New Volkswagen Polo BlueGT with cylinder deactivation offers gasoline engine fuel economy of up to 52 mpg US
6 March 2012
|Polo BlueGT. Click to enlarge.|
Volkswagen introduced the new Polo BlueGT at the Geneva Motor Show. The technical highlight of the compact car is its cylinder deactivation system—introduced for the first time in a Volkswagen—known as active cylinder management or ACT. The system was realized with the new 1.4-liter gasoline-fueled TSI of the Polo BlueGT.
The TSI develops a power output of 103 kW / 138 hp, with a combined fuel consumption of 4.7 l/100 km/h (50 mpg US), equivalent to 108 g/km CO2. If the Polo BlueGT is ordered with the optional 7-speed dual clutch gearbox (DSG), fuel consumption drops further to 4.5 l/100 km (52 mpg US), equivalent to 105 g/km CO2.
With a top speed of 210 km/h (130 mph), the car accelerates to 100 km/h in 7.9 seconds. This combination of efficiency and dynamic performance is enabled by the systematic interplay of ACT, downsizing (reduced engine displacement plus direct injection and charging) and BlueMotion Technology (Stop/Start system, battery regeneration). As such, the Polo BlueGT closes the gap between the Polo 1.2 TSI (77 kW / 103 hp) and the Polo GTI (132 kW / 177 hp). The new car will be on the market in July.
The 1.4 TSI in the Polo BlueGT is the top engine of the entirely new EA211 series of petrol engines. These gasoline engines and the EA288 series diesel engines, which are also new, are technological pillars of the future Modular Transverse Matrix (MQB). (Earlier post.) One property shared by all of these engines is an identical mounting position in the car.
|Cylinder deactivation. Click to enlarge.|
Volkswagen is the first carmaker to introduce active cylinder management as a fuel-saving technology in smaller engines—they were previously only known in larger eight or twelve cylinder units. Shutting down the second and third cylinders under low- and medium-load states reduces fuel consumption in the EU driving cycle by about 0.4 l/100 km. In constant speed driving at 50 km/h (31 mph) in third or fourth gear, fuel savings are as much as one liter per 100 km. But even when driving at 70 km/h (43 mph) in fifth gear, fuel consumption is still reduced by 0.7 l/100 km.
ACT becomes active at engine speeds from 1,250 to 4,000 rpm, and at torque outputs from 25 to approx. 100 N·m (18 to 75 lb-ft)—a broad swath of the operating map that includes nearly 70% of all driving states in the EU driving cycle.
When the driver presses the accelerator pedal, the two cylinders are imperceptibly reactivated. Even with two cylinders, the balanced 1.4 TSI of the Polo BlueGT runs just as quietly with as little vibration as it does when all four combustion chambers are active, Volkswagen says. All mechanical switchover actions are completed within one half of a camshaft revolution; this only takes between 13 and 36 milliseconds, depending on engine speed. The transitions are smoothed by supporting interventions to the ignition and throttle valve.
Using an accelerator pedal sensor and intelligent monitoring software, the system can also detect non-uniform driving profiles—such as while driving through traffic or in a sporty manner when driving on a country road. In such cases, cylinder shutoff is disabled. The driver is informed whether two or four cylinders are active by an indication in the multifunction display located between the speedometer and tachometer.
To further reduce emission and fuel consumption values and improve torque in the lower engine speed range, the intake camshaft was designed to be adjustable over a range of 50 degree crank angle on all EA211 engines; in the 1.4 TSI of the Polo BlueGT, an exhaust camshaft adjuster is added. It adjusts to the desired spread of control times, thereby ensuring more spontaneous response from low revs; at the same time, it also improves torque at high revs.
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