticed that the flywheel can be turned almost 2mm without any turn of the motor. When I assembled motor and adapter plate I measured a gap (for the feather key) of 6.5mm and the motor has gap of 6.1mm so I tried to make a feather key myself but it apparently didn't work out.

Now I gave motor and adapter to a relative to make a CNC feather key. So I still can't work on the motor mount. 

Some other thing I noticed is that the Rebirth adapter plate doesn't fit the manufactured mounting platforms of the Kostov Alpha. No matter, which 4 of the 8 holes you take, the motor is attached twisted and not parallel (the platforms) to the subframe. 

So If you use a Kostov Alpha I would definitely not take the Rebirth adapter. It looks good, and is is really good manufactured, but bad engineered.

Now I tried to setup the Audi vakuumpump I bought for the conversion. Seems to work good, but the vakuumswitch I bought can only put out a current of 100mA which is not enough for a 12V relay. Tried a 20A relay, too. But it doesn't work either (even though it just takes 70mA). Maybe the initial current is to high?

Just ordered another vakuum switch. I could use an even smaller relay to drive the power relay, but I don't wanna do this in the circuit of the vakuumpump for the brake.

Today the EMUS BMS was shipped. The motor shall be back the next couple days and battery boxes should be done until the weekend, too.

Does anyone knows how the fuel (and oil pressure and temp) gauge works? Does it need a signal 0-12V or a varying resistance to the ground or whatever?


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## marc02228 (Jan 15, 2011)

After three weeks, I am finally back home, to continue working on the car for 3 days. 

The new feather key works great. No slackness anymore between motor and hub.

The clamp (part of the motor mount) looks really good, too. Now I have to figure out, how to connect it to the subframe or the original motor mounts at best. 
Any Ideas?

BMS arrived, but some components of it are still missing.
Batterie boxes aren't done yet.

I figured out, how the original fuel gauge works.
It has two magnets. One, which puts the gauge back to zero, if 12V is connected and the other magnet has to be set by the sensor/BMS. 
If both magnets are the same field strength, it will stay in this position.
I set up a small circuit to get it driven by the BMS but still have to order the parts and test it.


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## tylerwatts (Feb 9, 2012)

Marc

Very impressive build spec! How are you fitting hte Alpha in there? Are you lifting the entire motor/transmission and torsion arm up at an angle to clear over the top of the steering rack? I see there's clearance in the tunnel, but how is the rear differential and mounts taking this twisting? The mounts are rubber, so should be ok if in good condition, but I don't think the rear mount will like it, adn that cast aluminium is a bit brittle so dropping a lump of torque through the drivetrain (as I expect you and e all want to see, hence the mighty spec you have) could flex the arms of the diff too much and possibly fracture one of them. Just a thought.

I have been thinking about and researching a similar conversion for my Eunos, but looking at an American Powerglide 3spd auto without torque converter since that motor certainly doesn't need alot of gears! Looks liek the Alpha is nice and short and should move back enough to remain horizontal behind the cross member with that set-up. Hard to tell how I'd connect the torsion beam though, might get away with the transmission being shorter without the torque converter and only 3 gears and adapt the gearbox with a mating point for the standard torsion arm.

Why did you decide to keep the standard transmission?

Thanks
Tyler


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## JetPack (Oct 1, 2012)

Looks good Marc.. that motor fits with ease.. could go larger? haha

What is the power on that motor? I think I seen about 150hp on the K11 Alpha? Is that right?

Im doing a dual motor Rx7 FC... hoping I have enough power to break stuff.


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## marc02228 (Jan 15, 2011)

tylerwatts said:


> I have been thinking about and researching a similar conversion for my Eunos, but looking at an American Powerglide 3spd auto without torque converter since that motor certainly doesn't need alot of gears! Looks liek the Alpha is nice and short and should move back enough to remain horizontal behind the cross member with that set-up. Hard to tell how I'd connect the torsion beam though, might get away with the transmission being shorter without the torque converter and only 3 gears and adapt the gearbox with a mating point for the standard torsion arm.
> 
> Why did you decide to keep the standard transmission?


I couldn't decide if I wanna keep the transmission or get rid of it. 
I decided to keep it at first, to get it approved, road legal and to test, how it works just driving in 4th gear (ratio 1:1) after that I might test to go without transmission.

I had to lift the transmission by 1cm or so, due to the diameter of the motor.. I think, that should be ok.
The length of the motor fits perfectly, just had to remove the cooling fan to get the motor with flywheel and clutch into the bellhousing.


@JetPack
The motor is actually a bit longer, because the cooling fan is removed.
The nameplate of the motor says 45kW, but it should be able to put out some more power than that


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## tylerwatts (Feb 9, 2012)

Good plan Marc

A not eon the transmission, guys turbo them past 250BHP so they're strong, only thing is the Turbo Lag saves the transmission as it loads up the torque smoothly. Make sure you set the Soliton's torque ramp up gentle, it'll still be more than any ICE but will give ht transmission a nice time of it and save throwing away gearsets! I'm keen to hear what performance you get with 4th! Be nice to lose the transmission, though for my use I'd want at least 2 speeds (city/motorway) to maintain reasonable motor efficiency. Just a point to note. You could play with using both 2nd and 4th, and mioght want to limit torque in 2nd (through something like a reversing switch on the gate for 2nd to talk to the controller) as that motor will delaminate your tyres pretty quickly with those ratios!


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## dtbaker (Jan 5, 2008)

marc02228 said:


> Now I tried to setup the Audi vakuumpump I bought for the conversion. Seems to work good, but the vakuumswitch I bought can only put out a current of 100mA which is not enough for a 12V relay. Tried a 20A relay, too. But it doesn't work either (even though it just takes 70mA). Maybe the initial current is to high?


sounds like your switch cannot put out enough to energize a standard automotive relay, they typically need about 200mA to hold the coil. You might want to consider using SSR relay. The 'crydom d1d12' SSR only required about 15mA to trigger; retail for about $50, and on ebay about $22


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## marc02228 (Jan 15, 2011)

dtbaker said:


> sounds like your switch cannot put out enough to energize a standard automotive relay, they typically need about 200mA to hold the coil. You might want to consider using SSR relay. The 'crydom d1d12' SSR only required about 15mA to trigger; retail for about $50, and on ebay about $22


Thanks for the advice regarding the vacuum switch. But I've already a new switch which is able to put out a higher current and has a 2nd output (analog) which I will use to check the vacuum while driving.

Had some great progress at the car the 4 days I was at home.
Motor mount is done. I used the holes where the original motor mounts were located and the three holes in the subframe.

Motor, Flywheel and clutch are finally assembled and build into the car.

I couldn't resist and connected the controller to test drive the car using one of my Batterie modules (33V, 60Ah)

I actually had no time because I had to go back to Cologne, so I used all the parts lying around in the garage. 

6mm^2 cable for the Controller - Motor connection
1.5mm^2 cable for Batterie - Controller connection 
and controlled the throttle pot by hand to accelerate the car.

I chose a really soft Soliton Setup, because it was the first drive and the extremely undersized cables. 
Slew rate: 100A/s
Max amp: don't remember, but almost as low as possible 

The result was.. well, it was driving and I was happy, but as slow as expected. The 1.5mm cables just were a little bit warm, so I put in a 2nd batterie module to have a voltage of 66V, increased the max current and slew rate step by step.
Don't remember the current but in the end the slew rate was enabled to 1000A/s.

Well... then it was fun to drive. Wheels were loosing grip in reverse, which really surprised me. 

Hopefully I will be able to continue working on the car, in 2-3 weeks.


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## dtbaker (Jan 5, 2008)

marc02228 said:


> I had to lift the transmission by 1cm or so, due to the diameter of the motor.. I think, that should be ok.
> The length of the motor fits perfectly, just had to remove the cooling fan to get the motor with flywheel and clutch into the bellhousing.


I have very little clearance between motor body and steering rack with my Warp9. Also have very little clearance between tailshaft tach pickup and torsion bar. You only had to lift by 1cm for your 11" motor? Any close-ups of your motor mount? Solid, or rubber?

can you say a little more about what you had to do with cooling fan? you removed it? just for installation? are you going with forced air with external fan thru input?


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## marc02228 (Jan 15, 2011)

Some progress I missed to share is the my solution of the Music/navigation unit.

The place, where the ECU used to be is now used by a small Alpine amplifier I bought on ebay for 20 Euro. A Samsung Android 7" tablet is connected to it. The tablet still needs some frame around it, but it works great. 
When you turn the ignition key on, it starts the EMUS BMS GUI and doesn't go in standby mode.
When you turn the the car off, it shows a clock for a minute and then goes in standby mode. 

One thing I don't like is, that I have to control the volume with the touchscreen.


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## marc02228 (Jan 15, 2011)

dtbaker said:


> I have very little clearance between motor body and steering rack with my Warp9. Also have very little clearance between tailshaft tach pickup and torsion bar. You only had to lift by 1cm for your 11" motor? Any close-ups of your motor mount? Solid, or rubber?
> 
> can you say a little more about what you had to do with cooling fan? you removed it? just for installation? are you going with forced air with external fan thru input?


I just removed it for the installation. It's back on the motor now. 
I had to loosen 4 screws (two left and two on the right) of the bar in front of the motor (anti roll bar??) to mount the forced air fan. Didn't have to remove the bar completely, just pushed it down a bit and I was able to get the fan back on the motor.


EDIT:
I put 6mm rubber between Motor mount and subframe, but the screws are tightening the rubber, too.

This is currently the best picture of the mount. The ring is welded to the U-Profile.


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## dtbaker (Jan 5, 2008)

interesting..... It looks like the Warp9 is longer! Note the tailshaft+tach pickup are within an inch of torsion rod on mine.


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## kerrymann (Feb 17, 2011)

Congrats on driving under lithium power! I like where you put your android tablet.  

For the volume control on your stereo I recommend this inbetween the 3.5mm output of the tablet and the input of your amp.

http://www.bhphotovideo.com/bnh/controller/home?O=&sku=772649&Q=&is=REG&A=details


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## marc02228 (Jan 15, 2011)

@Kerrymann
Thanks for the advice. I think I'll try it this way.

I am back home for a couple days. 
Installed a new/used flywheel and the original miata clutch. Now it drives smooth. It seems, that the aluminum flywheel has some kind of imbalance.


Set the Soliton to max. power of 40kW with bigger cables @100V. It's really fun to drive.

Next steps:
-Install battery boxes
-get the controller rack done and final assembly of the drivetrain
-put the car on scales to check the weight distribution


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## marc02228 (Jan 15, 2011)

The last couple days, I got all the things on the to-do-list done.

Batterie boxes are temporarily in(need some more L-brackets).
The controller is attached to adapter plate and motor mount and I drove the car around 6km to the scales.

Weights are with 4,6 of my A123 modules (46S3P) and a 74Ah Lead batterie (~18kg) for the 12V supply.

Total weight: 950kg
Front weight: 470kg
Rear weight: 470kg

10 kg are missing somewhere, thats the tolerance of the scales.

3 modules (16kg each) are in the trunk and 1,6 modules are where the passenger seat used to be. 

The lead batterie is in the fuel tank area.

So I think, that are pretty good news.

Some pictures:


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## marc02228 (Jan 15, 2011)

Today I installed the pulse divider to get a 2 pulses per revolution signal out of the 80 ppr of the ball bearing sensor of the K11 Alpha.
After a few problems and an hour of playing with the scope, all works fine.

Now the RPM are limited to 4500 RPM and the tachometer can work with that signal, as well.

And I took a couple videos. 
Video 1
Video 2

Password for the videos is: test

The speed looks a bit faster, because of the wide angle camera.

If anyone is interested in the RPM Reducer, I've four PCB's, boxes and components left. 
If you want the schematics, just send me a PM with your mailaddress.


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## PTCruisin (Nov 19, 2009)

Very nice! I enjoyed the videos. I am working on my second conversion which is a 1990 Miata. Can you explain where you connected the tach signal? Did you simply replace the crankshaft position sensor with the signal you generated or did you connect your signal to the tachometer directly?

Ralph


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## marc02228 (Jan 15, 2011)

PTCruisin said:


> Very nice! I enjoyed the videos. I am working on my second conversion which is a 1990 Miata. Can you explain where you connected the tach signal? Did you simply replace the crankshaft position sensor with the signal you generated or did you connect your signal to the tachometer directly?
> Ralph


I just connected the 2 PPR signal directly to the tachometer by a shielded cable.


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## PTCruisin (Nov 19, 2009)

marc02228 said:


> I just connected the 2 PPR signal directly to the tachometer by a shielded cable.


Good to know. Danke!


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## dtbaker (Jan 5, 2008)

marc02228 said:


> Today I installed the pulse divider to get a 2 pulses per revolution signal out of the 80 ppr of the ball bearing sensor of the K11 Alpha.


WHERE are you pulling the 80 ppr original signal from?

most people just use an optical or Hall effect sensor on the tailshaft, but I am interested more for my Swift where I don't HAVE room for a tailshaft. I could potentially pick a signal up off the starter ring gear, or perhaps something else on the motor hub internally.....


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## marc02228 (Jan 15, 2011)

dtbaker said:


> WHERE are you pulling the 80 ppr original signal from?


The Kostov Alpha has a built in rpm sensor, which produces the 80 pulses.


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## Lipo Louis (Oct 29, 2012)

Very helpful and interessting thread, looking forward to the updates.

You have a 96s pack, you charge to 3,54v per cel ? So you do not exceed the 340V for the Soliton1 ? Or do you charge to 3,60v ?


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## marc02228 (Jan 15, 2011)

Lipo Louis said:


> Very helpful and interessting thread, looking forward to the updates.
> 
> You have a 96s pack, you charge to 3,54v per cel ? So you do not exceed the 340V for the Soliton1 ? Or do you charge to 3,60v ?


I'm not sure about that, yet. I think I'll just charge to 3,55V or even 3,5V the difference will probably be small and it's better for the cells.

The absolute max. voltage of the Soliton is 342V. And even if you charge to 3.6V the voltage will probably drop below 342V after a moment when the charger is removed. But that's something I'm gonna have to test.


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## drgrieve (Apr 14, 2011)

One of latest software release bumped up the max voltage to 350V.

What is the maximum voltage I can run with a Soliton controller?
The limit recommended in the manual is 340V for the Soliton1 and Soliton Jr, and 425V for the Soliton Shiva (actual voltage, not "nominal", since nominal has no formal definition). The actual limit (displayed in the web interface) for the Soliton1 and Soliton Jr controllers is 350V, but that is to accommodate inevitable errors and drift in the voltage measurement circuit - after all, these are motor controllers, not lab grade measurement instruments, so allow for at least 2% error in voltage and current measurements!

Also note that the maximum motor current limit is reduced to 900A in the Soliton1 and 500A in the Soliton Jr any time the battery pack voltage is above 310V. The Soliton Shiva has no derating with voltage.


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## marc02228 (Jan 15, 2011)

drgrieve said:


> One of latest software release bumped up the max voltage to 350V.
> 
> What is the maximum voltage I can run with a Soliton controller?
> The limit recommended in the manual is 340V for the Soliton1 and Soliton Jr, and 425V for the Soliton Shiva (actual voltage, not "nominal", since nominal has no formal definition). The actual limit (displayed in the web interface) for the Soliton1 and Soliton Jr controllers is 350V, but that is to accommodate inevitable errors and drift in the voltage measurement circuit - after all, these are motor controllers, not lab grade measurement instruments, so allow for at least 2% error in voltage and current measurements!
> ...


Ok, I didn't know about the bumped up limit to 350V. Thanks.


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## Lipo Louis (Oct 29, 2012)

About the A123 cels, are the allowed for building a EV battery ? I know since april 2011 the EU changed some regulation to register an EV for public road like a EMC marking for the controller etc.

And for the batteries you have to build solid boxes ofcourse, but no questions asked for CE marking or something else ? Insurance companies also won't ask ?

I can imagine that if a house will burn down with some homemade China RC lipo's EV battery that a insurance company can be tough.


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## marc02228 (Jan 15, 2011)

Lipo Louis said:


> About the A123 cels, are the allowed for building a EV battery ? I know since april 2011 the EU changed some regulation to register an EV for public road like a EMC marking for the controller etc.
> 
> And for the batteries you have to build solid boxes ofcourse, but no questions asked for CE marking or something else ? Insurance companies also won't ask ?
> 
> I can imagine that if a house will burn down with some homemade China RC lipo's EV battery that a insurance company can be tough.


There is a huge difference between LiFePO4 and LiPO batteries. I think it will be VERY hard to get a car with LIPO batteries approved in Germany, but with the A123 it should be possible if you build them into good and solid modules.


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## marc02228 (Jan 15, 2011)

the picture shows the almost final cell Module. I've some Capton tape here to cover the edges of the cells, but at the moment I don't see any reason to do so, does anyone?
The 0,2mm Mylar sheets are quite strong and even fit between the tabs of the cells.

Module specs: 
-Voltage: 33 V (nominal)
-Capacity: 55,5 Ah (measured)
-Max. discharge: 1200A
-Weight: 16kg


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## marc02228 (Jan 15, 2011)

Some news, here.

I finished all of the batterie modules and connected the BMS.
Since I drove different distances with the modules, the BMS had to balance the pack for almost 2 days. But that's fine, because I think I drove 2 modules down to almost 50% SoC while others would have been around 80% or so.

I finally put in the Elise seats, but have to remove them and use the original Miata seats, otherwise I won't get the car approved.
They actually fit really nice into the car.

The clutch will be removed to get rid of all these mass, that has to be accelerated and to keep the weight of the car down. Now, that I have to use the heavy Miata seats the weight will get very tight. It must not exceed 1230kg with 150kg for the driver and passenger so 1080kg (minus 10kg or so for luggage) for the whole car. That might be a spot landing.

Since I use the EMUS BMS and it already comes with a nice Android app, we modified the app (just in a simple way) to send the data (link) to the internet in an adjustable interval. 
The history will also be saved, so one can easily generate a graph from it.

Does anyone know, how to put in a "°C" (as unit) in a PHP code, to be shown correctly on the webside?
If anyone is interested in the modified app just send me a message with your mail address.

I have to stop doing all these unnecessary things and get the car to the road.


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## dtbaker (Jan 5, 2008)

you can't change the SEATS and pass inspection?! crazy rules!

on that topic though, I am considering changing my seats out for some fixed race buckets to save weight and because the leather in the OEM is pretty badly cracked. But it was looking very expensive very fast with seats, base, sliders... like over $400 per seat. Did you do it for less? did you need a different base for the Elise seats? do you know what they weigh?


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## marc02228 (Jan 15, 2011)

dtbaker said:


> you can't change the SEATS and pass inspection?! crazy rules!
> 
> on that topic though, I am considering changing my seats out for some fixed race buckets to save weight and because the leather in the OEM is pretty badly cracked. But it was looking very expensive very fast with seats, base, sliders... like over $400 per seat. Did you do it for less? did you need a different base for the Elise seats? do you know what they weigh?


Yes, it has to be adjustable (front-back) and the back of the seat or if you have a bucket seat the whole seat has to be 15° adjustable. 

I did pay 400Euro for used and a bit dirty MK2 seats. 

I did the adapter myself. Here are some examples.


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## marc02228 (Jan 15, 2011)

Couldn't do anything else the last two days, so I tried to edit the videos of some test drives to one with music 
Video


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## Lipo Louis (Oct 29, 2012)

Haha NICE !! Seems to be pretty quick isn't it ? And that with just 60kw !


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## marc02228 (Jan 15, 2011)

It looks a little bit faster due to the wide angle of the camera. 
But I think it's actually less then 60kW because of the voltage drop at the tiny 10qmm wire.

Edit: but it's fun to drive


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## dtbaker (Jan 5, 2008)

very artistic music. 

I am hoping to get some sort of camera soon, and be able to do some basic editting to get clips up on youtube. I want to have at least a 'walk-around' the car, and an 'over the shoulder' view showing tach/speedo and view from the drivers seat while driving.

I'm planning on making several runs on a specific length of road at various amp limits and trying to show 0-60 mph performance vs amp limits.... something like that would have helped me decide between soliton jr (600amp), soliton 1/zilla(1000amp).

any recommendations for SIMPLE videocam + .mpg edit software?


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## marc02228 (Jan 15, 2011)

dtbaker said:


> very artistic music.
> 
> I am hoping to get some sort of camera soon, and be able to do some basic editting to get clips up on youtube. I want to have at least a 'walk-around' the car, and an 'over the shoulder' view showing tach/speedo and view from the drivers seat while driving.
> 
> ...


I have an old GoPro HD Hero (1) which I bought for holiday a couple years ago. I mounted it to the area, where the radiator used to be (by one M6 bolt). It's a 5 min setup

I've no idea, which other camera you could use , because I actually never thought about making videos.


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## marc02228 (Jan 15, 2011)

It's time for a short update. 
Finally all the big power cables are in the car. The 3rd battery box is done and all boxes are painted and finally in the car, as well. I finished the Android tablet installation and the switch console in the middle between the seats. 
The left switch is the start switch. The key switch is for valet mode, the thing in the middle is a pot for volume control of the tablet. The big red switch is the emergency stop

The next days I'll install all batterie modules, finish the wiring and hopefully do some serious test drives.


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## njloof (Nov 21, 2011)

That switch panel looks great. Did you just yank the cup holders and put in a piece of carbon fiber? Where do you put your latte?


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## marc02228 (Jan 15, 2011)

njloof said:


> That switch panel looks great. Did you just yank the cup holders and put in a piece of carbon fiber? Where do you put your latte?


The car had no cup holders. I yanked out the ashtray and cut out the piece of plastic which was screwed to the tunnel where the cardan shaft runs. Now the carbon fiber plate is screwed to the tunnel and holds the center console.
Hopefully one doesn't need caffeine in the car


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## marc02228 (Jan 15, 2011)

Damn, that thing is fun


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## Lipo Louis (Oct 29, 2012)

Well' any updates ? Did you use the a123 with the emus BMS, is everything working OK ?


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## marc02228 (Jan 15, 2011)

I am actually spending a lot of time at the car, at the moment. 
But you don't see much progress. I am mainly doing stuff to get it road legal. So many small changes.

Tomorrow, I'll probably pick up a 5-day license plate, for which the car hasn't have to be approved by the TUV, to test how the car behaves, if I would go clutchless and to test everything else.

BMS and Cells work fine together, but only have done a few cycles.

Yesterday, I finally mounted the bluetooth module of the BMS (using the glue pads, which came with it). Before I had no problems with the bluetooth connection, but now it's disconnected most of the time...
Murphys Law, I guess

And I got my new wheels. OZ Superleggera. They are really super light. Below 5kg each rim plus the bald tire
So I save 15kg for the car, which I needed to get the total weight down plus less rotating mass.


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## marc02228 (Jan 15, 2011)

Ta-dah! The new super wheels


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## Lipo Louis (Oct 29, 2012)

Ok, that sounds good, good luck with the car and approval.

Did you keep the original flywheel ? I was thinking to make it lighter.


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## marc02228 (Jan 15, 2011)

Lipo Louis said:


> Ok, that sounds good, good luck with the car and approval.
> 
> Did you keep the original flywheel ? I was thinking to make it lighter.


I have a lighter wheel lying around. Sooner or later I will replace the stock flywheel. 
But I first have to decide whether or not to replace the clutch or remove it completely, because it slipps like hell...


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## marc02228 (Jan 15, 2011)

Collected my temporary license plate last Friday. The MX-5 drove about 200km since then, without any problems. Ok, the Emus BMS current sensor doesn't work reliable since two days, which is a bit annoying to estimate the range. 

The first day it was actually quite cold. Just above 0°C outside. The range was 65km plus some reserve, which I didn't use.
And it was hard to keep the foot from the throttle. So there may be another 15km or so.


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## marc02228 (Jan 15, 2011)

The Kostov RPM sensor bearing broke down after just 10h of work or so... 
So we had to find another way to read the RPM, which was not too easy because the cooling fan is not connected to the shaft (it has an extra 12V motor) and there is not much space, because of the fan.

In the end, we used a small 5mm inductive sensor and an aluminum "propeller". Fits perfectly between fan and motor and gives a reliable signal.

Carpet is in, some insulation added. Hopefully we get the BMS current sensor next week, so it can finally get the approval...

We still need a name for the car.. any suggestions?


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## marc02228 (Jan 15, 2011)

The car has been approved by the German authorities, yesterday. So we are not only ready to drive on the streets, but also allowed to


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## dtbaker (Jan 5, 2008)

marc02228 said:


> I have a lighter wheel lying around. Sooner or later I will replace the stock flywheel.
> But I first have to decide whether or not to replace the clutch or remove it completely, because it slipps like hell...



I have a 'heavy duty' (Exedy) clutch in my miata... doesn't seem to slip w/ Warp9, Zilla pulling 1000 amps @156v nominal.

I dunno if it would be enough for an 11" motor though...


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## dtbaker (Jan 5, 2008)

marc02228 said:


> Ta-dah! The new super wheels


very cool wheels..... looks like they run about $300 each though; yikes! Did you get a deal?

what size/offset did you order to match the Miata?


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## Woodsmith (Jun 5, 2008)

marc02228 said:


> The car has been approved by the German authorities, yesterday. So we are not only ready to drive on the streets, but also allowed to


Well done!


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## kerrymann (Feb 17, 2011)

marc02228 said:


> The car has been approved by the German authorities, yesterday. So we are not only ready to drive on the streets, but also allowed to


Congrats again on getting it street legal! Have you done any range and performance tests (0-60)?



marc02228 said:


> I have a lighter wheel lying around. Sooner or later I will replace the stock flywheel.
> But I first have to decide whether or not to replace the clutch or remove it completely, because it slipps like hell...


I think we have same clutch which is rated at ~250ftlbs and I can slip mine a little but I am only running a 9" at 800A+150V. Trying to get a clutch to handle a 11" is going to be expensive. I have been looking for a better one if I am going to throw in my second 9". I found a few with +500ftlb rating but they are $1000-1500 for just the disc and pressure plate. The 400 ftlbs go for about $500 which is probably enough for your 11.


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## marc02228 (Jan 15, 2011)

I think I'll just keep the clutch this summer and order a better one for next year. 
This one might be good.

The wheels are OZ Superleggera 7Jx15, weight is under 5kg. Offset is 30. The old wheels offset was 37. I bought them 2nd hand. The seller said, he paid 600 Euro each (for a complete tire). I paid 550Euro for all four, which was quite a good deal.
Unfortunately, OZ doesn't manufacture this rim anymore.

Hmm, I didn't really test the car, yet. Range will be around 100km. 
I did some quick acceleration tests, of course
Now with the chronically ill clutch it's a bit above 5s.

Before I weakened the clutch, the acceleration was insane. I was able to spin the (old)wheels at 60 or 70km/h.
Weight of the car is 1080kg. 560 at the rear axis.

I think the insulation between the cells does a good job. I only had one dead cell, yet. This cell died at the 2nd cycle.


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## marc02228 (Jan 15, 2011)

A few pictures of the almost finished car. There is still some work in the trunk to do.


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## marc02228 (Jan 15, 2011)

another try...


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## marc02228 (Jan 15, 2011)

Batterypoweredtoad said:


> A generic motor mount with a stud protruding from each side would work fine in the Miata stock mount holes or in holes drilled in the front crossmember. I would use some sort of cushioned mount as several people here have reported a whining or singing noise when direct mounting their motors. I don't think the power plant frame will give you any issues.
> 
> K11 Alpha? With a pack that can feed it? I am excited to see what this thing will do! Please get it to a dyno or dragstrip as soon as you can and post the results and log files.


The car hasn't been on a dyno yet, but here's a Soliton log. It's recorded in the 3rd gear, 100km/h (60mph) would be equal to 5400 rpm and the motor is limited at that speed. The tach signal is very noisy, will try to put in a lower pull down resistor. 
In the test run, the current was cut off at around 90km/h, due to the noise.

Motorcurrent: 900A 
Slewrate is 1000A/s
Motorvoltage: 250V
The clutch doesn't like anything above that in 3rd gear. In 4th and 5th it's much worse, of course.

The right y-axis is for RPM, the left one for all the other values...


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## Lipo Louis (Oct 29, 2012)

About 225 kW input power, and 4.8sec to 90 kmh ?
Your car is a beast !! What is the weight ? About 1100 kg ?


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## Batterypoweredtoad (Feb 5, 2008)

Wow! If I am reading that correctly you have a 4000+ RPM range with 290 ft lbs of torque. That pack, controller, and motor seem really well matched.


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## marc02228 (Jan 15, 2011)

Lipo Louis said:


> About 225 kW input power, and 4.8sec to 90 kmh ?
> Your car is a beast !! What is the weight ? About 1100 kg ?


The car weighs 1080 kg + 90 kg for me is 1170 kg when I recorded the data.
I wonder, why there are 225 kW shown in the diagram, I actually limited the Soliton to 210 kW.

Just did some quick math.. the average rpm rise per second is 1342 (rpm/s).
5440 RPM is equal to 100 km/h in 3rd gear.
With the rpm rise per second the car should be at 100 km/h in 4.1 s, in the best possible case. 

To get closer to that value I will:
-modify the RPM sensor to get rid of the noise
-increase the max motor power setting in the Soliton
-increase the max. motor voltage a bit
-increase max motorspeed to 5500

Maybe I can increase the slew rate, too. But I can't increase the motor current, due to the clutch. (the current isn't part of the calculation, anyway)


@Batterytoad
How did you calculate the torque? M=P/(2*pi*n)?


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## Batterypoweredtoad (Feb 5, 2008)

@Marc: I used a kw to horsepower conversion for your kw at 5252 rpm, then knowing that hp=torque at 5252 rpm I was able to know torque. Torque is proportional to amps so the fact that you held the amps at 900 throughout the run means you maintained roughly the same torque throughout. All of this is power into the motor of course. Power out would require more info.


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## Lipo Louis (Oct 29, 2012)

4.1 sec from 0-100kmh is extremely fast !! I hope it will be possible. Would second gear be faster? But maybe it will slip when shift from second to third gear...


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## marc02228 (Jan 15, 2011)

Batterypoweredtoad said:


> @Marc: I used a kw to horsepower conversion for your kw at 5252 rpm, then knowing that hp=torque at 5252 rpm I was able to know torque. Torque is proportional to amps so the fact that you held the amps at 900 throughout the run means you maintained roughly the same torque throughout. All of this is power into the motor of course. Power out would require more info.


Ah, you're a smart man Now I remember... when I did my apprenticeship we used the factor 9549 in school as the relation between torque [Nm] and power [kw] 

@Louis
in 2nd gear the acceleration is even harder, but it's not faster because you you have to shift from 2nd to 3rd and you loose too much time while shifting. Additionally the wheels spin in 2nd. 900 A (i think 1000 A would work, too) in 3rd is pretty much the edge of traction.

Lets say, the motor produces 370 Nm of torque.
Gear ratio in 3rd: 1.33
Diff: 4.3
So there would be 2116 Nm at the wheels in 3rd..
Ratio in 2nd is 1.89, so that would almost be 3000 Nm


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## dtbaker (Jan 5, 2008)

marc02228 said:


> in 2nd gear the acceleration is even harder, but it's not faster because you you have to shift from 2nd to 3rd and you loose too much time while shifting. Additionally the wheels spin in 2nd. 900 A (i think 1000 A would work, too) in 3rd is pretty much the edge of traction.



I will second this experience.... hard acceleration starting in 2nd generates wheel spin and hop unless you are careful w/ throttle even in my Miata which has Warp9, 156v, zilla1k. I am running slightly oversize (205) tires, and am still limited by traction. overall times I think are a little better starting in 3rd, but I have yet to verify that emprically with actual timed runs/videos.

I'd suspect that times could be lowered a little with wider stickier rear tires. I would not want to go any wider in the front though as the low-speed turning is pretty stiff even with the 205s.


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## marc02228 (Jan 15, 2011)

Today I had the chance of driving a Tesla Roadster, again... after 4 years time.

I was a bit disappointed of it's acceleration. Does anyone know, if it's power is reduced above 30 °C ambient temperature or so? It felt comparable to the Miata, maybe a bit slower.

Another thing, that I noticed, was that it was much more quiet than the Miata. Especially, when you drive it very slowly, the Miata produces more noise. I think this is due to the bad and overloaded transmission and diff? And the Roadster is just engineered in much more detail.

Does anyone else have an explanation for the noise difference?


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