Stock for stock, the 4S is more likely to be quicker, particularly when you bring cornering and braking into the mix. Speed isn't only about the straight line, and the 550xi can't corner or brake as well as the 4S. The Porsche also isn't speed limited. You can, of course, more easily mod the 550 with say the Dinan software which will definitely aid straight line speed but do nothing for handling, cornering and braking. There's also the question of how well a modified 550xi will be able to take advantage of the additional power unleashed by the Dinan tune. The PDK transmission in the 4S is a real performance transmission, and with the Sport Chrono the launch control delivers repeated flawless launches coupled with the ability to truly lay down the power effectively. Again, if you have the ability to pony up the price of entry - about 13K - you can if you wish also add PDCC and PTVV torque vectoring and also the ceramic composite brakes.
Originally Posted by geo3515
Not clear at all if you are talking about 550xi. Official numbers are:
550xi: 4.8s (0-100kmh)
4S: 4.8s (0-60 mph), 4.6 sec. with Sport Chrono Package Plus.
BMW and Porsche do have something in common in that their cars often perform slightly better than their official specifications, but more often than not it is Porsche that tends to sandbag to a greater degree. There are any number of tests that bear this out.
Range Rover HSE Lux, Orkney Gray, Sand interior
Porsche 911 Carrera S Convertible, Midnight Blue, 6-Speed
BMW 550i, BMW 545i
Last edited by swajames; 08-04-2011 at 10:14 PM.