MAHLE downsizing demonstrator

The efficiency of combustion engines will be crucial in determining energy consumption and thus CO2 emissions in transportation well into the next century. One critical instrument for increasing energy efficiency is more compact engines, known as downsizing concepts, where high-tech innovations compensate for lower displacement and fewer cylinders.

Thanks to downsizing, significantly improved consumption figures can be achieved particularly at the standardized cycle-relevant operating points. However, inefficiencies can also arise in actual operation. This is why MAHLE has calculated the actual consumption of a vehicle with its own downsizing engine developed in house for a range of road types and driving styles. The results indicate the potential for technologies to further reduce fuel consumption both in the standard cycle and in actual operation.

Downsizing has become widespread primarily in Europe, particularly for gasoline engines. It also plays a significant role in other fast-growing market regions. This technology is critical in satisfying CO2 limits, which are measured via standard cycles. This becomes possible by shifting the load points in ranges of low specific fuel consumption, i.e., toward high loads.

However, increasing specific outputs and mean pressures also conceal issues: apart from the greater stress on components, longer full-load trips and heavy transient operation have less of a positive effect on actual fuel consumption.

In order to contain the components’ thermal load, fuel injection must be increased, in part for cooling purposes. In transient operation, there is less naturally aspirated engine base torque available due to the reduced swept volume. This must be considered in the specific application in order to speed up acceleration of the exhaust gas turbocharger. This also leads to increased fuel consumption.

Depending on the vehicle type (e.g., weight), engine type, and driving style, very high discrepancies—in part—can arise between average and actual consumption for the end customer under actual operation. MAHLE is therefore investigating complementary technologies for further significant reductions in actual consumption in extreme downsizing engines.

The MAHLE downsizing demonstrator vehicle is equipped with a three-cylinder gasoline engine developed and manufactured in house. The technical data for the engine and vehicle are recorded in the table below.

Technical data for the MAHLE downsizing engine and demonstrator vehicle

MAHLE downsizing engine
Engine typeIn-line, three-cylinder gasoline engine, turbocharging, direct injection, four valves per cylinder
Swept volume [L] 1.2
Bore/stroke [mm] 83.0/73.9
Compression ratio 9.3:1
Power output [kW] 120 between 5,000 and 6,000 rpm
Max. torque [Nm] 286 between 1,600 and 3,500 rpm
Exhaust gas turbochargerBosch Mahle Turbo Systems (BMTS), single-stage exhaust gas turbocharger
Weight [kg] 125 (dry)
MAHLE demonstrator vehicle
Weight [kg] 1,575
Fuel consumption NEDC [L/100 km] 5.8
CO2 emissions NEDC [g/km] 135
Acceleration 0–100 km/h [s] 8.7
Acceleration 80–120 km/h [s] 8.9 (5th gear)
Top speed [km/h] 213
Emission level Euro 5 (Euro 6 ready)

As a result, the analysis according to road type and driving style provides important findings and confirmed that the driving style has a very significant influence on fuel consumption figures. The partly severe deviations from average fuel consumption values can be reduced by means of consumption-optimizing technologies. The data under consideration will allow MAHLE to pursue its targeted ongoing development of components and systems toward further reduced fuel consumption—both in the standard cycles and in real driving operation.

The technologies currently researched and developed by MAHLE in order to further reduce fuel consumption in modern combustion engines include, for example, cooled exhaust gas recirculation, targeted thermal management, reduction in frictional loss, the electrification of auxiliary aggregates, and optimization of turbocharging. The resulting new products will help vehicle manufacturers to meet future goals for the reduction of CO2 emissions.

The downsizing demonstrator vehicle has impressively demonstrated in actual driving operations that the latest combustion engines offer significant potential for fuel consumption savings. In order to fully harness this potential, an appropriate driving style is required together with a variety of innovative products and technologies from MAHLE.