Com­modore-type power for new As­tra

Motor Equipment News - - OEM - By John Ox­ley READER RE­PLY 01506018

High per­for­mance has long been a key­note for the Holden brand, and even though its big rear-drive Com­modore mod­els are due to be axed when the com­pany ceases pro­duc­tion in two years, the per­for­mance credo will con­tinue.

Lat­est in a long line of Holden per­for­mance mod­els is the new­lyre­leased Holden As­tra VXR, a beau­ti­ful four-seat coupe based on the Ger­man­built Opel As­tra OPC that man­ages to mix prac­ti­cal­ity with out-and-out fun!

As al­ways, the heart of any car is its en­gine, and the one that beats in the As­tra VXR is noth­ing less than a 206kW two-litre tur­bocharged di­rect in­jec­tion which achieves max­i­mum torque of 400Nm and can sprint from zero to 100km/h in six sec­onds and on to a top speed of 250 km/h. To put this into per­spec­tive, that’s only 2kW less power and 50Nm MORE torque than found in the 3.6-litre V6-pow­ered Com­modore SV6, and only 52kW less than the mighty six-litre Com­modore SSV V8!

The VXR’s four-cylin­der en­gine of­fers 25 per­cent more max­i­mum torque than the pre­vi­ous Opel As­tra OPC and also boasts 30kW more power. This trans­lates into 104kW/litres (140 bhp/ litre), the high­est spe­cific out­put per litre in any Holden pro­duc­tion car.

Although based on the pre­vi­ous en­gine, the lat­est ver­sion has much bet­ter fuel econ­omy, re­duced by 12 per­cent, while CO2-emis­sions have been re­duced by 14 per­cent. The CO2-emis­sions of the As­tra VXR have been low­ered to 189 g/km and fuel con­sump­tion to 8.1L/100km.

There’s a com­pletely new state-ofthe-art en­gine air in­take sys­tem to feed as much air to the tur­bocharger as pos­si­ble. In ad­di­tion, the ex­haust sys­tem was op­ti­mised to fur­ther im­prove the flow of the ex­haust gases and im­prove the en­gine per­for­mance. The tur­bocharger it­self was fur­ther en­hanced to with­stand even more charge air pres­sure and was in­creased by us­ing new com­po­nents.The en­gine’s high ther­mal en­durance is fur­ther sup­ported by a wa­ter jacket which extends to the bot­tom of the cylin­ders, and oil-spray cool­ing of the un­der­side of the pis­tons.

Both camshafts re­spond au­to­mat­i­cally via an elec­tro-hy­draulic cam phaser to match valve open­ing times to the en­gine load sta­tus via the en­gine con­trol unit. In ad­di­tion, a higher over­lap at lower speeds with con­tin­u­ously vari­able camshaft phas­ing en­sures the tur­bocharger re­sponds more quickly.

The out­let valves are sodium-filled and all valves are ac­tu­ated via low fric­tion roller valve levers.

Other en­gine fea­tures are two counter-ro­tat­ing bal­ance shafts, low-main­te­nance chain drive for the camshafts and a cast-on oil fil­ter hous­ing, which is eas­ily ac­ces­si­ble from above.

An oil change sim­ply re­quires re­plac­ing the car­tridge and is sig­nalled by an in­ter­val in­di­ca­tor. Sen­sors mea­sure wear and tear of the fully syn­thetic lu­bri­cant ac­cord­ing to pa­ram­e­ters such as the num­ber of cold starts and the num­ber of ig­ni­tion.

Opel de­signed a high per­for­mance chas­sis pack­age geared es­pe­cially to­wards lat­eral dy­nam­ics and su­perb han­dling qual­i­ties for the As­tra VXR, to com­ple­ment its pow­er­ful en­gine.

The chas­sis benefits from sev­eral de­ci­sive el­e­ments that all en­hance the car’s driv­ing dy­nam­ics:

High per­for­mance struts (HiPerStruts) on the front wheel sus­pen­sion, the mecha­tronic FlexRide chas­sis sys­tem, a me­chan­i­cal multi-plate slip dif­fer­en­tial and Brembo brakes.

The FlexRide chas­sis sys­tem lets the driver sharpen the char­ac­ter­is­tic shock ab­sorber line, the steer­ing and the gas pedal re­spon­sive­ness. He can choose be­tween three dif­fer­ent modes, with each mode of­fer­ing a unique and spe­cific ex­pe­ri­ence of high per­for­mance driv­ing. The Stan­dard mode de­liv­ers all-round per­for­mance while com­fort is pre­served at all times for ev­ery­day drive sit­u­a­tions.

At the touch of a but­ton the Sport mode stiff­ens the chas­sis sus­pen­sion, in­creases agility by re­duc­ing body roll, and makes the steer­ing more di­rect. Mean­while, the VXR mode cre­ates the ul­ti­mate driv­ing ex­pe­ri­ence: steer­ing be­comes even more di­rect in com­par­i­son to the Sport mode, the throt­tle is more re­spon­sive and the chas­sis set­ting is geared to­wards de­liv­er­ing max­i­mum per­for­mance.

In ad­di­tion, a Watt’s link which has been tried and tested in mo­tor sports has been fit­ted to the rear axle of the As­tra VXR and is com­bined with a com­pound-crank axle, en­sur­ing su­perb lat­eral sta­bil­ity and steer­ing pre­ci­sion, es­pe­cially in bends.

The link­age com­prises a short, piv­ot­ing cen­tre link with a ball joint at each end to which the lat­eral links from the wheels are bolted. The sys­tem en­sures that around 80 per­cent of all lat­eral loads are ab­sorbed by the rear sus­pen­sion.

The 19-inch al­loy wheels that come as stan­dard add a fur­ther sporty note to the car. In ad­di­tion, the en­gi­neers fine­tuned the chas­sis to VXR stan­dards by mod­i­fy­ing the dampers and stiff­en­ing the springs and bush­ings.

In ad­di­tion, the As­tra VXR has been fit­ted with a me­chan­i­cal multi-plate limited slip dif­fer­en­tial on the front axle which brings max­i­mum torque to the road. The dif­fer­en­tial, which con­tains sev­eral clutch plates, helps to re­duce wheel slip when there are very high lat­eral forces un­der ac­cel­er­a­tion, for ex­am­ple, or changes in the tex­ture of the road sur­face. It is also ideal for ex­cur­sions onto the race track.

The co­or­di­na­tion of the dif­fer­en­tial with a static ba­sic lock­ing torque guar­an­tees a har­mo­nious re­sponse and tran­si­tion be­hav­iour be­tween load and over­run, elim­i­nates in­flu­ences on the steer­ing and self-steer­ing be­hav­iour dur­ing over­run, and en­sures trac­tion re­serves in the case of highly var­ied wheel loads.

The ESP sta­bil­ity con­trol in the As­tra VXR of­fers three dif­fer­ent modes which al­low the driver to de­ter­mine how chal­leng­ing and sporty he wants to drive.

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