MBTech Unveiled CNG-Powered SLK

MBTech, an engineering group with close ties to Mercedes-Benz, has unveiled a compressed natural gas (CNG) sports car study, based on a Mercedes-Benz SLK-Class.

The engineers from MBtech's powertrain solutions segment have achieved a considerable increase in performance with the four cylinder compressor engine in the series SLK model in the course of the CNG adaptation.

The CNG demonstrator from MBtech possesses more than 146 kW and a maximum torque of 270 Nm, which accelerates the SLK from a standstill to 100 km/h in 7.8 seconds. It has a top speed of 244 km/h.

The key to the design of MBTech’s new CNG system is a fifth injector, which is used to enhance the traditional four injection valves. However, this does not inject the gas selectively into the cylinders but rather into the central air intake. This enables the delivery of the quantities of gas required for the high cylinder performance even in the event of strongly fluctuating gas quality.

In addition, the MBtech specialists also took over the development of additional engine electronics - thus the CNG SLK also possesses an innovative sensor/actuator unit as an application tool in addition to the gasoline control unit.

In combination with the pistons specially adapted to the specific characteristics of CNG fuel and an adapted turbo charger translation, this ensures that the CNG engine not only runs smoothly in every situation but even better in fact: Nonetheless, the technology carrier possesses an impressively low level of CO2 emission: Its CO2 emission of 150 grams per kilometer (NEDC) is comparable with current compact cars.

It requires only 5.6 kilograms of CNG per 100 kilometers. However, the natural gas SLK not only demonstrates fuel consumption far below that of a comparable gasoline engine in the moderate speed ranges of the NEDC consumption cycle but also at full throttle. The reason: The natural gas engine developed by MBtech omits high-consumption component protection typically utilized in gasoline engines at full throttle, consisting of additionally injected fuel which prevents components such as the catalytic converter from overheating, as a result of the combustion process designed for compact combustion. At high speeds its enormous fuel saving potential comes into full play.

As a result of the tight space requirements in a sport convertible, the engineers had to cope with a drastically reduced muffler volume. Extensive detail optimizations enabled the development of a single-pipe exhaust system which fulfills both the NVH and exhaust gas back pressures requirements.