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B1( Lee Grant
A
fter the oil embargo of 1973-74 and
the ensuing energy crisis, Congress
passed the Energy Policy and
Conservation Act, which established the
Corporate Average Fuel Economy (CAFE)
standards for new passenger cars and
light trucks. The initial standards were set
at 18 miles per gallon (mpg) for passenger
cars and 17.2 and 15.8 mpg for two-wheel
and four-wheel drive light trucks, respectively. Both standards have been
increased gradually to the cu rrent stand ards of 27.5 mpg for cars and 20.7 mpg
for light trucks.
To ensure compliance with CAFE, the
u.s. Environmental Protection Agency
16
(EPA) computes an overall average fuel
economy for each manufacturer each
model year. Manufacturers take fuel economy measurements for each vehicle type
at the same time EPA is determining emissions compliance for that vehicle. The
numbers of each vehicle type sold
weights the overall CAFE fuel economy
compliance figures. If a m anufacturer
does not meet the stand ard, it is liable for
a civil penalty of $5 for each 0.1 mpg its
fleet falls below the standard, multiplied
by the number of vehicles it produces.
On March 13, 2002, the u.s. Senate
defeated an effort to increase fuel economy standards by 50 percent over the
Technology Today. Fall 2002
next 13 years for cars, light trucks, minivans
and sport utility vehicles. Had it passed, the
measure would have provided the first
increase in the standards for passenger cars
since 1986, and since 1996 for light trucks.
Since the inception of CAFE standards in
1978, the fuel economy of the nation' s new
car and truck fleet has increased by more
than 20 percent. However, improvements in
fuel economy peaked during the model
years of 1987-88. With the rise in popularity
of minivans and SUVs the fuel economy of
the nation's fleet has since decreased some
7 percent. This decrease in fuel economy
prompted the most recent congressional
review of the standard.
c
From left, Michael A. Kluger of the Engine and Vehicle Research Division and Steven D.
Marty, Lee J. Grant and Larry A. Eckhardt of the Automotive Products and Emissions
Research Division, are among the Institute's experts on procedures designed to evaluate
fuel economy and the design of equipment and procedures to do so. Their specialties
include fuel effects on emissions, fuel evaluation and performance, engine research ,
engine test development, automotive fluids analysis and fleet analysis.
The model year 1987 fleet, including
both domestic and imported passenger
cars and light trucks, had a CAFE of 26.2
mpg, a whopping 30 percent increase over
1979 averages. In the late 1980s, in a move
Congress didn't anticipate in 1975,
automakers began to phase out most fullsize cars and station wagons as consumers began the switch to light trucks, a
category that in cludes pickups, minivans
and sport utility vehicles. When Congress
enacted the original standards, light
trucks comprised less than 10 percent of
the new-vehicle market.
Today, after a decade of low fuel
prices and the public's continued love
affair with size and horsepower, half of all
new vehicles sold are pickups (20.5 mpg
average); minivans (22.5 mpg average);
and SUVs (20 mpg average).
American consumers have trad ed
fuel economy for acceleration and weight,
and consequently the average fuel econom y has slipped to 24 mpg.
Participating in autom otive research
fo r more than 50 years, the Institute's
Automotive Products and Emissions
Research Division and Engine and Vehicle
Research Division h ave long been
involved with clients seeking an independ ent site to evaluate technologies for
incremental fu el economy improvements.
Beginning in the 1970s, automotive
manufacturers made huge gains just by
tackling the aerodynamics of design and
the weight of their vehicles. Since then,
gains in fuel economy have been smaller
and tougher to com e by. For many years,
SwRI has offered industry-standard and
Technology Today ' Fall 2002
proprietary test p rocedures with which to
validate these minute improvem ents.
Vehicle and oil testing procedures
The Institute follows the same EPA
test procedure to m easu re fuel economy
that it u ses to m easure light-vehicle
emissions. SwRI engineers test vehicles
by driving them on a chassis
dynam om eter u nd er laboratory conditions. One cycle simulates the slower
sp eed s, stop s, idling, and accelerations
of stop-and-go driving. The other cycle
simulates a lO-mile highway trip w ith
little idling an d one stop before the end
of test. Fuel consu m ption numbers are
combined to compute fuel econom y.
Though CAFE does not extend to
heavy- duty vehicles, fuel economy is
nevertheless a high priority fo r m anufacturers and fleet operators. SwRI engineers
often use a Society of Autom oti ve
17
DE 139247
Engineers fuel consumption test to
evaluate fuel economy benefits
associated with fuel additives,
engine oil and driveline lubricant
formulations, as well as tires and
other fuel-saving devices.
Technicians drive trucks and
buses on a prescribed minimum
40-mile "course" to simulate a
long-haul route. During this procedure, engineers compare the inservice fuel consumption of a
control truck to one to three test
trucks. SAE introduced this test
method in 1986, and experience
shows that it has an overall accuracy of plus or minus 1 percent.
SwRI also uses several other
SAE test procedures to establish
relative fuel economies of components and systems. For example,
the fuel economy measurement
road test procedure provides fuel
economy measurement techniques
for light-duty vehicle components.
This test can be performed on the
road or on a chassis dynamometer
and, like the EPA procedure, it
simulates a mix of city, suburban
and highway driving conditions.
In another effort to improve
fuel economy, automakers and oil
and additive suppliers have
demonstrated the benefits of
energy-conserving, low-viscosity, multigrade engine oils. To qualify such oils for
the marketplace, SwRI engineers use the
Sequence VIB test, which measures the
effects of engine oils on the fuel economy
of light-duty vehicles and the ability of
the oil to retain its fuel economy benefits
30
The axle efficiency test stand
is used to evaluate different
types of axles or oils for their
fuel efficiency benefits.
Additional research
over an entire oil change interval. SwRI
performs a similar procedure, the
Mercedes-Benz M-l11 Fuel Economy Test,
on an engine dynamometer test stand that
simulates the European emissions test
procedure. SwRI still uses a 1982 forerunner of the Sequence VI test for research
purposes in evaluating
fuels, engine oils, gear
Fuel Economy by Model Year
oils and automatic transAverage MPG
mission fluids.
In this procedure,
_____
Cars
engineers drive five cars
through varied driving
Both
cycles on the chassis
dynamometer to demon____________________________ _Tr!l~k.s
strate differences in fuel
economy.
~----
25
20
According to a 2001 EPA study,
only about 15 percent of the
energy content of the gasoline
in a vehicle's tank actually
moves the car down the road.
About two-thirds of the available energy in the fuel is
rejected as heat in the exhaust
and coolant or frictional losses.
Energy is lost to engine friction, pumping losses, drivetrain
friction and slippage, the operation of accessories such as airconditioning, aerodynamic
drag, tire rolling resistance and
idling in traffic. Each of these
losses is an opportunity for
advanced technology to
improve fuel economy.
Researchers often measure
motoring friction to determine
the effects of any device on engine friction and to map engines and calculate
fuel consumption while looking at the
effects of different components, front-end
accessory devices, fuel-enhancement
devices and fuel additives. Because air
filters can affect fuel economy, SwRI has
a procedure to measure the dust capacity
of a filter to determine its load before
there is a drop in air pressure. With the
goal of finding an additional fraction of a
mile per gallon, SwRI has developed
benchmarking programs for auto manufacturers in which engines, transmissions, pumps and accessories of clients
are evaluated.
SwRI design engineers playa major
role in helping their clients reduce engine
15
10+-~~~~~++~r+~~~~~~~~r+~~~~+
1970
1975
1980
1985
1990
Model Year
1995
2000
Source:
Fuel economy for US. vehicles peaked in the mid 1980s and
has since declined with the popularity of less fuel-efficient
vehicles such as the SUV
u.s. EPA
D010445
18
Technology Today • Fall 2002
A road or chassis dynamometer,
which simulates on-road vehicle
use, helps to measure the
energy efficiency of a
lubricant, fuel, or component. It
can also be used to optimize the
axle components and the
assembly of the components.
friction through component
design and the use of
advanced materials.
Combustion modeling has
been used to develop intake
systems with improved
combustion, and advanced
engine controls have contributed to improved coldstart fuel consumption.
Two drivetrain components that
auto and component manufacturers often
ask SwRI sfaff to evaluate are the drive
axle and the transmission. Axle efficiency
improvements smaller than 1 percent can
be significant for fuel economy.
SwRI uses several published and
proprietary procedures to evaluate axle
hardware and shaft speeds and to log
data as the load is increased linearly to
some elevated load. SwRI technicians
repeat this procedure at many different
speeds and temperatures.
Similar to the trend in engine oils,
automatic transmission fluids are evaluated for viscometries and friction properties. Maintenance of friction
properties is necessary for the proper
operation of the slipping torque converter, itself a major contributor to overall transmission efficiency
improvement. Lower viscosity transmission fluids reduce the drag within
the transmission to improve performance, particularly at lower
temperatures.
The Institute has become a worldclass transmission test facility for studying transmission performance,
transmission fluid performance and
component efficiencies.
Transmissions operate over such a
wide range of power conditions that
their efficiencies can vary from 65 to 95
percent. Components are isolated outside the transmission to study their singular contribution to efficiency losses.
Conclusion
Despite the Senate's March 13 vote
to block an increase in CAFE standards
for cars and light-duty trucks, greater fuel
economy will remain a high priority in
the automotive industry. Crude oil is still
a finite resource, and light vehicles
account for about 40 percent of all U.S. oil
consumption. Other nations, as well as
environmental groups, will continue to
pressure the President and Congress to
address global warming. Major automakers have started to compete on environmental issues. For example, Ford has
announced plans to increase the fuel
economy of its SUVs by 25 percent by
2005, and General Motors has pledged to
remain the fuel economy leader in light
trucks. Through continuous development
of industry and proprietary procedures,
SwRI will retain its leadership role in
assisting manufacturers and fleet operators with lower emissions and improvements in fuel economy. .:.
Comments about this article? Contact Grant
at (210) 522-5004 or lee.grant@swri.org.
A clutch pack drag test stand is used to
measure the parasitic losses associated
with different transmission clutch pack
variables such as friction material
groove design, oil flow, relative component speeds and axial clearance.
Teclmology Today. Fall 2002
19