Look! All-wheel drive without the propshaft
Petrol and electric power work in harmony in a system set to take Ford’s hot hatch to another level. By Ian Adcock
THINK HYBRID as in Porsche 919 Hybrid Evo, not hybrid as in Toyota Prius. The merging of electric and internal combustion motors can be focused on economy or performance, or a bit of both. The new hybrid system we’ve tested – and which we expect to be used in 2020’s Ford Focus RS – is very much about performance.
Called eTwinsterX, the tech from GKN has been featured in CAR before (November 2017), but now we’ve tried it for ourselves. Here’s how it works – and why we’re convinced it’s right for the RS.
Small motors, big output 1
The next-generation Focus RS is in line to become a high-performance hybrid combining an electrically-driven rear axle with a conventional, but downsized, petrol engine powering the front wheels. That combination could eclipse the old car’s 345bhp and get closer to the outgoing Mercedes-AMG A45’s 376bhp. A two-speed gearbox attached to the electric motor would mean scintillating acceleration from a standstill as the electric motor’s torque augments the petrol engine, but also up to 10 per cent better economy in highspeed cruising. And cornering would be transformed as the e-motor vectors torque between the rear wheels.
Why it’s right for RS 2
With the new Focus lacking a transmission tunnel, under the flat floor is an ideal location for the batteries, keeping the centre of gravity low for enhanced dynamics. Furthermore, the new Focus is, on average, 50kg lighter than its predecessor, which would go some way to compensating for the extra weight of the batteries and e-motor. Ford and GKN have form, with the previous RS benefitting from a nonelectrified predecessor of eTwinsterX to deliver class-leading dynamics and Ford’s first drift mode. Stricter RDE2 emission regulations in 2020 make this perfect timing for a hybrid option.
Independent but united 3
To create eTwinsterX, GKN combined its non-electric Twinster clutch technology at the front with a 120kW e-motor driving the rear wheels via a unique two-speed transmission.
With a conventional four-wheel-drive system, slip at the front wheels defines how much torque can be delivered to the rear; with the rear e-motor, the torque delivered to each axle is totally independent. This gives greater freedom to apply negative torque for true torque vectoring.
Two rear gears 4
The two-speed system – a low first for launch; second for everything else – allows the e-motor to run in or close to its sweet spot, improving overall efficiency for greater range. Combine that with Twinster and power is delivered from the e-motor to the wheel that has the best grip – another efficiency gain, since energy isn’t wasted using the brakes to slow down tractionless spinning wheels.
Baptism of ire… and ice 5
CAR drove GKN’s Mercedes-AMG GLA45 4Matic demonstrator at the Arjeplog winter testing ground, with a petrol engine up front and e-motor behind, offering a choice of front-, rear- or all-wheel drive in Comfort, Sport or Automatic modes; an energy recuperation mode is under development.
Compared to traditional all-wheeldrive systems, eTwinsterX feels more subtle in its intervention. During cornering the outer wheels help to pull the car into a much tighter arc, eliminating understeer or any sense that the front will wash away on the treacherously slippery ice. And the system’s myriad torque-vectoring opportunities make for plenty of driftrelated fun should the mood take you.
A petrol engine drives the front wheels; there’s no transmission tunnel, so underloor batteries power the e-motor driving the rear wheelsClever clutches allow ultra-precise torque vectoring, eliminating braking which wastes energy