BMW 840d xDrive Convertible G15 vs Porsche Panamera 971: which is truly faster?

Off the line, the 840d xDrive Convertible hits 100 km/h in 5.06 s versus 5.28 s for the Panamera. At this point, the 840d xDrive Convertible leads by 0.22 s and sits roughly 6 m ahead.

At 200 metres, the 840d xDrive Convertible is doing 136 km/h against 136 km/h for the Panamera. The gap is 0.21 s. The gap remains stable from the start.

At 400 metres standing start, the 840d xDrive Convertible crosses the line in 13.36 s versus 13.57 s. The 0.21 s gap represents roughly 10 m of track - barely a car length.

Past 400 metres, the 840d xDrive Convertible continues to build its lead. At 600 metres, it runs at 190 km/h versus 190 km/h. At 1,000 metres, the 840d xDrive Convertible finishes in 24.38 s versus 24.66 s, with a 0.28 s lead. Both vehicles have similar top speeds (250 (i.e. 155 mph - industry threshold) vs 264 km/h), preventing any comeback.

The 840d xDrive Convertible features all-wheel drive (AWD) against the Panamera’s RWD. At low speeds (0-30, 0-50, 0-80 km/h), AWD doubles the driven contact area: all four wheels transmit torque to the road, virtually eliminating wheelspin at launch. This traction advantage is decisive in the range where the motor delivers peak torque, before power and aerodynamics take over.

Both rivals are electronically governed, but not at the same level: the 840d xDrive Convertible is capped at 250 (i.e. 155 mph - industry threshold) km/h, the Panamera at 264 km/h. This isn’t a physical engine limit - it’s a manufacturer choice, usually for tyre safety or homologation reasons. Neither car reaches its true aerodynamic top speed.

With two combustion powertrains, the difference comes down to power-to-weight ratio (5.97 kg/hp vs 5.42 kg/hp) and transmission (Automatic vs Automatic).

In European road use (130 km/h max), both vehicles reach the legal speed limit in under 8.22 seconds. The 0.22 s difference in 0 to 100 km/h is mostly felt in motorway merging and overtaking.