Toronto Star

Fewer cylinders, more power, less weight

Fifth-generation M series may be the most radical and technicall­y advanced

- Jim Kenzie

MUNICH, GERMANY— The fifth-generation M3 (and the first M4 — the coupe is now called the 4 Series) may represent the most radical upgrades in the sub-marque’s history.

Due on our shores next spring, the cars may also be more different from their donor cousins than ever before. The changes centre on powertrain, suspension, and lightweigh­t body engineerin­g.

The increasing cylinder count (four in generation 1, six in gens 2 and 3, eight in gen 4) and displaceme­nt (2.3, 3.0 and 4.0 litres) of the M3 line are both reversed, yet power and torque continue their inexorable rises.

It’s back to a 3.0-L inline six with double overhead camshafts. Add twin turbos, and it sounds like BMW engines of the recent past. But the new M motor is, in fact, all-new, and unique to these two cars.

Power is up marginally, from 414 in our current M3 to about 430. Torque rises substantia­lly, to a peak of 369 lb.-ft., 30 per cent more than before.

And never has the term “torque plateau” (as opposed to torque curve) been more appropriat­e — that peak value is achieved at under 2,000 r.p.m., and it stays there to nearly 6,000.

All this with fuel consumptio­n re- duced by 30 per cent, to approximat­ely the same level as the firstgener­ation M3 of 1986, with its sub-200-horse, 2.3-litre, four-cylinder. That, my friends, is progress. Converting even this reduced amount of gasoline into this amount of power generates considerab­le amounts of heat. We counted something like eight separate heat exchange units in this car, including high- and low-temperatur­e engine radiators, the turbo intercoole­rs, an oil cooler, a cooler for the optional dual clutch transmissi­on, and the air conditione­r.

The M3 has always been a trackready car you can drive on the street.

Making it a turbo for the first time presented a challenge for the track aspect of its performanc­e — the dreaded turbo lag.

In order to ensure that engine response can be immediate upon applicatio­n of the throttle, the boost wastegate has been engineered so that when you lift off on the loud pedal, fuel is cut to the cylinders but the turbos keep spinning. When you bang down on the pedal again, in goes the fuel, the turbos are still spooled up, and away you go.

Atotal of10 kg has been taken out of the engine. That doesn’t sound like much when going from a V8 to a six. But the turbos, intercoole­rs, etc., all add up.

Still, it is weight off the front axle, helping maintain the ideal 50/50 front/rear weight distributi­on.

Indeed, weight reduction was a big part of the new M3/4’s developmen­t everywhere, the goal of a sub-1,500- kg car being attained, depending on level of equipment — about 80 kg less than a comparable outgoing model. The former car featured a carbon fibre roof on the coupe; this is now offered on the sedan as well. The M4 coupe rear deck lid has a carbon fibre structure, bonded to a sheet moulded compound skin. But under certain lights, the join between the two surfaces could be seen. In an interestin­g case of cooperatio­n between styling and engineerin­g, the stylists came up with a slight depression in the deck surface; the edges of this little valley coincide with where the bonding is underneath, rendering the joins invisible. Clever. A major chunk of weight was taken out of the centre of the car — the driveshaft is now a carbon fibre tube. It is so stiff it can now be a one-piece design, thereby eliminatin­g the centre support bearing required in the former two-piece steel design. The lower rotating mass means less inertia, meaning power transfer to the rear axle is more immediate. A carbon fibre strut brace connecting the front shock towers to the radiator shroud weighs only 1.5 kg, and improves front-end stiffness and steering response.

New aluminum suspension control arms, hub carriers and axle subframes save another 5 kg, and provide even sharper handling.

As noted, a seven-speed dual clutch transmissi­on with integrated launch control is an option. The base transmissi­on is a new six-speed manual with rev matching function for up- or downshifts, which weighs a remarkable 12 kg less than its predecesso­r. Transporta­tion for freelance writer Jim Kenzie was provided by the manufactur­er. Email: wheels@thestar.ca.

 ?? JIM KENZIE FOR THE TORONTO STAR ?? The redesigned BMW M4 is powered by a new 3.0-L inline six-cylinder twin-turbo engine, which boosts power to 430 hp and torque to a peak of 369 lb.-ft. But it also reduces fuel consumptio­n by 30 per cent.
JIM KENZIE FOR THE TORONTO STAR The redesigned BMW M4 is powered by a new 3.0-L inline six-cylinder twin-turbo engine, which boosts power to 430 hp and torque to a peak of 369 lb.-ft. But it also reduces fuel consumptio­n by 30 per cent.
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