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While one car boasts outstanding driving performance and high fuel efficiency, the other offers high fuel efficiency and good handling. What is the difference between the two? The sporty handling dynamics set the tone in the all-wheel drive GLK 250 CDI 4MATIC BlueEFFICIENCY.

The modern, four-cylinder diesel with 150 kW (204 hp) and an impressive 500 Nm of torque guarantees top acceleration and flexibility. In fact, this model has the most powerful four-cylinder diesel engine in the SUV world. The rear-wheel drive GLK 220 CDI BlueEFFICIENCY with the familiar 125 kW (170 hp) diesel engine, on the other hand, impresses with even better fuel economy (consumption as low as 6.0 l/100 km) while at the
same time delivering great performance.

The new models underscore the leading position of the distinctive yet compact GLK. Whereas the GLK 250 CDI 4MATIC featuring permanently engaged all-wheel drive, 7G-TRONIC transmission and the segment’s most powerful four-cylinder diesel engine augments the world of top-of-the-range compact SUVs, the GLK 220 CDI with rear-wheel drive and six-speed manual transmission offers maximum fuel economy. It consumes only between 6.0 and 6.4 litres of diesel fuel per 100 kilometres and combines these low consumption values with good performance. The rear-wheel drive vehicle accelerates from zero to 100 km/h in 8.5 seconds and reaches a top speed of 205 km/h. The GLK 250 CDI4MATIC completes the sprint to the 100 km/h mark in 7.9 seconds and doesn’t stop accelerating until reaching 213 km/h. This sports car-like performance does not come at the typical cost of higher consumption. The diesel consumes only 6.7 litres per 100 kilometres on average.
GLK 250 CDI 4MATIC: The fun yet frugal power SUV
The GLK 250 CDI 4MATIC BlueEFFICIENCY brings the world’s most powerful four-cylinder diesel engine for an SUV to the Mercedes-Benz range. The new 2143 cc diesel engine with direct fuel injection produces 150 kW/204 hp and 500 Nm of torque in the GLK for outstanding performance. Just as impressive as the sprint times and the top speed is the GLK’s top-gear acceleration. Thanks to its high torque, which is already present at 1600 rpm, the GLK 250 CDI 4MATIC accelerates powerfully when overtaking, requiring only 7.0 seconds for the sprint from 80 to 120 km/h. In spite of its great performance, this GLK model is very economical to drive, consuming only 6.7 litres of diesel fuel on average per 100 kilometres (combined NEDC consumption, preliminary value). This makes the GLK significantly more fuel efficient than comparable models in this performance class. The vehicle produces CO2 emissions of 176 grams per kilometre.Furthermore, it not only meets the EU5 emissions standard but also has the potential to fulfil the EU6 limits as well as the BIN 5 requirements in the USA.

Diesel engine with advanced common-rail technology
One of the hallmarks of the new diesel engine in the GLK 250 CDI 4MATIC BlueEFFICIENCY is the increased maximum rail pressure of 2000 bar. This increase in pressure potential is a prerequisite for increasing engine output and torque while at the same time significantly reducing untreated emissions. Newly developed piezo injectors take advantage of the fact that piezoceramics change their crystal structure – and therefore their thickness – in a matter of nanoseconds (one nanosecond = one billionth of a second) when electrical voltage is applied. The new injectors are equipped with a stack of thin piezoceramic layers (called the “piezo stack”) to enable them to achieve a sufficient overall stroke from the very small stroke per layer. The injector needle is actuated directly, so that the fuel injection can be adjusted even more precisely in line with the current load and engine speed situation. Another key factor behind the low emissions, low fuel consumption at full load and peak output is the ignition pressure of 200 bars, which puts the four-cylinder diesel at the head of the field when it comes to diesel engines for passenger vehicles.

A two-stage supercharging system comprising a small high-pressure (HP) turbocharger and a large low-pressure (LP) turbocharger ensures that the optimum charging pressure is always available. The two turbochargers are connected in series, and each has a turbine and a compressor driven by this turbine for the combustion air. The HP turbine is located directly at the exhaust manifold and initially allows exhaust gas to flow through it, causing it to rotate at up to 215,000 revolutions per minute. The HP turbine housing features an integral bypass duct, which can be opened or closed by means of a wastegate triggered by a vacuum unit. If the flap is closed, the entire exhaust stream flows through the HP turbine so that the exhaust gas energy is initially available to drive the HP turbine. This allows the optimal boost pressure to be developed even at low engine speeds. As the engine speed increases, the wastegate opens, distributing the exhaust gas energy to the turbines with optimum efficiency. Downstream of the HP turbine, the two exhaust gas streams reconverge, and the remaining exhaust gas energy drives the LP turbine at a maximum speed of up to 185,000 revolutions per minute. At intermediate engine speeds, the wastegate of the HP turbine is opened so wide that the HP turbine ceases to perform any appreciable work. This allows the full exhaust gas energy to be directed with low losses into the LP turbine, which then does all of the turbine work.

The two compressors are likewise connected in series and are in addition connected to a bypass duct. The combustion air from the air filter first flows through the low-pressure compressor, where it is compressed as a function of the LP turbine’s driving power. The compressed air then flows into the high-pressure compressor, which is coupled to the HP turbine, where it undergoes further compression for a genuine two-stage supercharging process.

The key benefit of this intelligent, on-demand control is the improved cylinder charging and, consequently, high torque even at low engine speeds. What’s more, fuel consumption is reduced. During normal operation, the advantages of this concept can be seen in the harmonious driving characteristics with no turbo lag, a good torque curve across the entire engine speed range, spontaneous throttle response and noticeably improved performance. As a logical supplement to the turbocharger system, Mercedes-Benz installs a larger intercooler that reduces the temperature of the compressed and heated air by as much as 140 degrees Celsius so that a larger volume of air can enter the combustion chambers.

The newly developed exhaust gas recirculation valve (EGR valve) works like a rotary disc valve and precisely controls the quantity of fresh air and recirculated exhaust air to effectively reduce emissions of nitrogen oxides.

Text and Pictures: Daimler

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