motor

Few race cars enjoy the reversal of fortune that BMW's M3 enjoyed over the past two seasons of the American Le Mans Series (ALMS). In 2000, the M3 race car, which is known as the M3 GTR and races in the GT class, won only once and was trounced by its chief rival, the Porsche 911. But BMW roared back in 2001, winning six of the eight races and taking the manufacturers' championship and the drivers' crown for pilot J�rg M�ller. It was an extraordinary feat considering Porsches outnumbered BMWs four to one at most races. What BMW did was replace the M3 GTR's six-cylinder engine with a V-8, which spelled more low-end grunt. A little history explains why the engine swap was beneficial. By the end of the 2000 season, the 3.2-liter six had reached a horsepower plateau after six years. The problem was the rule-mandated intake restrictor plate with its 1.7-inch-diameter hole to reduce the amount of air that enters the engine. As an engine spins faster and needs more air, the restrictor's effectiveness increases. And how! Think of breathing through a straw: You can take regular breaths through it easily enough, but start exercising and breathing hard, and suddenly, getting air into and out of that straw is tough. In the GT class, the restrictor makes a smaller, high-revving engine less effective than one with more displacement and low-end torque. Because of the bore spacing of the BMW six, the engine could not grow beyond 3.2 liters. Porsche's flat-six displaces 3.6 liters. The rules said that even though the Porsche displaced about 400 more cubic centimeters it must use the same 1.7-diameter restrictor as the BMW. Same size straw, but the Porsches had a bigger engine and, according to BMW, a huge advantage. The M3's V-8 is not a version of the engine that powers BMW street cars. It's a racing motor designed by the same BMW Motorsport branch that built the engine many believe was the most powerful Formula 1 engine in 2001, the BMW V-10. The V-8 has an aluminum block and heads, four cams, four valves per cylinder, and port fuel injection. Its 4.0-liter displacement is a huge increase over the old six's. BMW claims the new engine makes 444 horsepower, 42 more than the suspiciously low 402 figure Porsche quotes for its 911 GT3 race car and 24 more than the six-cylinder M3 racer made. The big difference is torque: BMW's V-8 makes 354 pound-feet, the Porsche 911 makes 281. A six-speed nonsynchro gearbox transmits power though a limited-slip rear differential to 11.4-inch-wide Yokohama racing slicks. The V-8 M3 uses the same basic chassis as the six. As the rules require, it's based on the stock M3 body shell. But by the time BMW has added safety-cage bars, new suspension bits, carbon-fiber bodywork, front and rear wings, and a data-acquisition system, the GTR is far closer to a purpose-built race car than a street car. We were invited for a ride at Sebring by one of the two BMW teams, Team PTG. We realized just how racy this Bimmer is as soon as we tried to get it moving. The clutch is a five-inch carbon disc that presses on a flywheel that's "only large enough to fit the clutch," says the large and imposing PTG president, Tom Milner. With such a small, light flywheel, the engine feels as if it were jacked up on amphetamines, instantly responding to prods of the accelerator. To get under way, you either do a kamikaze clutch drop or you delicately brush the throttle as you slowly release the clutch pedal. We managed to crawl out of the pits without stalling and then spent the next few laps puttering around for the photographer. On lap three, we got on the gas and blasted down the front straight to Turn One. Only Al Gore groupies will fail to slobber all over the V-8. It screams. The crankshaft is of the single-plane variety, so the usual V-8 rumble is replaced by a high-pitched guttural snarl that rips. With gearing that tops out at 152 mph, the V-8 gets the car to 60 mph in 3.4 seconds, 1.3 seconds quicker than a street M3. The engine doles out power like a turbine�eerily smooth, so smooth that on the second turn, a low-speed second-gear right-hander, we went to full power too soon, expecting the silky power band to keep the tires hooked up. Auf wiedersehen! The rear tires lit up, and the car spun. The damage was limited to the ego, so we pressed on while keeping in mind Milner's little caution: "You crash my car, I kill you!" Spin aside, the GTR is a breeze to drive. In the turns, it's as grippy as driving on fly paper. We were unable to test on a skidpad, but in a slow turn that most replicated one, our VBOX recorded 1.2 g of lateral grip. In a high-speed turn, where downforce comes into play, we recorded 1.4 g. The very grippy street M3 manages just 0.87 g. Two things impressed: rock-solid stability at high speed and amazing brakes. Going 150 was absolutely serene. Plexiglass covers both window openings, so there's no wind buffeting. As in a video game, the only indication of speed is the scenery flashing by. As for the brakes, in every measure�feel, effort, and effectiveness�they were perfect. There's no power assist, yet the pedal isn't stiff. We never got used to their immense stopping power; we'd brake way too early and have to get back on the gas to go through the turn. As sweet as the M3 GTR is, it might have proved too dominant. Last November, the rule makers told BMW it had to build 50 V-8 M3s for the street by March or carry as much as a 220-pound weight penalty and a smaller restrictor. BMW says it's built one of the European-only $225,000 street M3 V-8s and can't meet the production deadline. BMW also claims the engine and weight handicaps would make the GTR so noncompetitive that it wouldn't bother racing the car. As of this writing, BMW hadn't announced its plans for the 2002 season. Although this rules battle sounds like typical racing politics, we'd hate to see the V-8 GTR parked next season.