For years at Volkswagen, talk of efficiency improvements almost always involved TDI?the badging that denoted VW?s diesel technology, now effectively mothballed in the United States because of the company’s costly emissions scandal. It?s no surprise that this week at the Vienna Motor Symposium, the automaker showed several different paths that it sees leading to carbon-neutral mobility?with no mention of TDI.
One of these is the VW Golf TSI BlueMotion, powered by a new 1.5-liter TSI (turbocharged, direct injection) gasoline four-cylinder engine fitted with what the company describes as an ?affordable micro hybrid system.?
What that amounts to is essentially an engine stop/start system with a significantly broader operating range. The new BlueMotion system employs the seven-speed version of VW?s DSG dual-clutch automatic transmission. If you lift gently off the accelerator, it simply declutches and disables the engine at speeds up to 81 mph. The setup is a little more complicated than it sounds, as it requires a higher-capacity battery?here a compact lithium-ion one?to handle the vehicle’s electric loads during long engine-off coasting stints. The battery is managed alongside a traditional lead-acid one, with a special Q-diode to isolate vehicle systems from the starter circuit. Three methods are used to restart the engine: by use of its starter motor, by re-engaging the clutch to crank the engine, or by combining the starter with clutch engagement. Although th...