BMW Direct - Injection Engines V-8 and V-10

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.

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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