Oil cooled and not a refrigerant in sight: inside the Porsche GT4 e-Performance

Believe it or not, there is a link between the Porsche GT4 e-Performance cover star of SightGlass edition 32 and the Hyundai Ioniq 5 N that graced edition 31 – less obvious that both are performance cars which likely borrowed heavily from technology developed by Croatian electric hypercar manufacturer Rimac in which both companies have a stake.

The mastermind of the Porsche on this page, Björn Förster, a race engineer for the fabled German car-maker, makes no secret about his admiration for the hot Hyundai. He didn’t say so, but you could safely put money on him having one on order – if not in his garage already.

However, apart from the fact no roads authority would issue rego plates for Porsche’s little electric racer and you can drive an Ioniq 5 N away from your nearest Hyundai showroom, the key difference is thermal management.

As we covered last edition, the Ioniq 5 N amps up the donor car’s sophisticated refrigerant- and glycol-based system while applying special temperature control modes for endurance on the circuit, optimal drag strip performance or just going as fast as possible.

By contrast, Förster says the GT4 e-Performance has no air-conditioning or even fans involved in its thermal management setup. Instead of glycol it uses a special oil formulated in conjunction with Mobil 1.

We don’t have any air-conditioning in the car … We don’t even have a fan.

Björn Förster

Förster and team borrowed battery modules from a Taycan road car, located them under the bonnet, in the passenger footwell and behind the seats, then turned up the wick from the Taycan’s 800 volts to more than 900.

Recharging from five to 80 per cent takes just 15 minutes using a 350kW DC charging unit and the battery can accept a staggering 800kW under regenerative braking – the same as the motors can discharge to the wheels.

In fact, massive energy recuperation capability is likely to mean all top-performing electric cars have all-wheel drive – the more axles to harvest from the better.

Amazingly, Förster said the additional regenerative braking capacity of all-wheel drive saved around 250kg in batteries for the same driving range.

A track layout like Sepang in Malaysia – equatorial heat and humidity notwithstanding – has two long straights separated by a hairpin.

Here, the GT4 e-Performance would discharge 800kW then recharge at the same rate on hard deceleration into before deploying full power again.

Sounds like a thermal management nightmare, one Förster claims to have overcome with three kilometres of narrow plastic tube hand-crafted into a cooling coil through which 30 litres of oil are slowly cycled.

“It works, and it’s about 10 times the price of an aluminium system, but 20 per cent more efficient, and half the weight,” the project manager says.

“We don’t have any air-conditioning in the car,” he explained. “We’re only cooling the system with ambient air, we don’t even have a fan.”

When (or if) we see this in production cars remains to be seen but Förster estimated the system is “five years” ahead of the current state-of-the-art for road-going models.

Given a new-generation, all-electric Boxster and Cayman range is due within 18 months, by the end of this decade we could see Spyder and GT4 versions packing something similar what Förster’s skunkworks developed.

Förster believes the oil-based cooling system is the “next big step, a game changer”, to solve the problem of thermal degradation in electric vehicles and enable maximum performance all the way from 100 per cent battery charge to zero. 

“There’s no other option in my opinion,” he emphasises.

“We will see oil-cooled systems in production cars, but I’m not allowed to tell you what it is, and when.”

Compared with glycol-based systems, the non-conductive and super low-viscosity oil – even lower than water – directly flows around the battery cells and through the motors (including their hollow shafts), the gearboxes and the inverter.

Förster said the special oil would work in a Taycan without much modification.

But, as its thermal transfer advantage comes from the ability to directly cool components rather than the glycol-based method where there has to be a barrier between the liquid and electrical components, performance would be reduced because water cooling remains the best method in systems designed for glycol.

Conversely, the GT4 ePerformance’s fully enclosed coolant loop would blow up if any water-based substance was used.

The GT4 e-Performance drivetrain has been optimised to work at 45ºC, which the system is designed to maintain regardless of ambient temperatures.

If the battery and drivetrain can be kept at 45ºC, Förster reckons the GT4 e-Performance can be less expensive to run than an equivalent petrol race car, which needs an engine rebuild after every 75 hours of racing at a cost of €70,000-100,000.

Where all this is headed

Porsche is aiming for carbon neutral supply chain and vehicle production by 2030 – by which time 80 per cent of its total sales must be EVs – and is factoring motorsport into this.

The GT4 e-Performance showcases the tech behind some of this shift but the Mission R concept with which it shares a drivetrain also previews the look of the donor 718’s all-electric successor.

Porsche has also dropped a heavy hint that its next flagship hypercar, following up the 959, Carrera GT and the 918 Spyder, will borrow R&D from the GT4 e-Performance.

The Mission X concept is a glimpse of Porsche’s next range-topper, which has several ambitious tech targets to reach before entering production, including to offer “significantly improved charging performance with its 900-volt system architecture and charge roughly twice as quickly as Porsche’s current frontrunner, the Taycan Turbo S”.

Fast facts about the Porsche GT4 e-Performance:

Variable outputs: The dual electric motors can produce a maximum of more than 735kW and racing simulations show a steady 450kW is available for up to 30 minutes, enough for a sprint race in the Porsche Cup one-make series.

Acceleration: The GT4 e-Performance can sprint from 0-200km/h in 5.6 seconds and maxes out at 285km/h.

Direct cooling system: Built into the motors and battery pack, it ensures power output remains constant for the duration of a race. 

Bodywork: Designed for optimum aerodynamics and thermodynamics, natural fibre composite materials are used to reduce emissions compared to synthetic materials production.

Tyres: Unlikely ingredients for the 18-inch Michelins include orange and lemon peel, pine resin and sunflower oil. Recycled materials include natural rubber and soot recovered from used tyres, as well as metallic waste.

Familiar looks can deceive: Despite its resemblance to the 718 Cayman GT4 Clubsport that donated its chassis, the racing prototype is 14cm wider and uses about 6000 unique parts designed from scratch for the GT4 e-Performance.

Statement of intent: Porsche is going to make a car like this that people can buy. “The GT4 e-Performance world tour is valuable homework so we can develop and build an electric customer racing car for the future,” said the prototype’s project manager Björn Förster.

World tour you say? After its debut in Britain at the 2022 Goodwood Festival of Speed, the GT4 e-Performance travelled to the Pebble Beach Concours d’Elegance followed by the Rennsport Reunion at Laguna Seca where it set a lap time within a five milliseconds of a 911 GT3 Cup car. It then made an appearance at the Hockenheinring in Germany for Porsche’s 75th anniversary before travelling to Asia, then Sydney before going on public display at the Formula 1 Grand Prix in Melbourne.

Last word: “It’s one thing to develop a prototype, but to have it run all over the world in different conditions – such as in circuit racing, hill climbing and even on ice, and ensure the correct recharging infrastructure – takes a substantial effort to realise,” said Förster. “But this work is necessary to create a future racing format that will give our customers the same success and fun they enjoy with our current one-make racing series that uses combustion engines.”