Truck & Off-Highway Engineering - April 2021 - 23

POWERTRAIN FEATURE

line diesel vehicle. The payload penalty
with the 48V concept also is minimal
due to a limited increase in weight.
On the other hand, the P3 full hybrid
has the highest cost of ownership mainly from higher operating and maintenance costs not sufficiently offset by
the reduced fueling cost when compared to the 48V P3 mild-hybrid configuration.

This is a condensed version of SAE Technical
Paper 2021-01-0720, written by Mufaddel
Dahodwala, Satyum Joshi, Fnu Dhanraj,
Nitisha Ahuja, Erik Koehler, Michael Franke,
and Dean Tomazic of FEV North America Inc.
It can be ordered or downloaded from
SAE International at www.sae.org.
TOHE Eberspacher Ad 0819.qxp_1/2 Page Island 7/25/19 3:16 PM Page 1

ating the P3 mild-hybrid architecture
for Class 4-5 and Class 8 long-haul applications. Studies also will focus on
evaluating the use of a 48V belt starter
generator with a P3 mild hybrid architecture for Class 4-8 applications.

Real-world drive cycle
To this point, the analysis for the different
hybrid architectures has been conducted
on the ARB transient cycle, which has
relatively high weighting for determining
the CO2 emissions for vocational applications. However, the end user is concerned
about FC improvements and subsequent
return on investment on customer specific routes. To consider this impact, a
custom drive cycle was developed using
the GT-RealDrive feature.
The cycle was derived based on a typical operating profile experienced by a
Class 6-7 delivery truck. The cycle considered included considerable low-speed
operation during city delivery with specific times of vehicle stop. Figure 10 compares the CO2 reduction and freight efficiency improvement for both P3 configurations on real-world drive cycle.
When compared to the ARB transient
cycle, both P3 configurations show higher
CO2 reduction and freight efficiency improvements on the real-world drive cycle.
For the P3 48V configuration, the CO2
reduction improved by 2% for the realworld drive cycle when compared to the
ARB transient cycle. The higher CO2 reduction also leads to improved freight-ton
efficiency. When compared on the realworld drive cycles, the difference in CO2
improvement between the P3 mild hybrid
and full hybrid application is 3%, compared to the 6% difference when evaluated on the ARB transient cycle. These
results further highlight the importance of
considering both certification and realworld drive cycles when optimizing hybrid
architecture/component specifications.
To further evaluate the potential of a
48V mild hybrid for heavy-duty applications, future studies will focus on evaluTRUCK & OFF-HIGHWAY ENGINEERING

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Truck & Off-Highway Engineering - April 2021

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