Diesel v Gasoline v Hybrid: Which Is the Quickest Tuned BMW Over the Quarter-Mile?

When the M-ification of BMWs began, almost every model had an ‘M-wannabe’ variant. M340i, M340d, M550d, and so on. Setting aside all personal hatred toward this sacrilege that would have been punished by burning at the stake in times long ago, the M-three-numbers cars are a tad more performant than the regular models. But just how much better, exactly? That’s a question for carwow’s team of hot-headed characters – and they already have the answer.

Not surprisingly, they lined up a trio of BMW M340i, M340d, and a non-M 330e, a plug-in hybrid. However, the answer in the previous paragraph lies under the limitations of a minor aftermarket detail. All three cars have been tuned, so the outputs differ from what Munchen’s finest originally planned.

The M340d Touring ( ‘station wagon,’ in BMW jargon) relies on the tried and tested three-liter straight-six diesel. Thanks to its stage one upgrade, the car fires up 430 hp (some 436 PS) and 627 lb-ft (850 Nm) of turn-the-crank wizardry. All that power goes to all four wheels via an 8-speed automatic gearbox. Because it’s a diesel, the engine is made of heavier aluminum alloy, and the extra roofing over the cargo bay adds some additional weight, too, for a body mass of 1,945 kg (4,288 lbs).

That’s a full 187 kg (412 lbs) over the M340i sedan (1,758 kg / 3,876 lbs) sitting next to it at the start line of the quarter-mile drag race. The engine in this gas guzzler is displacing three liters, just like the diesel, and it also has six-in-a-row cylinders. Thanks to a tune-up, it puts out 470 hp (477 PS) and 465 lb-ft (630 Nm), again spread to all four wheels via an eight-speed transmission.

The best of both worlds comes from the plug-in hybrid 330e that sports a two-liter turbo engine with just four cylinders that team up with an electric motor to spin the rear wheels. That’s the first drawback for the non-M BMW in this race. The second is the total system output: 400 hp (405 PS) and 516 lb-ft (700 Nm). The eight-speed automatic driveline seems to be the norm for this three-way bout, and the hybrid adheres to this paradigm.

One possible advantage of the 330e is the weight – 1,740 kg (3,836 lbs) but given the bhp/ton ratings and the two-wheel drive propulsion, it shouldn’t make much difference. However, the electric boost might turn out to be the ace in the sleeve of the underdog.

A famous racer once said, ‘Horsepower sells cars, but torque wins races.’ Well, maybe in an apples-to-apples comparison, but not at this track in the UK where the BMW face-off is staged. Diesel may be lower on power, but they’re torque lumps; there’s no denying that. Even so, the heavy 340d is constantly left behind by the 340i.

The gas-powered sedan covers the standing quarter in the shortest time (12 seconds flat), while the diesel runs three-tenths late, and the hybrid is left behind in all three rounds, with a personal best of 12.7 seconds. (Note to self: the 330e doesn’t have launch control).

Things get confusing in the rolling start races, where each car scores a win. The gasoline-only 340 gets the 50-mph start (80-kph, gearbox in automatic mode) thanks to blitz downshifts. The diesel shows its torque superiority in the 60-mph round (97-kph), starting in sixth gear and leaving the others far behind. The electro-gas mongrel takes no prisoners in the final race, with the cars in eighth gear.