MAHLE Advanced Downsizing

The downsizing of engines, especially gasoline, has now become firmly established as a proven approach for delivering significant fuel economy benefits. Starting in 2007, the first generation MAHLE downsizing engine was developed using two-stage turbocharging to demonstrate the higher levels of performance which can be achieved, whilst still maintaining the inherent efficiency advantages of a small displacement unit. Key design features of the engine included:

• 3 cylinder, short stroke configuration
• 1.2 litre displacement
• Central, spray-guided gasoline direct injection
• COSCAST® cylinder head, block, bedplate and all major castings
• Low friction valvetrain and power cell
• Dual independent cam phasing
• MAHLE NIKASIL® parent bore coating in cylinders
• Split cooling system (separate head and block circuits) with electric water pump
• Through-bolting construction

This engine achieved or exceeded all its original targets with a power output very close to 200 bhp, a peak torque figure of 286 Nm, excellent flexibility (with 250 Nm available at 1,500 rpm) and a minimum Brake Specific Fuel Consumption (BSFC) of 235 g/kWh – all from a compact and lightweight 3-cylinder, all aluminium engine with a displacement of just 1.2 litres.

In order to provide a near-term production feasible solution and still deliver acceptable performance, the second generation downsizing engine was designed with a single turbocharger from Bosch Mahle Turbo Systems (BMTS). Various other modifications were made to the engine configuration including a switch to the latest multi-hole solenoid fuel injectors along with the MED17 engine management system from Bosch. This engine was further developed on the test bed throughout 2009 and some equally impressive performance figures were achieved, including a power output of 160 bhp and equivalent torque and fuel economy values to the first generation, twin-turbo engine.

The engine performance and flexibility were further optimised and the unit was installed in a production vehicle in mid 2010 to allow further driving development and calibration optimisation. A total of fourteen downsizing engines of various configurations have been constructed to date, with a number being tested and further developed at off-site locations. Certain engines are currently being used to assess the benefits of running on alternative fuels (such as ethanol and butanol blends) and to investigate future oil formulations. Robert Bosch GmbH are continuing their calibration activities to support the vehicle program and to further develop the fuel injection and engine management systems. The cylinder head and power pack from the MAHLE downsizing engine have also formed the basis for a new design of single cylinder research engine for advanced research into combustion system development. Further information on MAHLE Powertrain's downsizing experience and capabilities. Press release from Ward's Auto (June 2011)