The elec­tric mo­tor that thinks it’s a diœ

It could hap­pen. Mak­ing smarter use of elec­tric mo­tors takes torque vec­tor­ing to the next level. By

CAR (UK) - - Contents - Ian Ad­cock


IGHT NOW it seems like a very long way from the red-blooded per­for­mance of Ford’s Fo­cus RS hot hatch to the quiet ef­fi­ciency of a hy­brid city car. But tech in­no­va­tors GKN say they can help bridge the gap with a new trans­mis­sion that mixes and matches the best of both worlds.

The start­ing point is Twin­ster, GKN’s ac­claimed torque vec­tor­ing sys­tem. It’s a term that’s of­ten slop­pily em­ployed, but GKN are very clear about what they mean by torque vec­tor­ing: a sys­tem to send pre­cise amounts of torque to in­di­vid­ual wheels. Us­ing two clutches, Twin­ster al­lo­cates torque be­tween front and rear axles and be­tween the rear wheels. The big ben­e­fit on a car such as the RS comes dur­ing cor­ner­ing when an out­side wheel will be sped up (rather than an in­side wheel be­ing braked, the less en­ergy-ef­fi­cient so­lu­tion em­ployed else­where).

The new break­through, un­veiled at the Frank­furt show and avail­able in the early 2020s, is clum­sily called eTwin­sterX. It’s a com­pact elec­tric axle that can be used on front-drive, rear-drive or all-wheel-drive cars, on road or off, hy­brid or fully elec­tric.

A typ­i­cal cur­rent hy­brid has a com­bus­tion en­gine on one axle and an elec­tric mo­tor on the other. There is usu­ally a dis­con­nect sys­tem that switches from elec­tric run­ning to com­bus­tion-en­gine run­ning. The sin­gle gear ra­tio be­tween the e-mo­tor and wheels is set up to de­liver good launch per­for­mance, but as the car’s ve­loc­ity in­creases the e-mo­tor runs out of speed and the com­bus­tion en­gine takes over the job.

GKN’s new sys­tem works dif­fer­ently. It has two gears, which al­lows the elec­tric mo­tor to stay en­gaged at all road speeds, thus re­quir­ing less help from the com­bus­tion en­gine. The re­sult is good range, good per­for­mance and less pol­lu­tion.

A lower first gear delivers a good launch and low-end per­for­mance in pure elec­tric mode and the sec­ond, longer ra­tio helps with higher speeds.

GKN’s Theo Gass­man says: ‘The two-speed sys­tem al­lows you to run the e-ma­chine in or close to its sweet spot, im­prov­ing over­all ef­fi­ciency for greater range. Com­bine that with Twin­ster and you can de­liver power from the e-ma­chine to the wheel that has the best grip for an­other ef­fi­ciency gain as you’re not wast­ing en­ergy by us­ing the brakes to slow that wheel down un­til it re­gains trac­tion.’

3 TORQUE VEC­TOR­ING Torque is di­verted via Twin­ster elec­tric axle to wheel or wheels where it’ll be most use­ful. 1 ELEC­TRIC MO­TOR E-mo­tor is used more e iciently: com­pact two-gear sys­tem al­lows elec­tric mo­tor to stay in use at higher road speeds. 2...

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