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Discussion Starter · #1 · (Edited)
Hi All,

New here - I've been reading for some time and there is some great information on these forums. So thanks for that.

I didn't want to make a posting here until we had our machine further along to avoid controversy and typical internet banter. But I think it is now time to share what we are doing, and I hope you all like it!

I come from a motorsport background and have previously built, developed and raced sports cars in various series in Canada and the US. In my world, electric cars are looked at as being silly and not practical for real performance driving. Obviously things are changing very quickly, and it is quite possible that by the time our car is done there will already be some very capable electric sports cars.

However regardless of that - my goal with this build is to put together a very capable electric sports car to learn about electric drive and control systems, as well as to inspire and motivate people in my world to how amazing electric vehicles can be. Those of you that have electric vehicles know the many advantages that might not be obvious to most.

The Lotus Evora was chosen because it is really one of the most under-rated sports cars out there. Extremely rare, fantastic chassis, and a less than inspiring engine. Mid engine, which is favourable to the Tesla DU, simple single CAN bus system which makes the reverse engineering job easier, fibreglass body that comes off the frame which makes fabrication a lot easier, and a 2+2 chassis design that actually only has two seats (the car is available both in 2 seat and 4 seat variants). The extra length allows for great space to mount the batteries for a low polar moment of inertia.

The compromises:

-We are using two Chevy volt batteries simply because we can't justify the cost (yet) to make a custom battery pack.
-Jason (wk057) and Michal (eldis) among others have made me aware of the Tesla DU limitations in terms of continuous power output, so for the initial build our goals will just be for time attack where we can do two laps or so at full power, before we overheat the inverter.

The car will be a fully complete street car - the best thing to compare it to would be a 991 Porsche GT3. The goal is to have a comfortable, exciting and attention gathering car for the road that is still capable of extreme performance on the racetrack.

Design Goals:

-We're hoping for close to 200km of range (125 miles). This will not be "EPA" range but closer to a 50mph average backroad cruise.
-We're looking for around 420hp at the wheels (roughly 350kW at the motor)
-We're aiming for a laptime of 1:16.1 at Cayuga on a Hankook TD soft tire. I know this is meaningless to you all, but it will be fun to circle back to here once we are on the track. For reference the stock Evora on old tires could not best a 1:22 at Cayuga - and believe me I was trying!! The Evora had 250hp at the wheels when we dyno tested it stock.
-We are trying to update the less than desirable aspects of the Evora - mainly the interior to make it more modern.

We are using a Motec controller and M1 build, using their IDE to do most of the control of all of the modules in the car. The M1 will directly control the Volt slave BMS units, control the Chademo contactors and communication, J1772 communication and charging control, offer advanced traction control and different driving modes, and be an advanced data logger. We are still using the OEM Tesla motor controller and have had our friends at Avantics in Switzerland reflash the OEM Tesla module, and supply another module that communicates with the Tesla DU to keep it happy and thinking it is still in an original Tesla.

Here's a video of the drive unit on the dyno with a single Volt battery. We still had the Volt fuses in on this one so we only did a quick power burst to ensure the drive unit was not in limp mode. It wasn't - it sucked 700 amps out of the Volt battery!

https://www.youtube.com/watch?v=d8rYXBYqPX8

I have to say a huge thanks to Vincent (bigmouse) and Michal Elias (eldis) for their incredible help through this journey so far. I started this project with very little CAN knowledge, zero programming knowledge and zero EV / electric car knowledge. So it's been a very very steep learning curve and I couldn't have done it without awesome people like these two. For everyone else that has helped, thank you as well.
 

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Hi
I am really interested in how you are going to make out,

Are you going to use some sort of traction control?

I ask this because I am having difficulty in controlling my car

http://www.diyelectriccar.com/forum...dubious-device-44370p15.html?highlight=duncan

With a powerful IC car (many years ago I used to hill-climb a mini with a 170hp Lancia unit in the front) I remember being able to feel before I lost traction

With my electric drive it seems to just go! - the first thing I know is that my tires are screaming and I am stepping sideways
 

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That is such an great idea, using the Motec to give traction control. Is there an option for stability control?

Your project is fantastic.

Great job.

Me want.

:D
 

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This will be a nice beast when done.
Wouldnt want to know what all this kit will cost once complete :D

Will you be cooling the chevy volt pack via the intergrated cooling loop?
 

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That display is beautifully integrated! I have absolutely zero questions or suggestions, very well thought out design and great use of existing building blocks to keep costs in check!
 

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What a great job and a beautiful platform to work with! It's got a easy to modify, MIG weldable, steel rear sub-frame. It fits the Tesla drive unit ( I assume that's what the DU stands for) like a glove, with better access than in a Tesla with the bottom and top exposed. If someone gives you a bad time about putting the DU in the crush zone (I assume that's what the replaced accordion-like structure is) you could add a faux rubber and foam exhaust diffuser to protect the rear of the car. They seem to be making them almost as big as barn doors these days!

One area that caught my eye is the cut back or removed rear seat/luggage shelf/fuel tank cover box structure. It looks like, if it has indeed been modified, it may provide some important lateral and torsional stiffness to the chassis. If this is a problem, a well designed battery box could probably make up for it, structurally.

Also, I wonder if there might be an excess rear weight bias. With no or a smaller radiator(s) in the front and the main battery located behind the front seats stretching back close to the rear suspension area, this could be a problem. It might be necessary to sacrifice some low center of gravity for a better weight bias by bunching the battery cells closer to the front seats. It would be a shame to have to bolt lead weights to the front bumper like the old 911s had to reduce their tendency to swap ends!
 

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Discussion Starter · #12 ·
Traction control will be done using the Motec engine controller. It will be implemented either with power limit requests sent over CAN to the DU, or through drive pedal input manipulation. This isn't sorted yet but should be pretty neat when it's all worked out.

Hi
I am really interested in how you are going to make out,

Are you going to use some sort of traction control?

I ask this because I am having difficulty in controlling my car

http://www.diyelectriccar.com/forum...dubious-device-44370p15.html?highlight=duncan

With a powerful IC car (many years ago I used to hill-climb a mini with a 170hp Lancia unit in the front) I remember being able to feel before I lost traction

With my electric drive it seems to just go! - the first thing I know is that my tires are screaming and I am stepping sideways
 

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Discussion Starter · #13 ·
Thank you! The OEM Evora's ABS also features stability control. We've retained the OEM yaw/steering sensor and ABS, and have already tested that to be working without the OEM ECU in place. We didn't test it without the factory gauge cluster in place however.. so hopefully that doesn't pose a problem.

There is a sport mode for the stability program that actually allows a decent bit of a yaw before any intervention from the system. It's quite nice!

That is such an great idea, using the Motec to give traction control. Is there an option for stability control?

Your project is fantastic.

Great job.

Me want.

:D
 

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Discussion Starter · #14 ·
Yes, at first we are going to just use water through a radiator for the battery cooling, but the intention is to use one radiator, and splitting the output of that radiator - one output will go through chillers into the batteries, and one output will go directly into the motor which is happier to see a higher water temp.

The batteries and the motor each have their own water pump which is PWM controlled by the ECU.

This will be a nice beast when done.
Wouldnt want to know what all this kit will cost once complete :D

Will you be cooling the chevy volt pack via the intergrated cooling loop?
 

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Discussion Starter · #15 ·
Thank you! Yes the car really is almost the ideal candidate. I put a lot of though into the bases vehicle and when I added everything up the Evora was the clear winner. Maybe I'm biased because I think it's such a beautiful car.

The top of the fuel tank area was sheet aluminum, and there is now a lateral brace that connects the frame to support the upper layer of batteries. So the lateral stiffness should be the same. Since it is just sheet, any torsional stiffness provided would be negligible I would imagine. The under-tray is also aluminum and acts to further lateral stiffness as well (it's fairly thick stuff).

As far as rear bias, I expect the rear weight to be about the same. The motor is further back, but the batteries are much further forward than the factory engine. We weighed the OEM engine and gearbox to be ~870lbs IIRC along with the fuel tank, mufflers, and other ICE components. The Tesla motor and batteries are approx ~1030lbs IIRC, and we removed about 20lbs from the rear frame. So call it 1010 lbs.

We are installing a composite rear hatch without glass, and a carbon diffuser, so that should reduce rear weight by another 50lbs or so, and the OEM battery is no longer there, which is approx another 50lbs. So call it 910.

So the rear weight is fairly comparable to stock, and the front weight will be much increased over stock, as we are adding the charger, electric power steering pump, and HV air conditioning condenser to the front. I expect most of our weight addition to actually be at the front, and I think our weight distribution will be closer to ideal as a matter of fact!

The car did have a little bit too much trail in oversteer for my liking - I wasn't able to attack the corners as hard as I would have liked. So I am hoping the additional front weight should help the bias. I'm used to racing front engine RWD cars which are very much the opposite (stable / understeer in, oversteer on throttle), and so I like a car that can attack the entry. I've attached a photo of my race car just for fun, as well as the Porsche 991 GT3 cup cars that I work with (since you mention 911s!). I lead the setup and technical work with the team up here. We will be racing at Sebring next weekend actually!

What a great job and a beautiful platform to work with! It's got a easy to modify, MIG weldable, steel rear sub-frame. It fits the Tesla drive unit ( I assume that's what the DU stands for) like a glove, with better access than in a Tesla with the bottom and top exposed. If someone gives you a bad time about putting the DU in the crush zone (I assume that's what the replaced accordion-like structure is) you could add a faux rubber and foam exhaust diffuser to protect the rear of the car. They seem to be making them almost as big as barn doors these days!

One area that caught my eye is the cut back or removed rear seat/luggage shelf/fuel tank cover box structure. It looks like, if it has indeed been modified, it may provide some important lateral and torsional stiffness to the chassis. If this is a problem, a well designed battery box could probably make up for it, structurally.

Also, I wonder if there might be an excess rear weight bias. With no or a smaller radiator(s) in the front and the main battery located behind the front seats stretching back close to the rear suspension area, this could be a problem. It might be necessary to sacrifice some low center of gravity for a better weight bias by bunching the battery cells closer to the front seats. It would be a shame to have to bolt lead weights to the front bumper like the old 911s had to reduce their tendency to swap ends!
 

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Discussion Starter · #16 · (Edited)
Sorry for the lack of updates guys - it's been a busy time. We finally crossed a big milestone by getting the car on the dyno with both battery packs. It made a whopping 440 horsepower to the wheels!

I wasn't able to apply full throttle until the end of the dyno run, as the axle torque would exceed the dyno limit. So the dyno graph doesn't look at all like what it should - I will try to do another one today and spin the motor up to a higher RPM to show more of the "flat horsepower" characteristic of electric motors. It looks like the motor won't exceed the dyno torque limit beyond 7500rpm or so, so I will apply a torque limit below that just for the dyno pull. It works out to about 300lb-ft of torque (4000nm dyno axle torque limit with a 9.3 gear reduction, do the math if you're bored).

The thing is nutty. We are using the OEM Lotus pedal and manipulating that to send to the Tesla DU, and the Advantics controller is taking care of the rest for the Tesla DU.

Our Motec C1212 display is looking pretty awesome if I do say so myself, and it will continue to get better as I send it more channels and refine the design.

I've got the regen paddle for the steering wheel all designed and 3d printed, so that will be tested shortly and I'll have it either 3d printed out of aluminum or machined. I'm pretty excited about that part of it! I'll try to make a post with more details about how we're doing that if you're all interested.

I've also got a number of data logs I'd be happy to share with you all. I am currently mapping motor efficiency on the dyno, which is basically wheel power divided by battery power as there is currently no other load on the battery while we are doing our dyno tests.

There will be a YouTube video coming up soon, stay tuned!
 

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Your setup and integration looks awesome. So it sounds like you have made headway with getting the regen to work ?
Cant wait to see it on the road.

Jeff
 

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Congratulations to Sasha for an amazing build!!
I've never seen anyone building a performance EV this quickly. It is a pleasure to be helping him on the Tesla DU control - I wish every customer picked up things as quickly as he does.

Yup, regen is working. We had to tweak a few things, since everything was still being tested.
The Tesla Drive Unit control is done using UMC Drive 3, by emulating pretty much entire Tesla Model S, to make the Drive Unit happy.

Theoretical maximum of this unit is around 420kW, but that presumes almost no sag of the batteries doesn't account for some of the losses. I'm sure that the final vehicle will get near that :)
 
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