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

CAR (UK) - - News -

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

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