Which Electric Car recently came across an interesting electric race car project that has come out of Vancouver, Canada. It is a Shelby Cobra replica body powered by a Tesla P85 drivetrain and a battery pack from a Kia Soul EV.
We’ve been talking to one of the builders Doug Yip about it. Doug is a long time road racer (Sunbeam Tiger, Mustang GT1, Toyota MR2) in the PNW and had been wanting to build an electric race car for a while. However, up until now, the cost of doing this has been prohibitive. The availability of OEM EV components in the salvage yard has changed things.
This car is being collectively built by a group of friends who love the idea of doing something different. They have been working on the project since December 2015 and call themselves “EPower Racing”
The motor is from a Tesla Model S P85 which is rated at 310 kW peak. However, they have no illusions that they will be able to run the motor at anything close to that for sustained periods due to overheating of the motor/inverter. The team are putting in lots of extra cooling but only time will tell if that helps.
All reports they hear from Tesla Track Days show Model S’s going into power limiting within a couple of laps. Although the car will have regen capabilities, they will most likely not use it for the same reason. Regen would also upset the brake balance as well which would be undesirable for a race car.
Here is what Doug has to say about the 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.”
“Our Tesla Cobra EV has finally hit the race track in anger 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!”
We would like to congratulate Doug and the team at EPower Racing on their EV race car project and wish the well in future events. Hopefully they will inspire more people to start realising the potential of electric vehicles in grass roots motorsport.
Credit: Doug Yip – EPower Racing