2004 BMW 545i vs. 2005 Cadillac STS

Variability is no problem, though, when it comes to BMW's 4.4-liter V-8. The Valvetronic engine deals with the airflow restriction of the throttle plate by eliminating it, instead controlling the amount of air ingested by the cylinders by varying valve lift electronically. Stepless variable valve timing for intake and exhaust camshafts and a fully variable intake manifold contribute to a broad, fat torque curve. Output is up, too, 35 horsepower over the previous, non-Valvetronic 4.4-liter engine. This new V-8 feels more powerful than its 325-horse rating might suggest. Part of that credit goes to the 545i's ZF six-speed automatic transmission; first gear is particularly short and gives the engine tremendous torque multiplication for launching off the line at a stoplight. There never seems to be any shortage of gear ratios for the transmission to apply to a given driving situation.

And there in lies another annoyance. One editor noted, "In brisk (but not wide-open throttle) acceleration, the engine seems to lunge from gear to gear, like a chained Rottweiler." Following a line of cars in traffic can prove difficult as well. Under semihard braking, the transmission aggressively forces downshifts, slowing the car unnaturally even after the driver has lifted off the brake pedal as the traffic begins to move again. To reduce the excessive retardation, the driver must step on the accelerator, initiating another forward lunge. Concluded one writer, "BMW needs to work on its throttle tip-in calibration and transmission phasing." Added another, "It's so hard to be smooth, especially at low speeds. Starting and stopping often come off abrupt, no matter how careful you are with the controls."