Tesla Powered Cobra Race Car

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EPowerRacing   10 µW

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Tesla Powered Cobra Race Car

Post by EPowerRacing » Jan 16 2017 8:40pm

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Thought you might be interested in the Tesla Powered Cobra Race Car that we are building and hope to have on track this summer. I have also cross-posted on the DIY forum.

Here's a link to a Youtube Video with further images.
https://www.youtube.com/watch?v=Ci8kHAb6iVw

The motor is from a Model S P85 which is rated at 310 kW peak. However, we have no illusions that we will be able to run the motor at anything close to that for sustained periods due to overheating of the motor/inverter. We are putting in lots of extra cooling but only testing will tell if that helps. All reports we hear of from Tesla Track Days show Model S's going into power limiting within a couple of laps. For longer events, we will probably limit the maximu power to the motor to prevent heat build-up. Although we will have regen capabilities, we will most likely not use it the same reason. (Regen would also upset the brake balance as well which would be undesirable for a race car).

We realized very early on that the massive available torque and an open differential without the benefit of Tesla's traction control system was not a good combination. We worked closely with Jack Rickard/EVTV and Quaife Engineering to produce a custom torque biasing differential. These are now available from EVTV.

We chose the Kia Soul EV as the battery pack donor largely based on DOE test reports which showed it as one of the few OEM packs capable of putting out over 300kW for sustained length of time. It is also one of the lightest packs available. The 30 kw-hr pack (27 usable) only weighs 400 pounds. We purchase what was probably the first Kia Soul EV that was written off, and hauled it across North America! It was fully functional vehicle which allowed us to do some reverse engineering of the CAN bus. We are able to utilize the factory charger for both regular and ChaDeMo charging and obtain cell temperature and voltage data from the BMS. We will be limited in the duration of our runs due to the pack size, but we didn't want to double up on the pack before we even had any real world test data.

The chassis was designed in Solidworks including FEA optimization. The chassis with roll cage weigh about 220 pounds. VR3 engineering took our CAD files and CNC cut and bent all the tubes.

The suspension utilizes C5 Corvette spindles and hubs to keep costs down. However, since we were designing both the frame and A-arms, we were able to dial in exactly the geometry we needed using our SusProg3D suspension analysis program.

Total design weight of the vehicle with driver is 1800 pounds which, even with a torque limited motor, should give us a very good power to weight ratio!

The goal is to have the vehicle on the dyno early spring, then on track for testing in the summer.

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liveforphysics   100 GW

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Re: Tesla Powered Cobra Race Car

Post by liveforphysics » Jan 17 2017 1:24am

Cool project! Cobras rock! If you connect it to an adequate radiator and high flow water pump, I don't see why you couldn't hotrod a lightweight car without over heating issues.
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Rube   100 W

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Re: Tesla Powered Cobra Race Car

Post by Rube » Jan 17 2017 5:21pm

Great project, keep us updated with progress. Keen to understand how you approach the cooling and power management issues. The reverse engineering of the Kia pack sounds like an interesting project in itself.

Punx0r   100 GW

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Re: Tesla Powered Cobra Race Car

Post by Punx0r » Jan 17 2017 6:14pm

Cool project and an interesting nugget of information regarding the high discharge capability of the SoulEV pack.

EPowerRacing   10 µW

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Re: Tesla Powered Cobra Race Car

Post by EPowerRacing » Jan 17 2017 7:25pm

Re-using the Kia Charger was quite easy. A number of interlock conditions must be met for the charger to operate. The hardware ones were easy as Kia publishes the wiring diagrams. However, some information comes via the CAN bus such as drive state (must be in Park), parking brake, door status etc. We used the EVTV/Collin Kidders Savvy CAN program to record CAN traffic under normal (vehicle charging) conditions, found out which ones were relevant, then replay those messages to the charger when we want to operate outside of the vehicle. The BMS system is active at all times and provides cell voltages and temperatures as well as other information.

Rube   100 W

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Re: Tesla Powered Cobra Race Car

Post by Rube » Jan 18 2017 4:50am

Wow, opened up a fascinating rabbit hole of information about CAN data collection. The benefit of a functioning donor vehicle can't be understated! Great job :D
EPowerRacing wrote:....information comes via the CAN....used the EVTV/Collin Kidders Savvy CAN program to record CAN.... replay those messages to the charger when we want to operate outside of the vehicle.....
This approach will benefit harvesting components from donor vehicles as EV tech develops :twisted: Or maybe I'm late to the party :shock:

galderdi   1 kW

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Re: Tesla Powered Cobra Race Car

Post by galderdi » Jan 19 2017 8:13pm

Very cool. What was the driver for the roll cage design? Was it to comply with some rule?

Hillhater   100 GW

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Re: Tesla Powered Cobra Race Car

Post by Hillhater » Jan 19 2017 8:20pm

Great project and very cool car to base it on .
..but what is with the very un-Cobra like roll cage ?...totally out of character and unlike anything i have seen on a track legal Cobra ?
What race series do you plan on entering ?
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liveforphysics   100 GW

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Re: Tesla Powered Cobra Race Car

Post by liveforphysics » Jan 19 2017 9:53pm

That's a cage for folks into survival with car tumbling and rolling. The stock Cobra roll bar is for little more than aesthetics.
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Re: Tesla Powered Cobra Race Car

Post by Dauntless » Jan 19 2017 11:16pm

Looks ready to run for the USAC Silver Crown with that rollcage. Dirt ovals.
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kiwiev   10 kW

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Re: Tesla Powered Cobra Race Car

Post by kiwiev » Feb 10 2017 2:49am

Nice project guys any updates?..
Cheers Kiwi

EPowerRacing   10 µW

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Re: Tesla Powered Cobra Race Car

Post by EPowerRacing » Jul 21 2017 2:09pm

Our Tesla Cobra EV finally hit the race track in June and we have now run 3 races and a number of test sessions with it.

The performance has met our expectations and has surprised a lot of people!

As predicted, range, length of time to recharge, and battery/motor temperatures have been the issues. However, we did complete one 20 minute race at 180kW peak power setting and a second at 220kW. We have run the motor up to 300kW on the dyno, but it is unlikely we will ever be able to run at that level in a race. Qualifying sessions and time trials are a different story though!

Here's a link to some in-car footage:
https://www.youtube.com/watch?v=onPaceYswN4

Regenerative braking can help our range issues, but doesn't help with the temperature issues. We have tried running with various levels of regenerative braking but it makes the car hard to control at turn-in. In the one race we ran with regen on, I compensated by putting on some throttle at turn-in to disengage the regen braking.
(Tesla uses a throttle off/regen on strategy). In the future, we will try to implement a strategy to only use regen during straight line braking.
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liveforphysics   100 GW

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Re: Tesla Powered Cobra Race Car

Post by liveforphysics » Jul 21 2017 3:32pm

Bad ass race!!! Congrats on an awesome project!!
Each carcinogen vapor exposure includes a dice roll for cancer.

Each mutagen vapor exposure includes a dice roll for reproductive genetic defects in your children.

Each engine start sprays them into a shared atmosphere which includes beings not offered an opportunity to consent accepting these cancer experiences and defective genetics life experiences.

Every post is a free gift to the collective of minds composing the living bleeding edge of LEV development on our spaceship.

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kiwiev   10 kW

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Re: Tesla Powered Cobra Race Car

Post by kiwiev » Jul 21 2017 5:11pm

great work guys and a great race.

May have to invest in a dry ice box .


Cheers Kiwi

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