|Reductions in fuel consumption and CO2 from base 2.0-liter ELC-Hybrid to downsized 1.4L VTES + SpeedStart. Click to enlarge.|
The mild electrification of cars using a new generation of low-voltage micro-hybrid technologies—including an electric supercharger, belt-integrated starter/generator, and a carbon-enhanced advanced VRLA UltraBattery (earlier post)—can enable existing technology engine and transmission combinations to be aggressively downsized and downspeeded to support very significant (>25%) reductions in fuel consumption and CO2 emissions, while maintaining acceptable levels of driver enjoyment, according to a study by Controlled Power Technologies (CPT) and AVL presented at AVL’s Motor und Umwelt conference last week.
The paper was jointly authored by CPT engineering director and chief technical officer Guy Morris with Mark Criddle, Mike Dowsett and Toby Heason from CPT and Dr. Paul Kapus and Matthias Neubauer from AVL.
CPT and AVL have been working for the past 18 months to develop a value-driven micro/mild HEV solution, utilizing CPT’s production-ready VTES electric supercharger (earlier post). CPT and AVL’s most recent work assesses the potential of a VTES equipped downsized ELC-Hybrid vehicle in combination with the CPT SpeedStart Integrated Starter Generator (earlier post) and the UltraBattery.
The intent is to enable aggressive yet near term downsizing and downspeeding of existing engine families, delivering proven CO reduction and fuel economy improvement, without the usual dynamic compromises that typically limit market acceptance.—Morris et al.
Based on a VW Passat family-sized saloon, the demonstrator currently incorporates a advanced, AVL-developed 2-liter gasoline engine already delivering a fuel consumption of 6.6 liters/100km (36 mpg US) and CO2 emissions of 154g/km—a 20% reduction from the 192 g/km of a series production Passat (MY 2006) fitted with a 2.0L TGDI engine and close to the 146 g/km of the current Passat 2.0L common rail TDI engine. In effect, AVL has developed a gasoline engine with diesel-like fuel efficiency.
One of the significant features of this demonstrator is its long gearing ratios to enable down-speeding of the engine. Normally this would result in unacceptable high gear vehicle acceleration, but the integration of CPT’s variable torque enhancement system or VTES provides an important dynamic performance boost, reacting instantly to transient load conditions by delivering up to 25 kW of additional power to the crankshaft in less than a second, even at the lowest engine speeds.
The next technology step is to further develop AVL’s efficient low carbon ELC-hybrid concept by incorporating CPT’s SpeedStart system. In combination with the VTES electric supercharger, this will create a cost effective micro/mild hybrid system which, when applied to a downsized 1.4-liter variant of the ELC-hybrid power unit, will meet the European industry’s 130 g/km CO2 emissions target.
The use of a carbon-enhanced valve-regulated lead-acid (VRLA) battery will help maximize energy recuperation during deceleration, fully realizing SpeedStart’s potential for high power generation and hence electrical energy recovery.
The combination of low voltage micro-hybrid technologies incorporating stop-start, brake regeneration and electric boosting—as well as exhaust gas regeneration which we’re also working on for the longer term—can help minimize the additional cost of CO2 compliance to the consumer to between €1,500 and €4,000 within the 2015 to 2020 timeframe. This compares with €6,000 to more than €18,000 for a full hybrid or electric vehicle.—Guy Morris
Guy Morris et al. (2010) A New Engine Boosting Concept with Energy Recuperation for Micro/Mild Hybrid Applications. (22nd International AVL Conference “Engine & Environment”)