Volkswagen turns to the Miller Cycle for improved efficiency

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VW is promising impressive efficiency improvements from its new engine

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Manufacturers are leaving no stone unturned in the quest to improve the efficiency of their internal combustion engines. Just this week, we've seen a fastidiously engineered diesel engine from Ford and a camless engine from Qoros. Now Volkswagen, no stranger to doing whatever it takes to lower consumption (figures), has joined the party by releasing a 1.5-liter Miller Cycle engine tasked with improving fuel consumption and increasing low-down torque.

Volkswagen's engineers say there are a number of improvements that come courtesy of the improved thermodynamic efficiency associated with Miller Cycle engines. An increase in the geometric compression ratio has, according to VW, allowed for improved efficiency in the load range most customers will actually use, while the final compression temperature has been lowered through early closing of the intake valve and the expansion cooling that brings.

Thanks to these improvements, VW claims its new engine offers up peak torque from just 1,300 rpm, while also improving fuel economy by 1 l/100 km (8 US MPG) compared to the current 1.5-liter TSI engine.

Working tandem with these big changes to the combustion cycle are a number of small changes that, when combined, contribute to the longevity and efficiency of the engine. On the 110 kW (148 hp) version of the engine, the cylinder liners are coated with an atmospheric plasma spray to cut down on friction, improve heat dissipation and improve corrosion resistance.

The engine's cooling system has also come under the microscope, and now will make sure the water in the crankcase and engine remains stationary while the car is warming up. As well as cutting the amount of time spent without the engine operating at ideal temperature, VW says the system helps warm the cabin more quickly on cold mornings.

Although it's usually used on high end, big displacement engines, VW has even fitted cylinder deactivation to the new engine, allowing it to run as a two-cylinder under light loads.

An increasing injection pressure 350 bar has improved the mixture formation in the engine, which should also lead to lower particulate emissions.

Interestingly, the release makes it very clear the efficiency and emissions improvements are unlikely to show up under test cycle conditions, but argues that they're likely to have a "distinct impact on the customer's everyday driving."

The new four-cylinder engine will find its way into showrooms later this year in 96 kW (129 hp) and 110 kW (148 hp) guises. It's currently on show at the Vienna Motor Symposium.

Source: VW

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