WHAT MAKES AN M?

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“It was on a road trip from BMW HQ in Mu­nich, Ger­many, across to the French Ca­mar­gue, via Italy, that I drove one of the very first M3 sedans, the E30”, writes John Ox­ley. “Flash for­ward nearly 30 years, and more than 19,000km, and I was the wheel of the lat­est M3, in Taupo, New Zealand.”

Both drive ex­pe­ri­ences were mem­o­rable. In its day, the first 2.3-litre four-cylin­der E30 M3 was a lit­tle rocket ma­chine par ex­cel­lence, of­fer­ing buy­ers the rare ex­pe­ri­ence of driv­ing a car which had been de­signed to give them the ul­ti­mate road thrill, a car that could just as eas­ily be driven flat out in a 24-hour en­durance race as it could be taken down to the shops.

That phi­los­o­phy has con­tin­ued through ev­ery in­car­na­tion of M-car – all pro­duced at the BMW M divi­sion plant – through straight six nor­mally as­pi­rated and V8 nor­mally as­pi­rated mo­tors to to­day’s twin-turbo straight six.

To­day’s M3 and M4 (yes, there’s been a bit of re­nam­ing, with the 3 for sedan and the 4 for coupe) are ev­ery bit as rad­i­cal as the E30 ver­sion was in its day, ex­cept that the dif­fer­ences be­tween the M ver­sions and the ev­ery­day 3 Se­ries cars have be­come even more pro­nounced, with more spe­cialised parts and even more high tech equip­ment.

I was at Taupo for the Aus­tralasian launch of the new M3 and M4, and in be­tween do­ing laps of the cir­cuit, man­aged to chat with BMW M Divi­sion head of sales op­er­a­tions man­age­ment Jorg Bar­tels, who had flown over spe­cially to be with the Me­dia at the event.

Jorg is about as pas­sion­ate about the M con­cept as any­one can be. And he em­pha­sises that M cars are not just mod­i­fied ver­sions of stan­dard pro­duc­tion cars. “They are de­signed to de­liver max­i­mum power per­ma­nently,” he said. “The en­gine is un­com­pro­mised and high revving, yet de­liv­ers high torque from 1,850rpm, and has full race ca­pa­bil­ity.”

And it’s not just the big changes that make the dif­fer­ence, such as fit­ting light­weight yet strong car­bon fi­bre parts in key ar­eas that are im­por­tant, but less-ob­vi­ous com­po­nents, such as hubs made from spe­cial high-strength steel, and cut away to re­duce weight with­out los­ing strength.

Not some­thing you’d no­tice, but vi­tally im­por­tant in par­ing-down the un­sprung weight so the sus­pen­sion re­acts bet­ter, quicker, faster.

Many peo­ple thought BMW had aban­doned its love af­fair with straight six en­gines in the M3 when the pre­vi­ous (fourth gen­er­a­tion E90 se­ries) cars were in­tro­duced with a high-revving four-litre V8 pro­duc­ing 309kW/400Nm. The cars sounded so good that noth­ing was go­ing to re­place them.

But the cars were fuel-ef­fi­cient enough for en­gines with such high power and torque, but maybe not enough for the new gen­er­a­tion of BMW driver who de­manded great econ­omy to go with his high per­for­mance.

How­ever, BMW had another ace up its sleeve. It had also in­tro­duced a 335i model to its range of “shop­ping” three Se­ries, com­plete with a straight­six turbo-charged 3-litre en­gine pro­duc­ing 225kW of power and 400Nm of torque, the lat­ter at a very low 1,200rpm in a big fat plateau go­ing up to 5,000rpm. Hmmm – that’s equal to the V8 M3, but from much lower down the torque curve.

Bet­ter yet, it has su­perb fuel econ­omy and great drive­abil­ity.

So it was to this en­gine that the BMW M

en­gi­neers fo­cused their at­ten­tion for the new F80 ver­sion of the M3 (and M4).

Most peo­ple might have thought that just tweak­ing the turbo would have given it enough power to match, or ex­ceed, the E90 V8 out­put. But that’s not the way BMW M en­gi­neers think. In­stead, the whole en­gine was ex­am­ined in fine de­tail to en­sure it would be able to meet the cri­te­ria; a road car dur­ing the week, maybe a race car at week­ends.

The en­gine in the 335i (and in other BMWs end­ing in 35i, such as the 235i and 435i) has what BMW calls TwinPower tur­bocharg­ing, the “twin” com­ing from the fact that it has a twin­scroll tur­bocharger de­signed to cut turbo lag and de­liver high torque from the bot­tom of the curve, and high power at the top.

But to get the power they wanted, the M-sters de­cided to fit two mono-scroll turbos, one for each bank of three cylin­ders, to give an in­ter­fer­ence-free gas flow to the tur­bocharg­ers via a 120 de­gree crankshaft an­gle.

Hav­ing en­sured the power out­put (and ex­tra) torque, the en­gi­neers then de­cided to make the en­gines more heat-ef­fi­cient, as well as lighter. So they threw away the idea of hav­ing cast iron lin­ers to the cylin­ders in the alu­minium block, and in­stead de­vel­oped a process of elec­tric arc wire di­rectly spray­ing into the cylin­ders.

This re­sults in per­fect ad­he­sion, and much bet­ter heat dis­si­pa­tion, as well as sav­ing about 2kg.

Other en­gine com­po­nents to fol­low were the crankshaft, which has high tor­sional rigid­ity, and is forged to make it stronger, light­weight pis­tons, a dou­ble flow oil pump in the wet sump to en­sure oil sup­ply is al­ways de­liv­ered at 100 per­cent no mat­ter what the de­mands of the en­gines.

And to top it off, and again, im­prove heat dis­si­pa­tion while los­ing weight, a mag­ne­sium al­loy sump is fit­ted.

“Some 75 per­cent of the new en­gine is M parts, and only 25 per­cent nor­mal BMW parts,” said Jorg.

The net re­sult of the en­gine changes are that the per­for­mance is out­stand­ing, with a very flat torque curve, yet the abil­ity to go to high revs when re­quired.

Be­cause max­i­mum torque is avail­able from less than 1,800rpm, this means the driver has full power avail­able im­me­di­ately af­ter chang­ing up a gear, even from the en­gine max­i­mum of 7,300rpm, giv­ing a truly lin­ear power de­liv­ery.

This is max­imised by the dou­ble clutch gear­box, and its abil­ity to change gear faster than most hu­mans.

the en­gine – so where does it go? The an­swer: a big­ger ra­di­a­tor, with an ex­tra ra­di­a­tor for the trans­mis­sion, and two charge air cool­ers for the in­ter­cooler. That power bulge on the bon­net of the new cars is def­i­nitely there for a rea­son – the en­gine won’t fit with­out it.

Then to the ex­haust sys­tem. It’s got to han­dle more gas flow, so it’s big­ger, but made of lighter steel. But the best thing is that the en­gi­neers re­alised the new car has to SOUND right, yet tur­bocharg­ers tend to chop up ex­haust sound and make it qui­eter.

To solve the prob­lem, an elec­tri­cally-ad­justable ex­haust flap is fit­ted, and lets out a bril­liant sound­track when the en­gine is be­ing driven in anger, while damp­ing down noise as you creep your way down your street late at night.

The M3/4 are fit­ted with a seven-speed dou­ble clutch gear­box, com­plete with var­i­ous modes to ei­ther make it eas­ier to drive, or to de­liver rock­et­pro­pelled gear changes (in­clud­ing launch con­trol if you want to get away from the lights faster than any­one else), and this too, has been given the M treat­ment, plus there’s a light­weight drive shaft and Ac­tive M dif­fer­en­tial, which feeds in the power as needed.

“In the sus­pen­sion, ev­ery­thing be­tween the wheels, and the wheels them­selves, is lighter and stiffer,” says Jorg, “and lighter weight is one of the rea­sons why we opted for non-run­flat tyres on the M3 and M4.”

So we see a sus­pen­sion which con­sists of an alu­minium dou­ble-joint spring strut axle at the front, and an alu­minium five-link rear axle, with alu­minium con­trol arms and wheel car­ri­ers, a rear axle sub frame in light­weight steel, rigidly bolted to the body, and M-spe­cific kine­mat­ics and rigid­ity set-up. The lighter weight of the rear sus­pen­sion cuts another 3kg off the M cars’ weight.

The stan­dard brakes fea­ture four-pis­ton fixed­caliper vented and per­fo­rated discs at the front, twin-pis­ton fixed caliper vented and per­fo­rated discs at the back, but for those who want to go even fur­ther, a ce­ramic disc set-up can be spec­i­fied.

Steer­ing sees a vari­able M Sport electro­mechan­i­cal rack and pin­ion, with vari­able ra­tios and an over­all ra­tio of 15 to 1. And even the steer­ing wheel has been given the slim­ming process – it’s made of light­weight mag­ne­sium, and is 8mm smaller in di­am­e­ter than the stan­dard wheel.

The light­weight forged al­loy wheels are dif­fer­ent front and rear: nine inch wide at the front, 10 inch at the back, in 18 inch di­am­e­ter, and shod with 255/40 and 275/40 rub­ber re­spec­tively.

Fi­nally, the car­bon fi­bre parts. In our July 2014 is­sue I de­scribed the lat­est BMW elec­tric i3 and i8 cars, which have car­bon-fi­bre re­in­forced plas­tic (CFRP) bod­ies, made in a new spe­cialised BMW plant, and the avail­abil­ity of this in­dus­tri­alised process has been utilised by the M en­gi­neers. The pre­vi­ous M3 was fit­ted with a CFRP roof, and this has been car­ried over to the new car, com­plete with a CFRP roof bow. Net re­sult; lower cen­tre of grav­ity. How­ever, the new cars also get a one-piece CFRP drive­shaft, which is not only lighter, re­duc­ing ro­tat­ing mass, but also more rigid, both of which gives bet­ter ac­cel­er­a­tion and re­spon­sive­ness.

The boot lid is made from a car­bon-fi­bre shield mould­ing com­pound with an in­te­grated spoiler (for im­proved down­force at high speed), and it cuts another 5kg.

High per­for­mance ve­hi­cles are of­ten fit­ted with a steel strut brace which fits be­tween the two sus­pen­sion tur­rets, over the en­gine, to pro­vide more tor­sional stiff­ness. How­ever, the BMW en­gi­neers de­vised a more el­e­gant so­lu­tion (forced in part by the height of the in­ter­cool­ers on top of the en­gine), with a U-shaped brace which is an­chored front and rear, and passes each side of the en­gine, and in front of it.

Also made from CFRP, it im­proves steer­ing pre­ci­sion and ac­cu­racy, and in­creases front end rigid­ity, but weighs only 1.5kg.

The new cars’ bon­net and side panels have come in for the weight-loss treat­ment, too, and are made of alu­minium, cut­ting 16.6kg off the to­tal weight. And alu­minium is the weight-saver used in the front axle and alu­minium shear panel; weight loss 3kg.

And in­side the car, the seats have been light­ened by 12kg, and the seat frames by 6kg.

Whew! The net re­sult as far as the en­gine changes are con­cerned is that power is now raised to 317kW, while torque leaps by a mas­sive 150Nm to 550Nm. This re­sults in a 0-100km/h ac­cel­er­a­tion fig­ure of only 4.1 sec­onds (with top speed elec­tron­i­cally lim­ited to 250km/h).

And yet at the same time fuel con­sump­tion has dropped dra­mat­i­cally, with an over­all av­er­age of 8.3L/100km!

Says Jorg: “The M is al­ways the M, and it is al­ways the very top model of BMW.” We have to agree!

The BMW M4 leads the M3 at Taupo

En­gine com­part­ment show­ing the el­e­gant CFRP strut brace

En­gine cut­away

One of the big turbos READER RE­PLY 0140828

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