SpeedRacer Posted December 31, 2001 Share Posted December 31, 2001 Cut this from Popular Mechanics and Car & Drivers web pages: "THROTTLE FREE GAS ENGINE" "As befits a flagship, BMW's still-to-be-introduced new 7 Series is a road- going "wundercar." One of its most stellar breakthroughs is the new V8 engine. Smaller, lighter and both 14 percent more powerful and 14 percent more fuel efficient than the previous car's engine, the V8 boasts BMW's Valvetronic system that does away with the conventional throttle valve. Instead of a butterfly valve in the engine's intake tract to control airflow, Valvetronic regulates intake air by adjusting valve lift. The more the intake valves open, the more air enters the engine, allowing more fuel for more power. BMW claims that by removing the obstruction of the throttle valve, there is at least a 10 percent fuel savings. A true drive-by-wire system, Valvetronic relies on electric motors—one at each cylinder bank—to drive an eccentric shaft that acts on intermediate camshaft followers. These followers take the form of levers between the intake cam and each cylinder's pair of intake valves. As the driver steps on the gas pedal, a computerized signal tells the electric motors how much to twist the eccentric shaft. This varies the amount the intake valves open. During normal operation, the size of the valve opening ranges from about 0.5mm to 2.0mm. Along with Valvetronic, the engine's intake is also tuned by a variable manifold that uses an electric motor to constantly change the length of each cylinder's intake runner according to load and other conditions. The engine also features BMW's existing bi-Vanos variable valve timing system, which changes the timing of both intake and exhaust valve openings and closings. The 4.4-liter V8 to be introduced in the new 745i is currently rated at 333 hp and 332 ft.-lb. of torque. And yes, BMW rounded off the displacement to 4.5—the car's name sounds better that way. VARIABLE-LENGTH INTAKE Intake manifolds within variable-length runners can broaden an engine's torque curve. Because the ideal intake-runner length varies with rpm, some engines alternate between two and three runner lengths. BMW takes this one step further by using intake runners whose lengths can vary infinitely between 9.1 (blue arrows) and 26.5 inches (red arrows) by rotating a sleeve inside the plenum through 110 degrees. The sleeves feeding the right and left cylinder banks rotate in opposite directions." Ya gotta see it because it's amazing. There is an article and pictures in the January 2002 issue of Road & Track. Those guys in Bavaria are thinking out of the box again. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted January 3, 2002 Share Posted January 3, 2002 Yea the engine is cool, but take a look at the tranny... HE HE HE Quote Link to comment Share on other sites More sharing options...
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