1 1 F O C U S with the Passat has given us a great deal of experience with the e-supercharging technology and the way in which the engine interacts with a high geared transmission.” Further projects concentrating on e-supercharging followed, among them, as part of the EU “Powerful” project (Powertrain for Future Light-duty Vehicles), was a demonstrator vehicle based on a Fiat Punto with a 1.4 l naturally aspirated engine and a 12-volt e-compressor. For the ALABC Consortium (Advanced Lead Acid Battery Consortium), two mild-hybrid demonstrator vehicles with gasoline-powered engine, e-compressor and belt-driven starter generator were developed and set up in 2010 and 2013. In the more recent demonstrator, the voltage level of the used lead-carbon batteries was raised to 48 volts. AVL’s latest concept vehicle with electric supercharging – currently still in development – is the VW Golf TGDI “High Efficiency Demonstrator.” This vehicle is being developed to demonstrate that by using a Miller- cycle engine and an exhaust gas recirculation system positioned close to the cylinder and pumped by an e-compressor, CO2 emissions can be reduced from standard 122 g CO2/km down to 90 g CO2/km – without requiring any kind of hybridization measures. engines,” says Paul Kapus. OEMs are additionally moving towards harmonized engine families, allowing for a single base engine to cover a growing performance spectrum for very different types of vehicles. Another key driver for the development of turbocharged gasoline engines is that customers are demanding higher torque at lower speeds. There are several ways to charge an engine, e. g. with a mechanical compressor, a gasdriven turbocharger or – as AVL has successfully shown in several demonstrator vehicles – with a combination of turbocharger and e-compressor. EXTENSIVE EXPERIENCE WITH E-COMPRESSORS AVL started to focus on electric supercharging more than ten years ago in the context of a customer project. Back then, in 2006, the VW Passat “Low Consumption TC” demonstrator vehicle was engineered at AVL to demonstrate that a gasoline engine was capable of achieving fuel economy comparable to that of a diesel engine. For this to be achieved, the Passat’s 2l GDI engine was fitted with a small gas-driven turbocharger, delivering high torque even at low speeds, and combined with a high geared transmission. The envisaged target to achieve fuel economy similar to that of a diesel engine was met. In further stages of the development, a cooled exhaust gas recirculation system and an e-compressor were added. Requiring as little as 0.3 seconds to reach full boost, the e-compressor eliminates turbo lag during start-up. “To accomplish this,” Paul Kapus explains, “the e-compressor only needs to remain switched on for about one second to build up about 400mbar of boost pressure on the compressor side. All in all, working > Alfa Giulietta AVL TGDI high-performance demonstrator > Fiat/Alfa Romeo 1.75 l high-performance turbo engine producing 350 hp Photos: Volvo, AVL, Fiat/Alfa
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