In April 2008, Mercedes-Benz announced a tuning competition based on the new GLK-Class, which was to be launched in January 2009. Four companies were selected for the challenge. The companies inputted their own ideas and design into the GLK and the results had been revealed at Specialty Equipment Market Association (SEMA) Show.
Inspired by the winged, unlimited-class rally cars of the famed Pikes Peak Hill Climb, RENNtech set about creating a GLK that could master the pack and leave the rest chewing gravel. But, this wild GLK has a few surprises beneath its menacing exterior.
Hybrid powertrains are generally associated with fuel efficiency and lower emissions. However, RENNtech has taken one more benefit of the hybrid principle to turn the GLK into a formidable performer.
By combining an electric motor in parallel with the 3.5 litre V6 petrol engine, RENNtech has been able to capture the impressive torque that characterises electric motor drives, adding 54 Nm to enhance the GLK’s performance off-the-line and out of corners. Using a hybrid drive in a hill climb setting has the added advantage of maintaining thrust at higher altitudes, when internal combustion engines – which depend on ambient air – start to wheeze.
The specialist Mercedes tuning company has also worked its magic on the base 3.5 litre V6 unit, using components from the latest Mercedes-Benz high-performance 3.5 litre V6 Sport engine. These include a special intake manifold, cams and cylinder heads, to which RENNtech has added its own long-tube headers, composite air intake and RENNtech ECU software. Engine output is up to approximately 350 hp, augmented further by the electric motor from the hybrid drive.
The additional 72 volt drive is run by 12 volt plug-in batteries. RENNtech had a nickel-hydride solution with regenerative charging for additional range.
It is also worth noting that, despite the performance enhancements, RENNtech has succeeded in improving the fuel economy of the Rally Racer compared with the original version, “proving that high performance and efficiency can coexist,” adds Feyhl.
Bearing in mind that the Rally Racer is built for speed on tough terrain, RENNtech opted to forego creature comforts, cutting the weight of the standard GLK by removing most of the sound insulation and replacing the Mercedes-Benz seats with lightweight carbon-fibre buckets. Engineers also fitted a full roll cage and moved several components towards the rear of the vehicle to create an almost perfect 50:50 front/rear weight distribution for improved handling on tight, demanding rally stages.
Another significant handling modification comes from the custom coil-over suspension. Made to RENNtech specifications by suspension supplier KW, the package allows for adjustments in height, rake, damping rate, camber and toe-in.
Extra stopping power is provided for the Rally Racer courtesy of an in-house RENNtech brake combo featuring massive 412mm, 2-piece rotors with 8-piston callipers at the front, and 356mm discs grabbed by 4-pot callipers at the rear.
Lightweight 20 inch 3-piece, 5-spoke RENNtech wheels in a “Sniper Gray” anthracite finish, clad in NT05 275/40 20 Nitto rubber at the front and NT05 315/35 20 at the rear, fill the prominent wheel flares that underscore this GLK’s performance potential.
Although extensive exterior revisions were made to accommodate the larger wheels and brakes and to widen the track, the focus of bodyshell modifications was enhanced aerodynamic efficiency. RENNtech used the latest in Computational Fluid Dynamics (CFD) software to develop the package. The front splitter, rear diffuser and lower side skirts help direct airflow underneath the GLK Rally Racer to reduce drag and produce added downforce, while improving high speed stability at the rear.
The rear wing elements also serve an important aerodynamic purpose and add emphasis to the aggressive edginess of the original GLK design. From a visual perspective, RENNtech engineers successfully melded their aerodynamic modifications with the flared wheel arches to create a powerful side line that highlights the dynamic thrust of the Rally Racer.
