Automotive Engineering - April 2021 - 24
Optimizing hybrids
FOR COST AND
EFFICIENCY
48V Hybrid
Dimensions
ICE Variant
ICE Power Density
High Power
100kW/1
Very High Power
120kW/1
NA
45 - 55kW/1
Mid Power
80kW/1
Miller
WG-TC
Miller + VVL + VCS
VGT TC
Miller + VVL + VCS
Electric boosted TC
NA Atkinson
>40% efficiency
Miller
TC
Bore x Stroke
Common long-stroke layout
Key Dimensions
Crankcase
Bore pitch, Block height, skirt depth,
Valve diameters and positions, Cylinder head height, inlet and exhaust flanges
Casting
Machining
Components
Cylinder
Head
Table 2: Engine
component
commonality.
400V Hybrid
Mid Power
70-80kW/1
Reduced MB dia
NA Port, IEM
TC Port & Chamber, IEM
Casting
TC Port & Chamber, IEM
Machining
Crankshaft
Standard
Pin width & Oil Supply for VCS
Friction reduced
(smaller bearings)
Conrod
Standard
VCS / Variable Compression System
Lightweight
Piston
High CR
CR Variable
High CR, lightweight,
min. friction rings
Valve train module
DOHC DVVT
2-step intake VVL
DOHC DVVT
Oil pump
Mechanical
Mechanical + Electric-VCS
Mechanical
water pump
Mechanical
Electric
Electric
FEAD
Standard
Standard
Beltless - electric A/C and Vacuum
Crankcase and cranktrain
The crankcase structure must address both mechanical and thermal
loads considering gasoline engines with high power density and hence
high thermal load as well as peak firing pressure requirements of 150
bar (2,176 psi) for future knock-free combustion. Due to the significant
weight advantage, aluminum is proposed with and open deck structure.
For engine variants with variable compression ratio, the conventional connecting rod is replaced by the VCS variable conrod. In this
case, adaptation of the crankshaft (conrod journal width) is required
as well as the addition of the hydraulic control system including electric booster oil pump and pressure accumulator as shown in Figure 6.
Figure 8: The 100 kW/L performance variant of the modular
engine includes variable compression ratio and variablegeometry turbocharging.
In addition to these concept features, further measures that could be incorporated with minimal changes to the production and assembly lines, even for existing production facilities, including:
* electronically controlled thermostat/coolant temperature-management module
* second-order mass balancing shafts with roller
bearings (Figure 5)
* friction reducing coatings (piston rings, piston pins)
* camshaft roller bearings (1st bearing)
* switchable high performance water pump (lowfriction seal, efficiency-optimized impeller)
24 April 2021
A modular architecture with compact base cylinder head and separate cam carrier module permits the standardization of the main interfaces such as cylinder head height or camshaft positions. This approach, while also saving costs and weight, provides flexibility for the
application of different variability of the valvetrain systems (Figure 7)
without modifying the cylinder head itself. The base cylinder head
with combustion chamber, gas exchange ports and cooling jacket has
a cooled, integrated exhaust gas manifold with compact routing.
Cylinder head cooling for turbocharged engines with higher power
density requires special attention. A top-down cooling concept developed specifically for 4-valve cylinder heads features two cooling
jackets in the cylinder head, joined by efficient cooling jets between
the exhaust valves of each cylinder.
The base variants of the represented engine family possess switchable water pumps with map-controlled thermostat. A fully variable
thermo-management module allowing zero flow at low, part-load
operation is mandatory for future high efficiency concepts.
For electrification variants with 48V, an electric water pump becomes an attractive alternative, providing true on-demand flow and
AUTOMOTIVE ENGINEERING
BOTH IMAGES: AVL
Cylinder head, valvetrain and cooling
Automotive Engineering - April 2021
Table of Contents for the Digital Edition of Automotive Engineering - April 2021
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