Mercedes-Benz Adds Two Four-Cylinder BlueEFFICIENCY Diesels to GLK SUV Lineup; Potential to Meet EU6 and US BIN5 Limits
|Mercedes-Benz GLK 250 CDI 4MATIC BlueEFFICIENCY, AMG sports package exterior. Click to enlarge.|
Mercedes-Benz has added two new four-cylinder diesels to its GLK family of SUVs: the rear-wheel drive GLK 220 CDI BlueEFFICIENCY and the all-wheel drive GLK 250 CDI 4MATIC BlueEFFICIENCY. The latter features the most powerful four-cylinder diesel currently applied in an SUV. Both vehicles meet the EU5 emissions standard and have the potential to fulfill the future EU6 limits as well as the existing BIN 5 requirements in the USA.
GLK 250 CDI 4MATIC BlueEFFICIENCY. The new 2143 cc diesel engine with direct fuel injection produces 150 kW/204 hp and 500 N·m (369 lb-ft) of torque. With its high torque already present at 1600 rpm, the GLK 250 CDI 4MATIC requires 7.0 seconds to accelerate from 80 to 120 km/h (50 to 75 mph) for overtaking. Fuel consumption is 6.7 L/100 km (35 mpg US), with CO2 emissions of 176 g/km.
The new diesel features increased maximum rail pressure of 2,000 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 when electrical voltage is applied.
The new injectors are equipped with a stack of thin piezoceramic layers 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 bar.
A two-stage supercharging system comprising a small high-pressure (HP) turbocharger and a large low-pressure (LP) turbocharger makes 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 on-demand control is improved cylinder charging and, consequently, high torque even at low engine speeds along with reduced fuel consumption.
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.
The engine is mated with the 7G-TRONIC transmission.
GLK 220 CDI BlueEFFICIENCY. The economical four-cylinder diesel engine in the GLK 220 CDI BlueEFFICIENCY is another unit from this same generation of engines. It produces 125 kW/170 hp and, depending on the equipment level, consumes only between 6.0 and 6.4 liters of diesel per 100 kilometers (39.2 to 36.8 mpg US) (combined NEDC consumption, preliminary value). CO2 emissions are from 158 to 168 grams per kilometer.
Peak torque of 400 N·m (295 lb-ft) is available over a wide rev range from 1400 to 2800 rpm. 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 (127 mph).
The GLK 220 CDI BlueEFFICIENCY is also available with the 7G-TRONIC seven-speed automatic transmission as an option.
BlueEFFICIENCY. Like all BlueEFFICIENCY models from Mercedes-Benz, the two new GLK models also feature a package of measures that help to reduce fuel consumption, including weight savings achieved through the use of high strength and ultra high strength steels in the bodyshell and weight-optimized alloy wheels.
Aerodynamic side mirrors and underbody panels lower the air resistance, and newly developed 235/60 R 17 V tires reduce rolling resistance. A regulated fuel pump and the energy-saving electric power steering system further reduce the GLK’s fuel consumption. With a fuel-consumption computer and a display showing current fuel consumption, GLK drivers can check their fuel consumption at any time and adjust their driving behavior accordingly.