Land Rover offers its penultimate Range Rover Sport with a variety of powertrain options, with four, six, or eight cylinders – naturally aspirated, supercharged, turbocharged, or even hybrid. And now it's rolling out another.

The new Range Rover Sport HST packs a 3.0-liter turbocharged six-cylinder version of JLR's efficient Ingenium engine family with a mild hybrid assist to deliver 400 horsepower and 406 lb-ft of torque. More potent than the existing V6 and running on a combination of gasoline and electricity, it'll sprint to 60 mph in 5.9 seconds and top out at 140 mph.

The high-tech powertrain uses a twin-scroll turbocharged and continuously variable valve timing, combined with a 48-volt electrical system powering a start-stop ignition and an electric supercharger that can spool up to 120,000 rpm in just half a second. Along with better response and balance, it improves on the old V6's carbon emissions by 12 percent, and its particulate emissions by 75 percent.

"Inline six-cylinder engines are inherently better balanced than V6 designs and our all-new Ingenium unit builds on that promise to optimize efficiency in all operating conditions," noted JLR product-engineering chief Nick Rogers.

"Advanced features, including an electric supercharger, ensure distinctive Range Rover Sport performance and responses, while the intelligent MHEV system harvests energy to improve fuel economy and reduce emissions."

The mild-hybrid powertrain is being rolled out initially in a special edition that also features carbon-fiber accents, special badges and a suedecloth- and satin chrome-trimmed cabin. US pricing has yet to be announced, but it's available to order in the UK now for £81,250, making it slightly more expensive than the HSE Dynamic model with the similarly powerful but more electrified plug-in hybrid powertrain (but not as much as the more potent V8s).