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in search of the ultimate hybrid powertrain

Over the last 18 months a working group within IP has been asking the question "what would be the ultimate high-volume hybrid system?" Two guiding principles were adopted:

  • A responsive, no-compromise Powertrain suitable for commuting, sporty driving or towing a caravan 600 miles in a day to the Alps.
  • Maximum customer fuel consumption reduction for a given electrical content

One of our concepts, called Pi-hybrid, includes a PHEV mode and offers the potential to reduce fuel consumption for a "C" class vehicle by more than 50% with only 4kW.hr / 60kg of electrical storage and a 25kW / 25Nm electrical machine.

Mechanically the system is positioned at the interface of the engine and a conventional manual or DSG transmission. A key element for which we have developed unique IPR is the means for transitioning between e-drive and conventional modes rapidly and without discernable driveline disturbance.

The performance enhancement and e-drive operating modes are also different from other hybrids.

Performance enhancement mode

Most hybrid systems gain a substantial amount of their fuel economy benefit by enabling the use of a smaller engine. This is normally done by taking energy directly from storage and applying it through powerful electrical machines when peak demand is required. As with our SuperGen i-hybrid system the Pi-hybrid achieves similar results whilst using only very small amounts of stored electricity in order to enhance the responsiveness of a boosting system. Consequently full performance is always available irrespective of battery condition. This approach reduces the size and cost of the electrical machinery required and leaves more stored energy for e-mode operation.

e-drive mode

Increasing the proportion of drive energy provided electrically can produce large "well-to-wheels" CO2 reductions whilst allowing strategically important flexibility in how the energy is produced. This is leading to high levels of interest in PHEVs but, since electrical energy storage is costly and heavy, it is important to maximise the benefits. The Pi hybrid system enables rapid, shock-free transitions into and out of e-drive at speeds of up to 120 km/h whilst the adaptive control system makes use of the fact that most fuel is used on repetitive journeys of less than 80km to actively tune the conditions under which e-drive is invoked.