BMW 120d F40 vs BMW i3s I01: which is truly faster?

Off the line, the i3s hits 100 km/h in 6.81 s versus 7.24 s for the 120d. The instant torque of 270 Nm from the electric motor makes the difference. At this point, the i3s leads by 0.43 s and sits roughly 7 m ahead.

At 200 metres, the i3s is doing 124 km/h against 123 km/h for the 120d. The gap is 0.30 s. The challenger starts to claw back ground.

At 400 metres standing start, the i3s crosses the line in 15.05 s versus 15.38 s. The 0.33 s gap represents roughly 14 m of track - two to three car lengths.

Past 400 metres, the situation changes. The i3s maxes out at 160 km/h while the 120d keeps accelerating towards 231 km/h. At 600 metres, the gap has dropped to 0.25 s.

Around 731 metres, both vehicles are level. This is the inversion point: the 120d overcomes its launch deficit thanks to a 71 km/h higher top speed.

At 1,000 metres, the 120d finishes in 27.74 s versus 28.59 s. The 0.85 s delta in favour of the 120d shows that top speed makes a clear difference.

Both rivals are electronically governed, but not at the same level: the 120d is capped at 231 km/h, the i3s at 160 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 11.29 seconds. The 0.43 s difference in 0 to 100 km/h is mostly felt in motorway merging and overtaking.