Volvo's most important new technology is Drive-EÂ - E as in efficient, E as in environment. It's a clean-sheet design, a four-cylinder engine family that can be modified for diesel or gasoline, just not in the same car. The gasoline version coming to America starts with a turbocharger and delivers a reasonable 240 hp, it's called the T5 engine. Adding the supercharger jumps the engine up to 302 hp, that's the T6.
In case you're not clear on the functionality: the supercharger supplies immediate acceleration, the turbocharger sustains the rush. Both can force air into the engine intake manifold but the supercharger runs off a belt connected to the engine. Step on the throttle, the supercharger engages instantly, and pressurized air flows to the engine right away with zero lag. It's great for starting up from standstill.
The more common turbocharger technology takes a couple tenths of a second to reach full output because you need more exhaust gas to create more revolutions. Exhaust gas spins up an impeller while a separate, connected impeller forces fresh air into the engine. More exhaust gas spins things faster. At full boost, up to twice as much air is entering the engine as when it's sucked in with no help. The supercharger buys time while the turbo spools up, then it cuts out.
Does Drive-E work? Absolutely. The T6 engine with both blowers and an eight-speed automatic gets to 60 mph in 5.6 seconds. In a Volvo! It feels like a six- or eight-cylinder engine. The turbo-only T5 car is a half-second slower and gets 37 mpg highway, 25 mpg city. The T5 is 20% more fuel-efficient on the highway than Volvo's previous five-cylinder (also confusingly called the T5). Volvo claims the new engine to be the world's cleanest combustion engine car relative to power. Specifically, at 302 hp and 148 g/km of CO2, it delivers 2 hp per gram of CO2.
To save fuel, the ECO+ feature lets the engine shut down at very low speeds; it's stop-start where the engine stops turning before the car stops moving. Other ECO+ settings let the car coast from 31 down to 19 mph (50-30 kph) with your foot off the gas and use the air conditioner with less aggressive settings. All this is important to Volvo's buyer demographic that skews more liberal and earth-friendly than virtually any other car brand.