Electrically supercharged gasoline engine achieves diesel levels of CO2
By Mike Hanlon
May 5, 2009
May 6, 2009 We have previously written about the potential of UK-based Controlled Power Technologies' (CPT) electrically driven supercharger and that potential came closer to realization this week when CPT and the world’s largest independent developer of vehicle powertrains, AVL List GmbH (AVL), unvelied a jointly developed gasoline engine that retains all the strengths, develops more power and at the same time reduces CO2 levels to that of an equivalent diesel powertrain.
The AVL demonstrator vehicle incorporates an advanced 2-liter, 4-cylinder engine with gasoline direct injection (GDI), double cam phasing and single-scroll, waste-gated turbocharger to deliver high power and torque outputs of 200PS and 400Nm respectively. A system of cooled, external exhaust gas recirculation (EGR), Lambda =1 operation at all engine loads up to 4,000rpm and advanced thermal management further enhance the CO2 reduction potential of the powertrain.
The philosophy of ‘down-speeding’ is fully employed through the fitment of gear ratios more normally associated with turbocharged diesel engines. Successful down-speeding relies heavily on the immediate availability of high torque levels at very low engine speeds in response to driver inputs. The integration of CPT’s variable torque enhancement system or VTES supercharger technology virtually eliminates all perceptible turbo-lag even in the absence of variable geometry turbine technology normally fitted to turbocharged diesel engines.
Through careful integration of the above technologies and the implementation of engine stop-start and smart alternator control, AVL is able to demonstrate CO2 emissions of just 159g/km for a VW Passat demonstration vehicle at 1,590kg vehicle mass, which also meets Euro 5 emission standards. By way of comparison, a series production Passat emits 165g/km when fitted with a 2.0l TDI (170PS) diesel engine and 194g/km when fitted with a 2.0l TFSI (200PS) gasoline engine.
At the same time the 200PS engine delivers high levels of performance & refinement whilst VTES ensures outstanding transient response even at the lowest engine speeds, equivalent to a naturally aspirated engine of twice the capacity.
“Getting a gasoline engine to deliver the lower CO2 emissions of a diesel engine is something of a holy grail for the motor industry,” says Nick Pascoe chief executive officer CPT. “The challenge is to retain the driveability at low engine speeds in order that drivers can fully realise the benefits of down-speeding. An electric supercharger can react instantly to these transient load conditions, delivering up to 25kW of additional power at the crankshaft in less than a second.”
CPT’s VTES supercharger technology benefits from almost a decade of research and continuous product development resulting in a robust and cost-effective system. Formed two years ago as a management buy-in funded by private venture capital, the company is backed by a number of prominent investors specializing in the ‘Cleantech’ energy and environmental sectors. CPT’s core competencies include power electronics, control software and the application of electrical machines to vehicle powertrains.
The AVL demonstrator will be available for test drives at the International Vienna Motor Symposium, where the technological achievements of the vehicle will be included in an opening presentation entitled ‘Future Powertrain Systems in a Fast Evolving Global Environment‘ to be delivered by Prof. Dr h.c.H.List, chairman and CEO of AVL.
The two-day symposium opens tomorrow at the Congress Centre Hofburg in Vienna. The symposium serves as a rallying point for the international world of automotive powertrain engineering, when future legislation and the latest innovations in engine development are presented in a large number of papers.