CPT/AVL Study: New Generation of Micro-Hybrid Technologies Can Enable More than 25% Reduction in Fuel Consumption at Lower Cost Than Full Hybrid Drive Systems

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


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