Bavar­ian dy­nam­ics to the power of three

FU­TURE MOD­ELS/ BMW has re­leased in­for­ma­tion on dy­namic changes for the next-gen­er­a­tion 3 Se­ries

Business Day - Motor News - - PRE-OWNED NEWS - Mo­tor News Re­porter

BMW is do­ing fi­nal de­vel­op­ment work on the next-gen­er­a­tion 3 Se­ries ahead of its full re­veal. The lat­est testing has been in the area of a key BMW char­ac­ter­is­tic, driv­ing dy­nam­ics and the com­pany has been putting the new 3 through its paces at the Nür­bur­gring Nord­schleife.

Test runs at the leg­endary circuit, known as the “Green Hell”, tra­di­tion­ally serve as a bap­tism of fire for the drive and sus­pen­sion tech­nol­ogy of newly de­vel­oped mod­els.

The com­pany says an ex­ten­sive testing pro­gramme was de­vel­oped for the cam­ou­flaged pro­to­types of the new 3 Se­ries which will ben­e­fit from sub­stan­tial changes to wheel sus­pen­sion, steer­ing, damp­ing, sus­pen­sion and brakes.

The cen­tre of grav­ity is said to be 10mm lower than in the out­go­ing model, axle load dis­tri­bu­tion is bal­anced at 50:50. BMW says the to­tal weight ad­justed for equip­ment is as much as 55kg lighter.

The rigid­ity lev­els of the body struc­ture and sus­pen­sion at­tach­ment — so cru­cial to the steer­ing setup and ride acous­tics — have been en­hanced the com­pany says.

Its agility and steer­ing pre­ci­sion ben­e­fit from ex­panded track widths, while the wheel cam­ber lev­els have in­creased.

In terms of the en­gine port­fo­lio, one fea­ture will be a thor­oughly re­vised four-cylin­der petrol en­gine, the most pow­er­ful four-cylin­der en­gine to be fit­ted in a BMW se­ries pro­duc­tion model.

Yet its fuel con­sump­tion fig­ures are claimed to be 5% be­low those of the pre­de­ces­sor en­gine, partly be­cause de­vel­op­ments have been made to the eight-speed Step­tronic gear­box.

DAMP­ING SYS­TEM

Not only is the body lighter and more rigid in de­sign than that of the out­go­ing model, the same is true of the front and rear axles.

A key fea­ture in terms of sus­pen­sion de­vel­op­ment is a new damp­ing sys­tem. The first liftre­lated dampers to be fit­ted in a BMW model func­tion con­tin­u­ously and pro­gres­sively in re­la­tion to the re­spec­tive spring travel. As such, the vi­bra­tions that oc­cur when com­pen­sat­ing for bumps on the road and dur­ing dy­namic cor­ner­ing can be neu­tralised gently and pre­cisely, says BMW, and pro­vide a bal­ance be­tween sporty flair and com­fort.

“We’re us­ing the liftre­lated dampers as an ac­tive setup el­e­ment so as to cre­ate supreme driv­ing prop­er­ties in all con­di­tions,” says Peter Lan­gen, head of driv­ing dy­nam­ics at BMW. “With short spring travel, a sen­si­tive damp­ing re­sponse en­sures com­fort­able vi­bra­tion com­pen­sa­tion. When the car passes over large bumps, the body move­ments are con­trolled by in­creased damp­ing forces.”

In a spe­cific setup, the lift-re­lated dampers form part of the M sports sus­pen­sion, which in­cludes low­er­ing by a fur­ther 10mm, as well as 18-inch light al­loy wheels and mixed tyres. The M sport sus­pen­sion el­e­ments have in­creased damp­ing forces by 20%, says BMW

“This means the dif­fer­ence from the stan­dard sus­pen­sion is more per­cep­ti­ble than be­fore,” says Lan­gen. “We’ve also made the M sports sus­pen­sion sportier, with more rigid bear­ings and sta­bilis­ers, harder springs and ad­di­tional body struts.”

To fur­ther re­in­force the car’s dy­namic na­ture, the new M sports sus­pen­sion is of­fered solely in com­bi­na­tion with the Vari­able Sports Steer­ing. In ad­di­tion to the speed-re­lated steer­ing as­sis­tance Ser­votronic, this also pro­vides a vari­able steer­ing ra­tio.

Vari­able Sports Steer­ing has been spe­cially re­con­fig­ured for the new gen­er­a­tion 3, with BMW promis­ing that it will re­spond with greater pre­ci­sion to slight steer­ing move­ments, with­out seem­ing ner­vous in cen­tral po­si­tion.

Changes to the setup of the steer­ing will be felt on long bends, as well as when chang­ing di­rec­tion sev­eral times in rapid suc­ces­sion, says the com­pany.

Then there is the M sports dif­fer­en­tial in the rear axle which is linked to Dy­namic Sta­bil­ity Con­trol, en­sur­ing need­sori­ented lim­i­ta­tion of ro­ta­tion speed com­pen­sa­tion be­tween the rear wheels on the in­side and on the out­side of a bend. De­pend­ing on the sit­u­a­tion on the road, it is pos­si­ble to pre­emp­tively in­flu­ence both un­der­steer­ing and over­steer­ing with­out brake in­ter­ven­tion.

The ac­tive dif­fer­en­tial lock dis­trib­utes drive torque se­lec­tively be­tween the rear wheels pre­vent­ing slip on a wheel with re­duced sur­face grip, while en­sur­ing en­gine power can be used un­re­strict­edly to gen­er­ate sporty driv­ing plea­sure.

“Un­like con­ven­tional me­chan­i­cal locks, the reg­u­lated M sports dif­fer­en­tial can op­ti­mise so much more than just trac­tion,” says Lan­gen. “In ad­di­tion to cor­ner­ing dy­nam­ics, there is a tan­gi­ble in­crease in drive sta­bil­ity in the event of load changes, for ex­am­ple. This al­lows the new 3 Se­ries sedan to be driven re­mark­ably con­fi­dently and ef­fort­lessly even when trav­el­ling in dy­namic style.”

For sporty driv­ing, the ac­tive dif­fer­en­tial lock pro­vides much higher lev­els of trans­verse ac­cel­er­a­tion, as well as a per­cep­ti­ble boost in dy­namic per­for­mance when ac­cel­er­at­ing out of bends. It sup­ports op­ti­mised sta­bil­ity, pre­ci­sion and cor­ner­ing pre­dictabil­ity with­out brake in­ter­ven­tion.

The cam­ou­flage still hides much of the re­vised de­sign but the new 3 will be a lit­tle wider and lower. Above right: Sus­pen­sion up­grades aim to im­prove dy­nam­ics even more in the new gen­er­a­tion.

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