Volvo’s engi­neers rein­vent the wheel

NT News - Motoring - - CARS GUIDE - By STU­ART MARTIN

A NEW spin — if you’ll par­don the pun — has been put on fuel-sav­ing en­ergy re­cov­ery sys­tems by Volvo.

Sim­i­lar in prin­ci­ple to the ki­netic en­ergy re­cov­ery sys­tem (KERS) used in For­mula 1, the Volvo set-up uses a fly­wheel in­stead of a bat­tery to briefly store ki­netic en­ergy be­fore re­de­ploy­ing it to the rear wheels, leav­ing the front wheels to be con­ven­tion­ally pow­ered.

The Chi­nese-owned Swedish mar­que re­cently com­pleted test­ing of the ki­netic fly­wheel on pub­lic roads, and its re­sults sug­gest the sys­tem will be fi­nan­cially vi­able pro­vide and an ‘‘eco­ef­fi­cient so­lu­tion’’.

Volvo pow­er­train en­gi­neer­ing vice-pres­i­dent Derek Crabb says the sys­tem gives an ex­tra 80 horse­power and makes a car with a four-cylin­der engine ac­cel­er­ate like one with a six­cylin­der unit.

‘‘The re­sults show that this tech­nol­ogy com­bined with a four-cylin­der turbo engine has the po­ten­tial to re­duce fuel con­sump­tion by up to 25 per cent com­pared with a six-cylin­der turbo engine at a com­pa­ra­ble per­for­mance level,’’ he says.

The ex­per­i­men­tal fly­wheel KERS works within a vac­uum and is fit­ted to the rear axle and — us­ing brak­ing en­ergy — spins at up to 60,000rpm un­der brak­ing; when the car ac­cel­er­ates, the fly­wheel’s ro­ta­tion (and quick torque build-up) is trans­ferred to the rear wheels via a sys­tem-spe­cific trans­mis­sion.

The front-drive com­bus­tion driv­e­train shuts down as soon as brakes are ap­plied, leav­ing the fly­wheel’s en­ergy to ac­cel­er­ate or pro­pel the ve­hi­cle once it s cruis­ing again.

The sys­tem ap­pears to be sim­i­lar to a petrol-elec­tric hy­brid in the way that it can run with the in­ter­nal com­bus­tion engine yet doesn’t re­quire a heavy bat­tery to store the en­ergy or an elec­tric mo­tor to re-de­ploy it.

Porsche has also en­gaged in ki­netic fly­wheel de­vel­op­ment as part of its hy­brid drive-train pro­grams, and Mazda re­cently in­tro­duced the i-Eloop sys­tem that uses a ca­pac­i­tor (lighter and more ef­fi­cient than con­ven­tional bat­tery sys­tems) to store en­ergy to run an­cil­lary sys­tems in the Mazda6.

‘‘Our cal­cu­la­tions in­di­cate that it will be pos­si­ble to turn off the com­bus­tion engine about half the time when driv­ing ac­cord­ing to the of­fi­cial New Euro­pean Driv­ing Cy­cle,’’ he says.

The fly­wheel tech­nol­ogy test car, an S60, ac­cel­er­ates from 0 to 100km/h in 5.5 sec­onds — quicker than even the most pow­er­ful tur­bocharged six-cylin­der Volvo model.

Volvo says it has been de- velop­ing fly­wheel sys­tems as far back as the 1980s on the Volvo 260 sedan but that fly­wheels made of steel were large and too heavy, whereas the new ex­per­i­men­tal sys­tem is made of 200mm in di­am­e­ter, is made from car­bon fi­bre and weighs about 6kg.

‘‘We are the first manu- fac­turer that has ap­plied fly­wheel tech­nol­ogy to the rear axle of a car fit­ted with a com­bus­tion engine driv­ing the front wheels.

‘‘The next step af­ter com­plet­ing th­ese suc­cess­ful tests is to eval­u­ate how the tech­nol­ogy can be im­ple­mented in our up­com­ing car mod­els,’’ he says.

Volvo pow­er­train en­gi­neer­ing vice-pres­i­dent Derek Crabb demon­strates the car maker’s new ki­netic en­ergy sys­tem

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