Pure electric cars have been around for a few years now at the top level of motorsport. Mercedes abandoned the DTM and Porsche abandoned Le Mans to pursue the Formula E crown, such is their conviction that EVs are the future. World Rally Cross has confirmed the cars will be pure electric by 2020. This hadn’t permeated club motorsport thus far. Until now….
At the last round of formula G, a satin black Zero-EV R32 Skyline navigated the track in complete silence.
The reason for that was that in the boot of this car lies the bleeding edge of propulsion – a 400kW (536hp) pure electric Tesla drive unit from a Model S with the potential for a staggering 1000lbft of torque. When you think these drives will accelerate the 2.2 tonne Model S to 60 in 2.27 seconds, putting it in a much lighter car was always going to prove interesting.
I met the owner Chris Hazell a few weeks prior to the event at the Fully Charged show at Silverstone hosted by Robert Llewellyn (Red Dwarf) and Johnny Smith (5th gear). I was blown away by the fact he had Tesla drive units on the shelf and a 3rd party control system which meant they could be custom mapped (Chris thinks there is easily 700hp in the motor with a custom tune). There was even a beautifully presented bay window camper van with a Tesla motor in the back!
Coincidentally I’d also seen a viral post on Stav-Techs Facebook page of his Skyline demonstrator doing donuts at his industrial unit, so it made sense to invite him to pop his competition cherry at the next round of Formula G.
Here we go again 😄 can’t get enough of this thing!! So much fun no delay on throttle response is instant so controllable. Future of drifting for sure. Fast Car Magazine
Posted by Zero EV on Wednesday, May 30, 2018
Some interesting discussions followed with series organiser Andy Bevan as to the availability of recharging points at the circuit. This is the sort of infrastructure that is urgently needed to support the inevitable move to full electric cars in motorsport. WRX cars making the bold move to full electric in 2020 will be the acid test.
Fortunately, Rockingham just happened to have a 32A outlet in a blue cabinet by the podium. Game on….
Electric motors are relatively simple by comparison to an ICE (Internal Combustion Engine). They boil down to a rotor (bit that turns) and stator (bit that doesn’t). Varying the electric fields in copper windings create magnetic fields between them which in turn creates a force that turns the rotor. Anyone who has played with magnets will appreciate the forces of attraction and repulsion between poles.
Some interesting points about an electric motor such as the Tesla unit Chris uses:
It is an AC (Alternating Current) induction motor. This means that the D.C from the battery has to be converted to A.C. by means of an inverter. Induction means there are no permanent magnets in the motor and the magnetic fields are generated by the inverter controller.
In the picture, the motor is the left half of the cylinder, the 9:1 Reduction gear is in the middle, the inverter is the right side of the cylinder and the diff is located behind it. Chris has taken the entire back axle from a Tesla Model S and fabricated mounts for the back end of the Skyline for simplicity (and the fact that the driveshaft’s are rated for 4 figure torque).
Electric motors feel very different to ICE motors. For one thing, they don’t need to idle, so there is no need for a clutch to disengage transmission and engine.
They make maximum torque at zero rpm, which is why the model S is such an effective drag racer (especially over the eighth mile, see the Tesla Racing Channel making rednecks sad on youtube) . They will spin to a perfectly smooth 19000 rpm, so need a reduction gear to reduce rotational speed to a sensible wheel speed and don’t need a gearbox.
They can run in a regenerative mode, so if the car is coasting down, the motor becomes a generator, and can recharge the battery, extending the range. For drifting and gymkhana, this effect can be strong enough to lock the rear wheels, so rear brakes and a hydro aren’t necessary, just a button that engages 100% regen.
The smaller 300kW tesla drive unit weighs 92kg all up, the larger 400Kw about 130kg, so much less than an ICE, a transmission and all the supporting systems. Second-hand drive units start from about 8k, so already compare favourably with ICE units of a similar output.
Throttle response is instant, lag isn’t a thing. As soon as you think ‘torque please’, you are converting tyres to smoke.
The limiting factor at the moment is the battery technology. Chemistries like Lithium Ion and Lithium Polymer will be dominant for the next decade or so and have made EVs viable. Chris uses the battery from a Chevrolet Volt, which has a capacity of 16Kwh, weighs about 200kg and is worth about £2k second-hand. KWh means Kilowatts (thousands of Watts) per hour.
To put this amount of energy into perspective; An average UK house uses 10kWh per day. This means the battery in Chris’s car could run an entire house for over a day and a half. The most power you can pull from a domestic plug is 13amps x 240volts=approx. 3.2kW. Remember the output of Chris’s motor is 400kW! That is down to a combination of a 400 Volts and a staggering 1000 Amps of current! Not the sort of plug you want to stick your fingers down!
A bit of quick math shows that if the motor was running flat out at its 400kW peak it the battery would only last 2.5 minutes.. In practice the motor isn’t at peak all the time and with regen on it meant Chris could complete about 7 gymkhana runs to a charge, recharging the battery over lunchtime. Chris plans to double the capacity for future events which would free him from relying on a charger for the day. Using more expensive Tesla batteries, Chris can go to 40KWh without adding much weight.
The cars setup improved dramatically over the course of just one day. Monster Energy pro driver Luke Woodham got behind the wheel for a drive and had this to say;
“I found it unbelievable to drive, such great feedback through the throttle pedal, really up my street! I was very unsure about how it would perform, but rest assured it absolutely blew my expectations away!”
Luke was so impressed he asked to use it for the remainder of the Formula G season and beyond, and it may return for the next round sporting a very familiar logo. I hope we see it at some of the big international events; it would certainly provoke some interest.
Battery management aside, the lack of an ICE soundtrack is an oft heard criticism, and one I have sympathy for, but in the age of venues being shut for noise, this may have an upside. Also, the energy used in making the noise is instead converted into forward speed. I think all acceleration junkies and environmentalists would both approve.
So, in a decade’s time, when EVs represent the mainstream in grass roots motorsport, remember you saw it here first in 2018.
Words: Andy Stevens