Automotive Engineering - April 2021 - 25

COVER STORY

significantly reducing power demand for pump actuation. applied at
all hybrid versions. For the hybrid variants the cooling system complexity further increases with cooling of the electrical components.
A pressure- and volume- flow-controlled oil pump is considered as
a baseline technology for all engine variants. Piston cooling jets are
one of the most significant consumers in terms of volume flow rate.
Demand-based control of the cooling significantly reduces oil flow
rate and associated parasitic losses in the low-load range. The integrated, controlled piston cooling that controls the oil flow rate to the
jets according to the actual operating point of the engine is therefore
a standard feature of all variants.

Technology features of performance variants
Starting with the baseline 48V-P0, three different performance levels
are proposed, with respective 80-, 100- and 120-kWL outputs. The
base variant with 80 kW/L has a 350-bar (5,076-psi) fuel injection
system and variable-geometry turbine (VGT). An external EGRsystem is part of the fuel efficiency and emission package.
The valvetrain for all variants includes continuous variable valve timing
at intake and exhaust. For the 80kW/L variant a 2-step cam switching
system at the intake is optional in combination with VGT. For the higher
ratings, 2-step valve lift is required, allowing switching between partload Miller cam and full-load cam.

AUTOMOTIVE ENGINEERING

For the 100kW/L engine variant, a variable turbo
geometry is the base variant as well. An e-VGT is an
option for this rating. The base features and the two
considered combinations of additional features are
shown in Figure 8.
Electrical support of the charging system is a mandatory feature for a high efficiency powertrain layout at
these highest ratings, considering transient operation.

48V MHEV beltless engine
The next level in powertrain electrification is a P2configuration, remaining at the 48V level but with up
to 20kW electrical power. As the powertrain configuration offers increased electrical performance, replacement of mechanical auxiliary functions by electrical
solutions becomes possible.
The simplification of the ICE auxiliary drives as well
as the enhanced demand control lead to electrification
of power steering, vacuum pump, coolant pump and
A/C compressor. A beltless ICE without auxiliary drives
would be the logical step for hybrid application.
With the electrical performance of the 48V-P2 configuration the full load curve of the ICE does not need

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Automotive Engineering - April 2021

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