Although their model names kick off with the letter M, the M340i and M850i aren't proper M cars. They're classified as M Performance vehicles, meaning that M3 and M8 are noticeably more capable in the corners and in a straight line.
CSL AutoTime of Thailand has pitted the M Performance siblings against one another to see which one's better in the quarter mile, and – somewhat anticlimactically – the answer is M850i xDrive. With CSL AutoTime host behind the wheel, the V8-powered Bimmer clocked a best of 11.94 seconds at 187 kilometers per hour (116 miles per hour).
The far less powerful and torquey M340i xDrive managed a very respectable 12.66 seconds at 175 clicks, meaning 109 miles per hour in the United States and the United Kingdom alike. Considering that said times were achieved on a runway instead of a drag strip, they're all the more impressive.
Had the cars been allowed to max out, both would have stopped gaining speed at 250 kilometers per hour (155 mph) due to the factory limiter. The generally accepted – and hideously simplified - rule is that power gives you speed and torque gives you acceleration, meaning that the M850i xDrive would outperform the M340i xDrive in a straight line.
Emphasis on hideously simplified because tires, gearing, launch control, aero performance, and many other things make a world of difference in terms of maximum speed. Curb weight, however, favors the D-segment luxury sedan at 1,670 kilograms (3,682 pounds) compared to a ponderous 1,890 kilograms (4,167 pounds) for the 8 Series.
Photo: CSL AutoTime on YouTube
Codenamed G15 for the coupe, this generation of the 8 Series serves as the replacement for the third-generation 6 Series. Aesthetically a far cry from the original 8er, the G15 is the flagship coupe in the Bavarian automaker's lineup. The problem is, the first units rolled off the assembly line in 2018.
The easiest way of telling how old the G15 is? Popping the hood reveals the N63 twin-turbo V8 rather than the S68 engine that BMW introduced in April 2022 with the facelifted X7 M60i luxury sport utility vehicle. Compared to the S63 and N63, the newcomer features many changes, of which the most important is electrification. All versions of the S68 come with a level of electrification, beginning with a 48-volt starter generator in the X7 M60i.
Mild-hybrid assistance comes by default in the M340i for model year 2025, as well as the 2.0-liter turbo four-cylinder 330i. For some reason or another, BMW M has yet to update the M4's twin-turbo sixer with the belt-driven starter generator.
All-wheel drive by default, the 2025 BMW M850i xDrive Coupe presently starts at $106,300 in the United States market. As for the M340i Sedan, the MSRPs are $57,600 with rear-wheel drive or $59,600 with all-wheel drive. CLAR-based Bimmers with xDrive feature an electronically controlled multi-disc clutch that continuously splits torque between the rear and front wheels.
After a 1:43 scale model of a Ferrari 250 GTO sparked Mircea's interest for cars when he was a kid, an early internship at Top Gear sealed his career path. He's most interested in muscle cars and American trucks, but he takes a passing interest in quirky kei cars as well. Full profile
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