REVIEWS: 2008 BMW M3

March 19, 2007
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Never mind that the confrontation is a year away; the shooters are already vying for high ground. Knife fighters know better than to show up at this bazooka battle. Contenders armed with anything less than a hot V-8 will be blown to smithereens.
Audi made that clear by rolling out its direct-injected 4.2-liter RS4 packing 420 hp. Lexus is finally mounting a serious challenge with the upcoming "more-than-400-hp" IS-F sport sedan. Mercedes-Benz recently retired its C55 AMG to clear the decks for a new C63, scheduled to bow later this year. Cadillac's second-generation CTS-V, powered by a strapping 6.2-liter V-8, is due next year.
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That leaves BMW. Twenty years ago, when this brand mustered the gumption to offer a sport coupe equally at home on road or racetrack, a tide of elation washed over every car enthusiast in the land. Two years ago, the buzz about a new M3 with V-8 power began.
Those who worship the Bimmer bible saw it in the scriptures. The second-generation E36 upped the cylinder count from the original four to six in the early 1990s. A displacement boost from 3.0 to 3.2 liters arrived for 1996. BMW's M department began shipping its incendiary S54 six--333 hp, 8000-rpm redline--in the third-generation E46 M3, launched in 2001. It didn't take a prophet to deduce that the E92 coupe, which rolled forth last fall with a muscular twin-turbo six under its hood, was also engineered to host a V-8.
At the Geneva show, BMW finally ac-knowledged what everyone already knew by presenting a supposedly conceptual M3 and hints about its engine. The new 4.0-liter V-8 is a derivative of the remarkable 5.0-liter V-10 that powers today's M5 and M6. Both powerplants share an architecture that includes aluminum-block-and-head construction, a 90-degree V-angle, a 3.6-inch (92-mm) bore, a 3.0-inch (75-mm) stroke, 3.9-inch (98-mm) bore spacing, and a 12.0:1 compression ratio.
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Like the V-10, the new V-8 block is a low-pressure die casting made of an aluminum alloy with a high silicon content. The lowly Chevrolet Vega used the same material thirty-six years ago for the same reasons that BMW selected this approach. The weight and complexity of iron cylinder liners are avoided because silicon is sufficiently tough to serve as the bore surface. A honing procedure polishes the hard silicon crystals that precipitate out of the molten aluminum during casting. To improve the wear resistance of the oil-cooled, cast-aluminum pistons, their skirts are plated with a thin coating of iron.
The V-8 block's bottom is reinforced by a stiff aluminum and iron bedplate that keeps the forged-steel crankshaft happy at its work. Under that, there's a dual-sump oil pan straddling the car's steering and structural components. An extra pump transfers lubricant from the front reservoir to the main storage sump at the rear, where the oil is sucked up to serve as the engine's lifeblood with no loss of pressure when the driver flings the M3 through the inevitable high-g maneuvers.
Cylinder heads embody Formula 1 practices, in no small part the result of BMW's team-ownership role in top-echelon motorsports. Two chain-driven hollow camshafts bear directly against the hydraulic bucket-type tappets that open four valves per cylinder. Computer-controlled drive mechanisms vary intake and exhaust event timing on cue to optimize smoothness, output, and combustion efficiency over the full operating range. Each pair of short, straight intake ports is fed by one fuel injector, one close-coupled servo-activated throttle, and a molded-plastic air trumpet.
The astute engine aficionado will notice a couple of minor technological lapses here. The first is the old-fashioned indirect (into the port, not the combustion chamber) fuel injection. While BMW has several four-, six-, and twelve-cylinder direct-injection engines, that technology has not yet graced the company's gasoline-powered eights and tens. Another venial crudity is the use of speed-density calculations for airflow, versus the more precise mass-measurement method. Calculating in-stead of measuring intake flow, however, avoids the restriction imposed by a mass-air meter in the induction system.
The M3's powertrain control computer will offer two control programs: normal and extra spicy. One innovation BMW developed for the V-10 and passed on to the new V-8 in second-generation form is ion-flow detonation-sensing technology. Fluctuation in the flow of charged particles across the spark-plug gaps at the onset of detonation causes variations in ignition coil current. When those variations are detected by the powertrain controller, it retards ignition timing a few degrees to halt premature combustion.
The exhaust headers that evacuate spent gases from the cylinder heads also have that unmistakable F1 look. These tightly nested, thin-wall, stainless-steel pipes are hydroformed for low restriction and minimal heat absorption. Four catalysts cleanse any nastiness that exits the engine.
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While the M department's V-8 and V-10 share most of the above features, these engines differ in certain areas. A double-row chain drives the V-8's intake cams, compared with the V-10's single-row chain, and the eight-cylinder's variable valve timing mechanisms are simpler, so the V-10's complex high-pressure oil system isn't needed. The V-8 is an even-firing design while the V-10 is not. (Equalizing the intervals between power pulses in the 90-degree V-10 would necessitate a split-pin crankshaft, an inherently weaker design that is unsuitable for ultrahigh power and rpm applications.) Thanks to the V-8's shorter, stiffer crankshaft, it benefits from an 8400-rpm redline versus the V-10's 8250-rpm limit. Power and torque peaks are spread farther apart, meaning that the 4.0-liter V-8 is the overachiever, with a torque peak of 295 lb-ft at 3900 rpm and a maximum 414 hp at 8300 rpm. (The 5.0-liter V-10 crests with 383 lb-ft at 6100 and 500 hp at 7750 rpm.) Eighty-eight percent of the M3's peak torque is available from 2400 rpm to its redline.
All this bodes well for stunning performance. Since the new V-8 is 33 pounds lighter than the 333-hp, 3.2-liter in-line six it replaces, the power-to-weight ratio is clearly moving in a positive direction. To maintain its svelte balance, the new M3 continues with a domed aluminum hood and nineteen-inch forged-aluminum wheels. The front fenders and side sills are molded plastic, while the roof is carbon fiber. (A similar panel installed on the M6 coupe saves twelve pounds.) As these factory photos reveal, the new M3's body is well-ventilated by three hungry intakes below the front bumper, two slots in the hood, a gill in each front fender, and a large diffuser in back. The dual-strut mirrors consumed hours of wind-tunnel time. The headlamps, taillamps, doors, deck lid, and glass are the only exterior parts shared with standard 3-series coupes.
BMW's transmission lab also is throwing a bone at the iconic Bimmer. The SMG six-speed, which prompted intense love-it/hate-it reactions upon its arrival five years ago, is gone. Take your pick between a conventional stick-and-pedal six-speed and BMW's first dual-clutch automatic. While purists will cringe at the thought of an automatic anything in their pet M3s, they won't whine about this new seven-speed's uninterrupted flow of power during upshifts.
So take a seat where you're safe from collateral damage. When the new M3 arrives next spring, the V-8 bombs will fly.

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Cost to Own
Depreciation
38.8%
Depreciation
$26391
Insurance
$15925
Fuel Cost
$12647
Financing
$6300
Maintenance
$4211
Repair Costs
$1940
State Fees
$650
Loss in Value + Expenses
= 5 Year Cost to Own