What is it?
The latest addition to BMW’s 7-series luxobarge range, the new 740d is Munich’s biggest performance diesel.
Although it sounds like it should be a V8, this is actually the first BMW to run the twin-turbocharged version of Munich’s latest all-aluminium, 2993cc diesel six.
This car isn’t powered by the same 282bhp iron-blocked engine that you’ll find in a 535d, then, but a lighter and even more efficient unit with BMW’s third-generation common-rail direct injection technology and much of its Efficient Dynamics trickery too. It produces 301bhp and 443lb ft of torque.
What’s it like?
This latest diesel Seven is good for 0-62mph in 6.3sec and 155mph flat out. It’ll also return fuel economy on the right side of 40mpg, and emits just 181g/km of CO2. BMW claims that all of those figures are class-leading, and we can’t fault them. So is it as impressive off the spec sheet?
We sampled the new 740d on challenging roads in the Scottish highlands and, although those roads were narrow and more undulating than many on BMW’s development routes, the big BMW put in a very good performance indeed.
Its advantage over a 730d in terms of outright shove isn’t huge; we drove back to back with the less powerful diesel, and weren’t overwhelmed by the step up in performance. Where the 740d does score over its cheaper sibling, though, is in its sharper throttle response, greater torque at low revs and greater power high up the rev range. It’s much quicker to react when you flex your right foot than a 730d, and piles on pace through the gears in effortlessly brisk fashion.
The performance and economy improvements have been made on this engine in several ways. Diesel is now injected at 2000psi for more efficient combustion, and Munich’s Efficient Dynamics tech means the alternator, and other power-draining ancillaries, can disengage under acceleration, allowing more of the engine’s power to be fed to its wheels.
But the most significant change relative to the old twin-turbo diesel six comes on the smaller of the engine’s two turbochargers, which has variable vanes to improve response at low revs. As a result, peak torque comes in at just 1500rpm; you get 30lb ft less twist in a 535d, and not until 2000rpm.