Mahle is developing a complete “fits all, off-the-shelf” modular hybrid-drive propulsion system for a wide range of automakers’ models, designed to cut costs, improve packaging and provide a level of electrified-vehicle commonality not seen before in the auto industry.
Designated Mahle Modular Hybrid Powertrain (MMHP), the system is modular, scalable and dual-mode (parallel and series) – and could be in production within two years, ready to power anything from compact sedans to hefty SUVs. The MMHP integrates an all-new turbocharged gasoline internal-combustion engine in 2- and 3-cylinder forms, customizable gearbox (one-, two- or four-speed) and a compact but powerful (choice of power/torque) electric traction motor.
The integrated system, incorporating commonality of parts, is being launched at this week’s Frankfurt Motor Show.
A fit for several current vehicle platforms as well as those at concept stage, Mahle’s MMHP can deliver an all-electric driving range of 80-100 km (50-62 mi) depending on battery-pack capacity, while the entire gasoline-electric range is up to 500 km (311 mi). The engine has achieved specific fuel consumption figures of 207 g/kWh in early-stage testing. This is expected to drop to 195g/kWh in lean operation, helped by Mahle’s Jet Ignition (MJI) pre-chamber combustion system.
Adrian Cooper, Mahle’s head of new technology, told Automotive Engineering in an exclusive pre-announcement interview, “OEMs want to reduce the number of powertrain variants and achieve greater commonality across all their vehicle platforms. As they increasingly consider electrification, many do not have the scope for the development needed for individual powertrains. So the ability to match an OTS [off-the-shelf] modular powertrain to a broad range of products, from compact B-segment sedans to large J-segment SUVs is just what they are looking for.”
Other companies are considering similar solutions, but Mahle is confident that it is in the lead with a system that can be tailored to a broad spectrum of applications. The MMHP project was started a year ago and a rapid prototype now is in the final stages of build and testing of individual components is underway. Cooper stressed that a major strength for Mahle is that it is able to design, build and supply—via its group business units—almost all aspects of the system with all core elements, including power electronics, tailored to specific requirements: “We are not buying in anything major.”
The company said the MMHP powertrain will be future-proofed from the early 2020s to meet the European Union’s stringent average fuel consumption and emissions legislation for 2030 (when fleet-average CO2 emissions must be 59.4 g/km) and beyond.
A challenge for a wide-ranging, cross-industry powertrain application is meeting requirements for OEMs that regard their ICEs as providing marque identities—i.e. brand character—via aural and throttle-response signatures. Cooper does not regard this as a problem for the market at which the MMHP is aimed, although active sound-generation and noise-cancelling could be used if necessary. “What drivers will really like is the instant pull away from low speed and the high torque delivery,” he said.
The MMHP promises to enhance potential performance. Weight of the complete hybrid powertrain is similar to that of a current 4-cyl. 2.0-L gasoline engine with manual 6-speed transmission. “The advantage of the modular system incorporating an ICE is the ability to reduce battery-pack size to achieve a usable range for the customer, 400-500 km. For our powertrain with a battery pack giving an 80 km electric range, we will achieve an equivalent CO2 figure of 18 g/km—well below targets,” said Cooper.
Significant engine cost savings
The decision to omit the option of 3-speed transmission for the MMHP was based on a pragmatic choice. It would have all the complexity of a 4-speed with only “one cog saved;” the single-speed, two-speed and four-speed transmissions are regarded by Mahle as being better options.
Capacity of the 2-cyl. engine is 1.0-L and the 3-cyl. is 1.5-L. “Mated to the hybrid powertrain, we could design the ICE to have a more limited operating range than that of a typical current engine,” explained Cooper. “It has allowed us to simplify the engine but still achieve a very good efficiency level.”
Designed exclusively for hybrid applications, the engines use the passive MJI system consisting of a small prechamber, housing a conventional sparkplug, fitted within the engine’s primary combustion chamber. It generates hot radical jets that create a very brief combustion event within the engine’s cylinder, facilitating a high compression ratio and high exhaust gas recirculation rate; these combine to reduce fuel consumption and emissions. Use of port fuel injection and a single overhead camshaft controlling just two valves per cylinder without variable valve control, keeps down unit cost. Savings for the engines alone are estimated at up to 30%.
The Frankfurt Motor Show was deemed important for the project. Said Cooper: “There and elsewhere later this year, we need to gauge reaction to the system to see if other OEM companies would like to engage with us in a program to develop the product for their specific requirements.”
With regard to applying the MMHP to current conventional platforms, Cooper said there would mostly be a question of battery sizing: “Whatever the application, no matter what operating range the powertrain is in, it has been designed to always deliver seamless performance and consistent and effective operation as a dual-mode system. Its scalability and modularity allow it to provide what we regard as a unique application of highly cost-effective flexibility for the future.”Continue reading »