Audi S6 Sportback e-tron vs BMW 840i xDrive G15: which is truly faster?

Off the line, the S6 Sportback e-tron hits 100 km/h in 4.08 s versus 4.81 s for the 840i xDrive. The instant torque of 855 Nm from the electric motor makes the difference. At this point, the S6 Sportback e-tron leads by 0.73 s and sits roughly 7 m ahead.

At 200 metres, the S6 Sportback e-tron is doing 146 km/h against 142 km/h for the 840i xDrive. The gap is 0.48 s. The challenger starts to claw back ground.

At 400 metres standing start, the S6 Sportback e-tron crosses the line in 12.52 s versus 13.04 s. The 0.52 s gap represents roughly 25 m of track - two to three car lengths.

Past 400 metres, the gap narrows. The S6 Sportback e-tron maxes out at 233 km/h while the 840i xDrive keeps accelerating towards 250 (i.e. 155 mph - industry threshold) km/h. At 600 metres, the gap is down to 0.44 s from 0.52 s at 400 metres.

At 1,000 metres, the S6 Sportback e-tron finishes in 23.58 s versus 23.66 s, with just 0.08 s to spare. The 840i xDrive fails to fully close the launch gap.

Both rivals are electronically governed, but not at the same level: the S6 Sportback e-tron is capped at 240 km/h, the 840i xDrive at 250 (i.e. 155 mph - industry threshold) 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.

Instant electric torque gives an advantage off the line. The higher top speed of the combustion engine gives an advantage over longer distances. The distance at which one catches the other depends on the top speed differential.

In European road use (130 km/h max), both vehicles reach the legal speed limit in under 7.34 seconds. The 0.73 s difference in 0 to 100 km/h is mostly felt in motorway merging and overtaking.