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A840iPetrolvsB125dDiesel
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  • PerformancePerformance0-100, top speed
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  • Specs840i · 125d

BMW 840i Convertible G15 vs BMW 125d F20LCI: which is truly faster?

Simulated drag race 0 → 1,000 m in real time. Synchronised speed counters and stopwatch. Physics calibration on 7 manufacturer measurements.

limousine · 2021 vs 2018 · Methodology
BMWPetrolFaster

840i Convertible G15

333 hp · 500 Nm · 1,840 kg · 2021

VS
BMWDiesel

125d F20LCI

224 hp · 450 Nm · 1,480 kg · 2018

Result · 0–100 km/h

ABMW 840i Convertible G15

5.57 s

Gap0.91 sin favour of 840i Convertible
BBMW 125d F20LCI

6.48 s

Summary · Caralogy simulation
Measure840i Convertible G15125d F20LCIGap
0–100 km/h5.57 s6.48 s0.91 s · 840i Convertible G15
400 m standing start13.79 s14.68 s0.89 s · 840i Convertible G15
1,000 m standing start24.82 s26.40 s1.58 s · 840i Convertible G15
Top speed (electronically limited)250 km/h240 km/h10 km/h · 840i Convertible G15
Power-to-weight ratio5.53 kg/hp6.61 kg/hpbetter ratio · 840i Convertible G15

Watch the race

Standing-start drag race, calibrated on manufacturer splits. The gap shows at each stage.

BMWPetrol840i Convertible G15
Speed
0km/h
Timer
0,00s
Distance
0m
BMWDiesel125d F20LCI
Speed
0km/h
Timer
0,00s
Distance
0m
100 m
200 m
300 m
400 m
500 m
600 m
700 m
800 m
900 m
1000 m
0m → 1000m
Gap0m

Stage-by-stage comparison

Simulated performance at each stage. Best value in bold.
Stage840i Convertible G15125d F20LCI
0–30 km/h1.54 s1.88 s
0–50 km/h2.50 s3.03 s
0–80 km/h4.11 s4.83 s
0–100 km/h5.57 s6.48 s
0–120 km/h7.39 s8.57 s
0–160 km/h12.34 s14.58 s
0–200 km/h19.98 s25.23 s
400 m standing start13.79 s14.68 s
1,000 m standing start24.82 s26.40 s
Top speed limited250 km/h240 km/h

Parameters and assumptions

Simulation

Start
Standing, straight line
Surface
Dry asphalt, 23°C
Wind
None
Driver
1 person, 75 kg

Calibration

Splits
0–100, 0–200 manufacturer
Power curve
Real measurement (Caralogy)
VMax
Manufacturer limited
Transmission
Losses integrated in model

Physics model calibrated on manufacturer splits. The limited top speed is not the real aerodynamic top speed of the vehicles.

Under the bonnet

Manufacturer technical specifications. The power-to-weight ratio is the key physical factor in a drag race.

BMW

840i Convertible G15

5,53kg/hpratio better by 1,08 kg/hp
CharacteristicValueDetail
Power333 hp6 cyl
Torque500 Nm
Weight1 840 kgmanufacturer kerb weight
Drivetrain-
Gearbox8-speed Steptronic
BMW

125d F20LCI

6,61kg/hpcompensated by −360 kg
CharacteristicValueDetail
Power224 hp4 cyl
Torque450 Nm
Weight1 480 kgmanufacturer kerb weight
Drivetrain-
Gearbox8-speed Steptronic

The start: 0 to 100 km/h

Off the line, the 840i Convertible hits 100 km/h in 5.57 s versus 6.48 s for the 125d. At this point, the 840i Convertible leads by 0.91 s and sits roughly 12 m ahead.

From 100 km/h to 400 metres

At 200 metres, the 840i Convertible is doing 136 km/h against 130 km/h for the 125d. The gap is 0.65 s. The challenger starts to claw back ground.

At 400 metres standing start, the 840i Convertible crosses the line in 13.79 s versus 14.67 s. The 0.88 s gap represents roughly 39 m of track - a gap visible to the naked eye.

Beyond 400 metres: top speed comes into play

Past 400 metres, the 840i Convertible continues to build its lead. At 600 metres, it runs at 190 km/h versus 180 km/h. At 1,000 metres, the 840i Convertible finishes in 24.82 s versus 26.39 s, with a 1.58 s lead. Both vehicles have similar top speeds (250 (i.e. 155 mph - industry threshold) vs 240 km/h), preventing any comeback.

What the numbers don’t tell you

Both rivals are electronically governed, but not at the same level: the 840i Convertible is capped at 250 (i.e. 155 mph - industry threshold) km/h, the 125d at 240 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 (5.53 kg/hp vs 6.61 kg/hp) and transmission (Automatic vs Automatic).

In European road use (130 km/h max), both vehicles reach the legal speed limit in under 9.81 seconds. The 0.91 s difference in 0 to 100 km/h is mostly felt in motorway merging and overtaking.

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Frequently asked questions

Over 0–100 km/h, 840i Convertible G15 wins (5,57 s vs 6,48 s).

840i Convertible G15 goes from 0 to 100 km/h in 5,57 seconds (calibrated simulation).

840i Convertible G15: 333 hp, ratio 5,53 kg/hp. 125d F20LCI: 224 hp, ratio 6,61 kg/hp.

840i Convertible G15: 250 km/h. 125d F20LCI: 240 km/h.