In order to further optimize the fuel efficiency and productivity of construction equipment, 3 main potentials have been identified: • job site optimization • machine use optimization • machine optimization The focus of this paper is the machine optimization on the example of a wheel loader. Optimizing losses in individual components must be done, but it will not be a game changer for fuel efficiency improvement. Three areas for promising improvement potentials: • Optimizing the systems interactions • Decoupling of systems • Reduction of losses One example is shown for a total machine optimization approach: the “Reverse by Braking” function is using the machine operating brakes to slow down the machine during power shuttle instead of using the engine power. Decoupling of systems requires continuously variable transmission (CVT) functionality for the driveline. This can be achieved with hydraulic or electric CVTs. Two examples for decoupling systems are shown: the Volvo hydrostatic powersplit CVT prototype and a series hybrid wheel loader. Further future potentials are explored, while the driveline and hydraulic technology are the enablers for drastic improvements: electrified site, plug in hybrid, alternative fuels, and new machine concepts.

1. AVL International Commercial Powertrain Conference – organized by AVL in co-operation with SAE International
ICPC 2013 – 3.3
Fuel efficiency in construction equipment – optimize the
machine as one system
Gunnar Stein, Anders Fröberg, Jonas Martinsson, Björn Brattberg, Reno Filla,
Joakim Unnebäck
VOLVO Construction Equipment
Copyright © 2013 AVL List GmbH and SAE International
ABSTRACT
In order to further optimize the fuel efficiency and
productivity of construction equipment, 3 main
potentials have been identified:
• job site optimization
• machine use optimization
• machine optimization
The focus of this paper is the machine optimization
on the example of a wheel loader.
Optimizing losses in individual components must be
done, but it will not be a game changer for fuel
efficiency improvement. Three areas for promising
improvement potentials:
• Optimizing the systems interactions
• Decoupling of systems
• Reduction of losses
One example is shown for a total machine
optimization approach: the “Reverse by Braking”
function is using the machine operating brakes to
slow down the machine during power shuttle instead
of using the engine power.
Decoupling of systems requires continuously
variable transmission (CVT) functionality for the
driveline. This can be achieved with hydraulic or
electric CVTs. Two examples for decoupling
systems are shown: the Volvo hydrostatic powersplit
CVT prototype and a series hybrid wheel loader.
Further future potentials are explored, while the
driveline and hydraulic technology are the enablers
for drastic improvements: electrified site, plug in
hybrid, alternative fuels, and new machine concepts.
INTRODUCTION
As in all industries we need to perform continuous
improvements of our products in order to meet
increasing demands in varies aspects. Some of
them are: environmental care, safety, health of
operators, ease of operation, maintainability,
serviceability, easy of repair, availability of fuels,
productivity and fuel efficiency and hence total cost
of ownership (TCO). As our environmental boundary
conditions change continuously – such as: perceived
value of health and safety, environmental care, fuel
availability and price, new development of
technologies and components, competitive pressure
– new technologies become commercially viable.
The key for all technology options however is, to add
value for money to our customers and add value to
our company.
As the automotive industry is moving towards hybrid
technologies, especially electrical hybrids, the
traditional vehicle architecture is broken up. This
offers opportunities for Construction Equipment
manufacturers that develop all major subsystems
within their organization or group, as the machine
can be optimized as one system. Volvo Construction
Equipment is one of these players in the industry,
especially with the background of Volvo Truck and
Bus within the group. But also conventional machine
architectures offer opportunities for total system
optimization, if different vehicle systems are linked in
a smart way.
This paper will show benefits of 3 driveline
technology steps and their integration into the
machine on the example of a wheel loader:
• traditional powershift and torque converter
transmission
• CVT transmission
• Serial hybrid with energy storage

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Furthermore an outlook will be given in which area
further improvement potentials can be found.
FUEL EFFICIENCY IMPROVEMENT
POTENTIALS IN A WHEEL LOADER
The definition for Fuel Efficiency (FE) as used in this
paper is the following:
where the fuel efficiency (measured in tons of
material moved per liter fuel consumed), is the
productivity of the machine (tons per hour) divided
by the Fuel Consumption (FC) (measured in liter fuel
consumed per hour).
So an improvement in the Fuel Efficiency can be
achieved by increasing the productivity (fuel
consumption neutral) or reducing the fuel
consumption (productivity neutral). In reality
customers expect an improvement of both factors
simultaneously.
In marketing material the improvement potentials are
typically stated as “up to X%” saving. The real life
experience is very cycle dependent and differs from
one customer to another. The average improvement
depends largely on the application, the size of the
machine, the driving cycle, the driver, the
combination of the machine with others on the site
aso. There are many factors influencing the real
values, beyond the machine technology. Never the
less, the “up to X%” values are a good indicator to
compare technologies, as these values often refer to
similar cycles and are typically measured in
controlled environments, so relative comparisons
are possible. Each equipment manufacturer carries
out customer clinic tests, so all know where they
stand vs. competition, which allows comparing
absolute Fuel Economy values. This paper will use
the “up to X%” values to compare different
technologies vs. each other in order to understand
the technology potentials.
Volvo’s view on the potentials for Fuel Efficiency
improvement potentials in a wheel loader application
are shown in Table 1.
The FE improvement potentials are large. As
explored above, the real savings for a machine
owner during the life of the machine will depend
largely on the application and of course the on-cost
for the machine that is equipped with new
technology. In the end money counts for the
machine owners, the total cost of ownership and the
cost per ton moved material.
Site optimization Up to 30%
Machine use optimization -40% up to +40%
Machine optimization:
- Reduction of losses
- Optimizing the systems
interactions
- Decoupling of systems
Up to 50%
Table 1 Fuel Efficiency improvement potentials
for a wheel loader
Site optimization
A work site set up is usually set by the capacity
where maximum capacity at worst conditions sets
type and size of machines to use, which results in
overcapacity most times. How to use the
overcapacity has a large impact on the fuel
efficiency. Also the work site layout has large impact
on fuel efficiency, to utilize the momentum in the
machine and have smooth turning radius close to
elevations. Maybe the biggest potential is minimizing
stock piles where all performed work is waist.
Looking at the total production on a work site there
are several possibilities to optimize the productivity
and fuel efficiency, see [1]. The potential lies in
using the correct machines for a given production or
work task, as well as in coordinating the different
machines to operate efficiently together logistically.
One example is to plan and control the operation of
machines to minimize queuing and waiting times on
the site. The improvement potential is highly
dependent on site and production but up to 30 %
have been identified.
Machine use optimization
Wheel Loaders are a versatile product and because
of that, the machine cannot be optimized for one
single application. The machines are often used in a
variety of working cycles and transporting various
materials.
Even if machine missions are planned and
controlled in a good way to maximize the total
productivity/efficiency on a site, the individual
machine operator has a high influence in the way he
or she manages to utilize the machine
productivity/efficiency capability. One study [2]
shows that efficiency varies up to 40% between
different operators assigned with the same task
using the same machine. The differences lies in for
example how traction force and bucket force are
balanced during bucket filling, how machine motion

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and bucket motion are coordinated by the operator
using levers and pedals, and in the end how these
tradeoffs make the machine systems like engine,
transmission, and hydraulics, work together.
Construction machines efficiency varies even among
experienced operators and requires good knowledge
of subsystem interaction in order to work efficiently.
Hence, there is a high potential for operator
assisting systems or even for complete autonomous
operation.
Machine optimization
The potentials for the machine optimization can be
grouped into three categories:
• Reduction of losses
• Optimizing the systems interactions
• Decoupling of systems
In the following, the optimization potentials in one
working cycles will be identified and 3 technical
solutions to capture these potentials are shown. In
all cases the driveline technology is the enabler to
capture the potentials.
REFERENCE WORKING CYCLES
Two working cycles are most relevant when
comparing efficiency in a wheel loader application:
Load & Carry and Short Loading Cycle Figure 1.
Figure 1 Short Loading Cycle
Description Short Loading Cycle:
1. Bucket filling
2. Leaving bank
3. Retardation for reversing
4. Reversing
5. Towards Load receiver
6. At load receiver
7. Leaving load receiver
8. Retardation for reversing
9. Towards bank
10. Retardation towards bank
Figure 2 Power distribution in a Short Loading
Cycle
Figure 2 shows the distribution of power - hydraulics
vs. drivetrain - in the short loading cycle. The x-axis
shows time and y-axis power in % of max. engine
power. The machine used is equipped with 4 speed
powershift transmission and torque converter (no
lock up). This graph is used as the baseline for all
potential evaluations.
Figure 3 Engine torque and speed plot TQ
powershift transmission
The phases are separated by white vertical lines
with the numbering as in above description. The
peak power demand is in the bucket filling phase,
where both, hydraulics and drivetrain, are
consuming up to the maximum engine power. This
phase is also relatively long in the cycle time, so that
40% of the total cycle fuel consumption happens in
this phase.

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Figure 3 shows a typical engine torque and speed
plot of the short loading cycle on the example of an
L 220 G.
MACHINE OPTIMIZATION: ENERGY
SAVING POTENTIALS IN WORKING
CYCLES
Optimization potentials in the working cycle
Three categories of optimization potentials were
stated above: Reduction of losses, optimizing the
systems interactions, Decoupling of systems.
Losses: There needs to be a continued focus to
minimize losses in every component, however the
biggest saving potential can be captured by
replacing big loss generating components with
different technologies. A torque converter generates
large losses, up to 25% of engine power in the
bucket filling phase and up to 20% of engine power
during travel (if w/o lockup). As the bucket filling
phase is contributing with 40% of the fuel
consumption in a short loading cycle, the reduction
of TQ losses in bucket filling is the single biggest
saving potential.
For the hydraulic system there is a large potential
during phases where no work is performed - tilting to
empty bucket, lowering boom. In these conditions
the hydraulic pumps are working against the
backpressure in the system. Of course there is room
for general efficiency improvement also in the
hydraulic system.
Optimizing system interactions: The biggest
potential in this category is the phlegmatization of
the engine power by energy storage. This means
that in phases of little power demand the energy
storage device is charged and that energy is used to
boost in high demand conditions. In the investigated
cycle the average power demand is only 60% of the
available peak power, however peak power is
needed for performance in certain conditions as
combined lifting in uphill conditions to feed a
crusher.
A very large factor for an efficient use of the
machine is the machine harmony, the balance of
hydraulics vs. propulsion system and the ease of
controlling the two. Achieving a good balance has a
large impact on the bucket filling ability, and hence
the productivity of the machine in real life.
Decoupling of systems: The individual system
elements of the machine (i.e. engine, hydraulics and
propulsion) have different best efficiency operating
points. The target for a machine configuration is to
match the components regarding their best
efficiency points for average working cycles. This is
always a compromise. Higher freedom in controlling
component operating points individually, will lead to
better overall machine efficiency. It is particularly
relevant to operate the engine in the sweet spots of
the fuel map (lowest BSFC). So fixed ratios or
limited flexibility of ratios between hydraulic flow and
engine rpm will lead to high engine rpm at relatively
low load and hence sub optimal fuel consumption for
the power demand. The same principle applies for
the propulsion system.
Technical approaches
With regards to machine optimization, Volvo CE has
investigated different technical solutions in a step
wise approach, while some solutions are launched
to the market, other solutions have been analyzed
with prototypes. Table 2 shows the Fuel Efficiency
improvement potentials by means of machine
optimization. It also shows the area of improvement
in the cycle and the technical approach to capture
the potentials.
Up to 15%:
• Retardation: using brakes instead of engine
• Reduction of losses: TQ lock-up functionality
Up to 25%:
• Reduction of losses: CVT instead of torque
converter
• Decoupling of engine speed and wheel speed
Up to 50%:
• Reduction of losses: CVT instead of torque
converter
• Decoupling of engine speed, wheel speed and
hydraulic flow
• Retardation and attachments: energy recovery
• Engine phlegmatization: downsizing and
boosting
Table 2 Machine optimization: Fuel Efficiency
improvement potentials and technical
approach.
In the following the technical solutions for the 3
steps are shown.
VOLVO OPTISHIFT
The Volvo Optishift feature has been introduced for
L110 – L 250 G-series models. The technical
solution consists of a lock-up torque converter and a
functionality that is referred to as “Reverse by
Braking (RBB)”. This functionality uses the wheel
brakes for the retardation of the machine during the

5. ICPC 2013 – 3.3
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powershuttle operation (phases 3 and 8 in the
driving cycle). Powershuttle is the automated shifting
from reverse to forward and vice versa by a push of
a button. Machines without this option use engine
power to slow the vehicle down and hence consume
fuel for this action.
Fuel efficiency improvements have been
demonstrated up to 15% while the RBB has the
biggest effect in the short loading cycle, the lock-up
functionality in load and carry and transport cycles.
Together with the introduction of the Optishift, the
gear shift quality was improved.
VOLVO HYDROSTATIC POWERSPLIT
CVT
The step up to 25% Fuel Efficiency improvement
has been demonstrated on a prototype wheel loader
equipped with a hydrostatic powersplit Continuously
Variable Transmission (CVT). Figure 4 shows the
patented gear scheme.
Figure 4 Volvo Hydrostatic Powersplit CVT
The CVT features individual yoke actuation of the
pump and the motor and is based on an output
coupled powersplit principle with 3 ranges.
A CVT uses the following potentials in the driving
cycle:
• elimination of torque converter losses
• decoupling of engine speed and wheel speed in
order to optimize the engine operating points
• reverse power flow during retardation to support
the engine for hydraulic power
Figure 5 shows the engine torque and speed plot of
the CVT wheel loader in the short loading cycle. It
can be see that engine speeds stay below 1400
rpm.
Figure 5 Engine torque and speed plot CVT
VOLVO SERIES ELECTRICAL HYBRID
The next step to capture further Fuel Efficiency
improvement potentials could be a series electrical
hybrid with energy storage and fully decoupled
hydraulics where every main function is decoupled.
Volvo has proven up to 50% improved FE with a
system architecture as shown in Figure 6.
The FE improvement potentials are based on the
following:
• Reduction of losses: el. CVT instead of torque
converter
• Retardation: energy recovery
• Engine phlegmatization: downsizing and
boosting
• Decoupling of engine speed, wheel speed and
hydraulic flow
The system features a downsized engine, an el.
Generator and 3 el. Motors for propulsion, and the
hydraulic functions lift and tilt. The Electric power
installed for the propulsion is: 70kW cont. / 120kW
peak. with PM synchronous el. Motors. The
transmission features 3 speeds, no F/R, no TQ and
a dry sump. The hydraulics features separated
circuits for lift/tilt and are pump controlled (throttle
free). The chosen voltage level is 600V and as

6. ICPC 2013 – 3.3
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energy storage device a supercapacitor with 400 Wh
capacity.
Figure 6 Components of Volvo Series El. Hybrid
Figure 7 Engine torque and speed plot Volvo
Series El. Hybrid
It can be seen in Figure 7 that the control strategy
avoides high fuel comsumption operating points in
the engine map and at very low rpm if the power is
not needed. In the series hybrid the engine becomes
a pure genset that delivers power. Also the hydraulic
pumps are disconnected from the engine, hence the
optimum engine operating point can be freely
chosen. Compared to that, the CVT solution
featured a fixed hydraulic mounting to the engine.
For the series hybrid setup the engine is controlled
to minimize losses for the total power delivering
system, i.e. engine, generator, and energy storage
together. This is a balance that for any given power
demand compromises between engine/generator
losses and energy storage losses, see [3] and [4].
Figure 7 shows engine operating points for a short
loading cycle. For such cycles the energy storage
can deliver power to cover for peak demands. That
is the reason why the engine is never operated at
more than about two thirds of its power capability.
The used engine has been dimensioned for an
infinitely long uphill transport, about 84kW are
required for this usage in this machine. Since the
uphill slope is infinitely long, the generator power
cannot be topped by the energy storage. Therefore
both engine and generator are sized for that
operating condition.
CONCLUSIONS - ADDING VALUE
Three possible technical routes have been shown to
capture potentials for Fuel Efficiency improvements
in the wheel loader application. There is substantial
potential - up to 50% improvement - if the machine is
optimized by introducing new technologies. New
technologies however tend to come with a cost tag!
For the machine owner the cost per ton of moved
material counts. So productivity and the total cost of
ownership (TCO) are the influencing factors. The
cost for fuel in the TCO (10 years) is in the range of
20% for wheel loaders in the class > 15t in Europe
(with operator). The purchase price is in the range of
20%. There are various customer groups of course
with different buying criteria. A rule of thumb can be
applied, that customers’ requests an ROI < 2 years,
which leads to basic question: how much technology
can the customer afford to buy? Different than in the
car industry or industries with public exposure (i.e.
city busses), the construction equipment industry
cannot count on any image driven purchase
decisions - money counts.
There is an opportunity however to provide
additional features and added value with a new
technology, for example increased durability due to
reduced number of parts, improved ease of
operation, new features aso.
The next challenge is the financial view of the
machine OEM: there are of course targets on
machine margin, ROI for development projects and
amount of invest. Shareholders are asking for added
value.
OEMs are different, in terms of manufacturing depth,
customer groups and applications, global sales

7. ICPC 2013 – 3.3
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footprint, industrial footprint, supplier base and
synergies within the group. The current competitive
landscape shows that various technical solutions are
launched to the market and that the diversity of
technical solutions in the market grows. Market
launches include CVT and hybrid solutions on a
hydraulic and electrical base.
Every OEM needs to define its way to add value to
customers and shareholders, there is no “silver
bullet”. Those OEMs which develop and produce all
major components of a machine, benefit form much
larger optimization potential and technical choice
though.
OUTLOOK
After discussing options for the short and midterm
future, how can the far future look like? There are
industry trends that can lead to very different
machines and business models of selling
construction equipment.
To list a few opportunities:
Electrification of job sites
Especially in mines and quarries, the electrification
of job sites has come quite far. For mining and
underground equipment full electric machines are
reality. The cost for electric energy (if energy is
supplied from a grid) is significantly lower than diesel
when taking into account the low efficiency of
combustion engines vs. electric power generation.
There is a clear potential for a technology shift.
Battery cost
Once battery technology matures and is reduced in
cost, there is a potential to reroute value streams
from fuel suppliers to OEMs. The cost for the battery
will be overcompensated by the fuel savings. If the
battery is supplied via the OEM, there is a clear
business growth opportunity.
Alternative fuels
Natural gas is seen as a potential to take some of
the share of diesel fuel. Depending on the cost
development, this can have an influence on the
speed of change of machine technology.
Vehicle concepts
There is an opportunity to “think out of the box” and
come with radically new machine concepts. The
Volvo Gryphin is an example with new ideas and
added features for the machine usage.
Features:
• Electric hybrid with energy storage
• Electric wheel motors
• Independent wheel suspension
• Electrohydraulic actuators
• Extendable counterweight
• Energy regeneration from drive and attachments
• Diversified energy carrier
• Fuel cell power source potential
Figure 8 Volvo Gryphin – wheel loader future
concept
REFERENCES
[1] “Microsimulation of total cost of ownership in
quarries”. Erik Uhlin
[2] “On increasing fuel efficiency by operator
assistant systems in a wheel loader”. Bobbie
Frank, Lennart Skogh, Reno Filla, Anders
Fröberg, and Mats Alaküla1. The 2012
International Conference on Advanced
Vehicle Technologies and Integration.
[3] “Optimal transient control of power generation
in hybrid construction equipment”, Anders
Fröberg, Jan Åslund, and Lars Nielsen, IEEE
Vehicle power and propulsion conference,
2011.
[4] “Estimation of fuel equivalence factor from a
wheel loaders driving cycle”. Peter Nyberg
and Anders Fröberg. The 2012 International
Conference on Advanced Vehicle
Technologies and Integration.
[5] “Hybrid Power Systems for Construction
Machinery: Aspects of System Design and
Operability of Wheel Loaders,” Reno Filla.
ASME Technical Paper IMECE2009-10458,
2009, doi: 10.1115/IMECE2009-10458.
[6] “Alternative system solutions for wheel
loaders and other construction equipment”.
Reno Filla. (2008) 1st International CTI Forum
Alternative and Hybrid Drive Trains, Berlin,
Germany.

8. ICPC 2013 – 3.3
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http://urn.kb.se/resolve?urn=urn:nbn:se:liu:div
a-43948
[7] “Quantifying Operability of Working
Machines,” Reno Filla. Ph.D. thesis,
Department of Management and Engineering,
Linköping University, Linköping, 2011.
http://urn.kb.se/resolve?urn=urn:nbn:se:liu:div
a-70394
DEFINITIONS, ACRONYMS,
ABBREVIATIONS
FC Fuel consumption
FE Fuel Efficiency
TQ Torque converter
CVT Continuously Variable Transmission
RBB Reverse by Braking
TCO Total Cost of Ownership
BSFC Brake Specific Fuel Consumption
OEM Original Equipment Manufacturer