Parallel two-clutch systems, dubbed “P2”, enable the efficient separation of a hybrid’s electric motor and its gas engine which results in similar efficiency of current hybrid two motor systems without the need for two separate engines. This could result in cost savings of 30% or more for hybrid car buyers.
Honda’s fleet of hybrids uses a one-motor system, the Integrated Motor Assist, which has the gas engine and electric motor bolted together and engaged with a single clutch. In this configuration, the electric motor runs simultaneously with the gas engine. The P2 clutch enables the gas engine to shut down, transferring the load to the electric motor. The efficiency of selective electric motor use is gained without the costly addition of a separate electric motor.
The 2011 Hyundai Sonata Hybrid and the Infiniti M353 Hybrid are the first hybrids to use the new parallel-clutch P2 system. According to Hyundai, the new design results in greater highway fuel efficiency and improved electric motor performance. With the separate clutch, the electric motor can be increased in size to deliver greater acceleration.
The P2 also results in improves regenerative braking, and saves costs by eliminating the need for a torque converter. Cost of batteries for P2 hybrids is expected to be about 30% lower than current costs for electric can batteries.
By 2025, the US fleet average could reach 60mpg, with SUVs averaging 40mpg
Manufacturers who have not yet committed to the two-motor system currently in most hybrids, or to Honda’s Integrated Motor Assist design, are benefiting from their late entry into the hybrid market. Mercedes and BMW have P2 hybrids in development, as well as Hyundai, Volkswagen and Infiniti. John German, senior fellow with the International Council for Clean Transportation, believes that the P2 hybrids will enter the mass market, and that the new technology will “become standard on vehicles.”
German believes that by 2025, the US fleet average could reach 60mpg, with SUVs averaging 40mpg.
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