THE UTEP “HEADHUNTER” E85 CHEVROLET SILVERADO
A. Hutchison, O. Acosta, J. Carrillo, J. Guerra, F. Jasso*, L. Martinez, A. Medina, F. Medina,
O. Moguel, J. Perez, M. Perez, O. Rodriguez, L. Terrazas, G. Villa, R.B. Wicker**
The University of Texas at El Paso Department of Mechanical and Industrial Engineering
El Paso, Texas 79968-0521
*Team Captain
**Faculty Advisor
ABSTRACT
operation according to the competition rules [1]. The
University of Texas at El Paso (UTEP) team consists of
fourteen student team members working within the
Engines & Alternative Fuels Research Laboratory
(EAFRL). The EAFRL occupies approximately 2,500
square feet of floor space within the Mechanical and
Industrial Engineering Department and has research
equipment that includes an engine test cell and engine
dynamometer, flow rate measurement bench, chassis
dynamometer,
continuous
emissions
monitoring
equipment, cold start test facility, and various additional
equipment. The interested reader is encouraged to visit
our web site at www.me.utep.edu/research/afrl to view
EAFRL related activities and facilities.
The University of Texas at El Paso (UTEP) has
developed a dedicated E85-fueled Chevrolet Silverado
pickup with superior emissions, cold starting, and
performance when compared to the original gasolinefueled vehicle. All fuel system components not E85
compatible have been replaced or modified. Ethanolspecific light-off and main catalysts are utilized for
emissions reductions, and an experimentally optimized
air injection system rapidly heats the catalysts for
reduced cold start emissions. Emissions tests have
been performed at an EPA certified emissions test
facility. Cold starting characteristics are improved by
incorporating a high energy multiple spark ignition
system, successfully extending the lean flammability limit
of E85. Cold start testing has been performed within a
cold start test facility and an experimental procedure has
been developed to determine engine start time. There
have been no internal engine modifications to maintain
fuel flexibility. However, an on-demand strategy utilizing
a centrifugal supercharger at high load provides
increased performance.
Baseline and modified
performance measurements have been made using an
engine dynamometer. Certain engine control data within
the Engine Control Module (ECM) have been modified
based on experimentation, although the majority of the
stock gasoline control strategy has been retained. To
account for differences in fuel characteristics, increased
mass flow rate fuel injectors are used. Individual fuel
injectors have been calibrated using a newly developed
fuel injector testing system, and each injector selected
for the conversion provides fuel flow within a specified
tolerance. The complete UTEP Challenge experience
includes a substantial sponsorship effort, a student
developed web page, and an attractive, functional, and
consumer acceptable Chevrolet Silverado pickup.
UTEP has participated in a number of Department of
Energy-sponsored vehicle challenges including the 1993
CNG Vehicle Challenge, the 1995 Hybrid Electric
Vehicle Challenge, the 1996 and 1997 Propane Vehicle
Challenges, and now the 1998 and 1999 EVCs.
Numerous educational benefits are derived from
participation in these challenges. This year’s team is
composed of undergraduate and graduate researchers
within the EAFRL, three senior design project teams
(with two students each), and several student
volunteers. Examples of some of this year’s educational
accomplishments include the design and development of
an engine cold start test facility with an automated test
procedure, a fuel injector test stand, an air injection
system, and an on-demand performance enhancement
strategy. The UTEP team has also performed extensive
engine dynamometer and cold start testing.
As stated in the 1999 Ethanol Vehicle Challenge
Competition Rules and Regulations [1], the EVC is
intended to advance the development of optimized,
dedicated, E85-powered vehicles, specifically in terms of
vehicle performance, emissions control, fuel economy,
and cold starting. In addition, the Challenge is intended
to collect data to define the state of E85 vehicle
technology, and to provide student engineers with a
valuable hands-on learning experience in a real-life
interdisciplinary engineering project. The UTEP team
has addressed all of these aspects of the Challenge as
well as several others.
INTRODUCTION
The 1999 Ethanol Vehicle Challenge (EVC) involves
fourteen schools from across the United States and
Canada. This represents the second year for E85 (85%
denatured ethanol and 15% gasoline) as the motor fuel
sponsored by the Department of Energy Alternative Fuel
Challenge series. The challenge for the teams is to
convert a 1999 Chevrolet Silverado with a General
Motors (GM) Gen III 5.3L V8 engine to dedicated E85
The UTEP strategy has always been to combine
simplicity and sound engineering practices with the
1
APPEARANCE AND COMPETITION SUPPORT
effective use of experimentation for design validation.
Using this principle, the UTEP team focused on five
basic technical areas for the 1999 challenge. These
areas are briefly described below.
In addition to the technical aspects of the competition,
UTEP has also focussed on vehicle appearance, team
sponsorship, and establishing a web page. In order to
improve vehicle appearance, a custom paint scheme
has been applied to the truck. The truck has been
painted in the school colors of white, orange, and blue,
as seen in Figure 1. Using Volatile Organic Compound
(VOC) compliant paint, a pattern has been selected
which not only depicts school spirit, but it also amplifies
the truck design. The truck surface has been painted
using high-quality White Diamond and Dark Cloisonne
Poly (Blue) base colors, with a design marked out and
painted with Pearl Orange. To seal the paint, a Clear
Coat of 2001 DBC clear has been applied.
1. Fuel System Compatibility: Fuel system components
not ethanol compatible have been replaced or
modified.
2. Cold Start Strategy: A multiple spark ignition system
is utilized to extend the lean flammability limit of E85.
In addition, an automated cold start testing
procedure has been developed for accurate cold
start test times.
3. Engine Management: The original GM ECM is used
along with some modifications provided by GM and
outlined in the 1999 Ethanol Vehicle Challenge
Calibration Guide [9].
To further add to the truck appearance and safety,
several other options will be added to the truck. A local
company has donated a brush guard, nerf bars, and
custom horn. For safety, the truck is equipped with a 5
lb. ABC type fire extinguisher and CB radio.
4. Emissions: A dual air-injection system is utilized to
minimize cold start emissions and rapidly heat the
exhaust catalysts. Ethanol-specific light-off and
main catalysts have been placed in the exhaust
system. Fuel injector characterization testing has
been performed on every injector in order to
minimize potential cylinder-to-cylinder fueling
variations.
Sponsorship activities make up a fairly large part of the
UTEP commitment to the Challenge. Students make
initial contact with a potential sponsor and provide them
with a sponsorship packet including a description of the
Challenge, UTEP’s strategy, and several photos of past
and present Challenges. The students then arrange to
give a sponsorship presentation at the sponsor’s
business location. After receipt of a donation, the
students follow up with a thank you letter and an official
sponsor poster (one of the sponsor posters is shown in
Figure 2). To date, this effort has resulted in excess of
$30k in industry support ($20k in financial donations and
more than $10k in hardware donations). In addition to
improving communication skills, this process has
provided a positive avenue for improving the image of
our University.
5. Performance: There have been no internal engine
modifications to maintain fuel flexibility. However, an
on-demand
strategy
utilizing
a
centrifugal
supercharger at high load provides increased
performance. The on-demand strategy restricts the
performance enhancements to wide open throttle
(WOT) operation, thus allowing emissions and fuel
consumption to be optimized at part load operation.
A novel intake system that utilizes ambient air over
all driving conditions except WOT has been
designed.
Finally, UTEP has developed a web page that highlights
the EAFRL activities including past and present
Challenges. The interested reader should check out
www.me.utep.edu/research/afrl to see a remarkable web
page with all graphics created by Challenge students.
Several components and systems are critical to the
success of the conversion and operation of the 1999
UTEP truck.
Our new cold start facility, engine
dynamometer, and fuel-injector test rig provided the
team with invaluable data, which is necessary for a
successful conversion. A multiple-spark ignition system
and air injection system are key to the strategy of the
1999 UTEP team.
The following more fully describes the five technical
areas addressed by the UTEP team. However, the
complete UTEP Challenge experience has included a
substantial sponsorship effort, a student developed web
page, and an attractive, functional, and consumer
acceptable Chevrolet Silverado pickup. These areas will
be briefly discussed first.
Figure 1 – The 1999 UTEP EVC truck.
2
FUEL SYSTEM COMPATIBILITY
Due to the nature of ethanol, the fuel system must be
free of any aluminum components. Since aluminum is
desirable in automotive applications because of its high
strength to weight ratio, many components in the fuel
system had to be replaced.
Figure 3 shows the converted fuel rail assembly. Some
internal components in the fuel rail had to be replaced,
such as inside and outside fuel caps. As can be seen in
the figure, the caps have been remanufactured with
stainless steel. The fuel rail assembly has also been
modified so that a replacement fuel pressure regulator
can be installed.
GM provided the EVC teams with an E85 compatible
fuel pump. To regulate the fuel pressure, a Paxton 8001690 fuel pressure regulator has been installed on the
fuel rail assembly. This pressure regulator can regulate
pressures from 0 to ~100 psi (690 kPa) with our
configuration. A MSD alcohol-compatible high-pressure
in-line fuel filter has been installed. Stock O-rings have
been replaced with Nitrile No. 36 O-rings, which maintain
their structure while in contact with ethanol.
Figure 2 – An example of a sponsor poster.
COLD START STRATEGY
In accordance with the strategy used by Crane, et.al. [3],
the UTEP cold start strategy is composed of three parts.
First, excess fuel is injected into the cylinder at start-up.
In order to reduce ignition time, the lean flammability
limit of E85 is extended with a multiple-spark ignition
system. Finally, as is described in the emissions section
below, an air injection system is introduced in the
exhaust to rapidly oxidize the excess CO and HC
emissions on cold-start. In order to compliment the
above strategy, a procedure for measuring cold start
time has been developed in order to optimize our cold
start strategy.
At this time, the final specifications of certain fuel system
components are not known. The flame arrestor design
has not been finalized. However, the flame arrestor will
be constructed of a stainless steel fitting with a wire
mesh. The fuel injectors are another component that
must be replaced with E85 compatible versions. GM
provided the teams with E85 compatible fuel injectors
from Delphi. However, higher-flow E85 injectors have
also been obtained from Delphi. Results of cold start
and performance tests will determine which set of
injectors will be used.
Figure 3 – E85 compatible fuel rail, end caps, and adjustable pressure regulator.
3
Figure 4 – Cold start room diagram.
angle before every test. The signal from the pressure
sensor is sent to an amplifier, and then to the data
acquisition card. Thermocouples are used in several
locations, such as to measure exhaust gas, ambient,
and oil temperatures. Programs written in LabVIEW are
then used to collect and plot the data.
COLD START TEST FACILITY
As part of the cold start strategy, a method of
determining engine start up time under simulated coldstart conditions has been developed. This method
includes automating the cold start facility, taking incylinder pressure and temperature measurements, and
collecting data with a data acquisition card connected to
a computer.
A typical procedure for conducting a cold-start test is as
follows:
The cold start setup, as can be seen in figures 4 and 5,
involves many areas of data acquisition and
measurements. An engine is placed inside the cold start
facility where the temperature can be reduced to as low
as -4 oF (-20 °C).
In order to acquire pressure
measurements, a Kistler measuring spark plug with
integrated cylinder pressure sensor is placed in one
cylinder. In order to achieve consistency in the data
measurements, the engine is placed at the same crank
Figure 5 – The EAFRL cold start facility.
4
•
Set crank angle to pre-set position. An indicator
placed on the engine is used to reset to the same
angle before every test.
•
Set the desired temperature in the cold start facility.
Generally, since cold tests are desired, this
temperature may vary from anywhere between -4 to
+32oF (-20 to 0 °C).
•
Allow engine and all of its components to cool to a
uniform ambient temperature.
•
On the control panel, switch on the power and fuel
pump and prepare for crank.
•
Push starter button, which in turn triggers the data
acquisition on the PC.
•
Once engine is running, release starter button and
review pressure data.
•
Determine time measurement.
CD ignitions produce quick, high-intensity sparks that
are very effective at igniting the in-cylinder fuel air
mixture. Because of the rapid charging and discharging
capability of the CD system, multiple sparks can be
generated within the duration of the power stroke. The
prototype MSI system effectively combines these two
systems, providing one long-duration spark, with multiple
“hot spots,” or high-energy pulses, within the spark.
Figure 6 shows the layout of the MSI system, and the
integration into the stock ignition system. Because of
the ignition component integration on the GM Gen III
engine, two sets of coils are necessary for the system.
The output of the stock coil is routed through the MSD
coil, which triggers the MSI controller.
The MSI
controller sends a signal to the MSD coil, and the output
of both coils are then sent to the spark plug. Output
energy of the multiple-spark system is approximately the
same as the stock system, 100 mJ. However, the
addition of the MSI system results in the addition of
several peaks of energy into the spark. At low engine
speeds, such as during start-up, the MSI system will be
able to provide four high-energy pulses within the
duration of the HEI spark.
This procedure is followed to determine the engine start
time. Once the start time is determined, strategies can
be used to reduce the start time.
MSD IGNITION
The 1999 UTEP team is part of a development team with
Autotronic Controls Corporation, manufacturers of MSD
ignitions, in developing a multiple spark ignition (MSI)
system. The prototype MSI system is the centerpiece of
UTEP’s 1999 cold start strategy, with benefits gained in
the areas of cold start emission control and cold starting
performance. Because of the integration of the coil and
ignition driver in the GM Gen III engine, the original
ignition system in the truck could not be replaced with a
standard MSI system. Therefore, a “piggyback” system
combining the stock and MSI system has been
developed by Autotronic Controls and tested by the
UTEP team.
Based on data by Bae and Lee for gasoline [2], this
prototype MSI system should also benefit a dedicated
E85 package. This ignition system, with its high-energy
pulses, successfully extends the lean flammability limit of
E85 [2] to provide superior cold starting characteristics.
This system is similar to the 1998 cold start strategy, in
which UTEP performed very well [10].
COLD START RESULTS
In this system, the stock High-Energy Ignition (HEI)
system has been retained while adding a highperformance Capacitive Discharge (CD) ignition system.
The benefits of such a layout are many. HEI ignitions
produce a longer duration spark, which is beneficial for
complete combustion of the in-cylinder fuel air mixture.
The EVC team is currently optimizing our cold start
strategy. However, several modifications have been
performed on the ECM module, in order to benefit cold
start performance.
These modifications will be
described in the engine management section below.
Figure 6 – The MSD system mounted on engine and shown in simplified form.
5
Injector Fuel Primes
0.6
0.7
0.5
0.6
0.4
0.5
0.4
equivalence ratio
0.8
grams
Stock Prime Pulse Mass
(g)
Modified Prime Pulse
Mass (g)
Stock First and Second
Pulse Mass (g)
Modified First and Second
Pulse Mass (g)
Intake Air Temperature Enrichment
0.3
Stock Initial IAT
Enrichment
Modified Initial IAT
Enrichment
0.3
0.2
0.1
0.2
0
-50 -40 -30 -20 -10 0
0.1
10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
-0.1
0
-50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
-0.2
Engine Coolant Temperature (C)
Intake Air Temperature (C)
Figure 7 – Fuel prime map adjustments.
Figure 8 – Intake air enrichment adjustments.
to the ECM calibrations, additional fuel can be injected
into the cylinders by adjusting the fuel system pressure.
However, these changes do not affect cold-start
emissions, due to the UTEP emissions strategy.
ENGINE MANAGEMENT
The 1999 Ethanol Vehicle Challenge provided an
exciting opportunity to modify the GM engine control
module (ECM) with custom settings. The UTEP EVC
team took advantage of this opportunity by altering the
fuel prime and intake air enrichment maps to improve
cold starting performance. As was discussed in the cold
start section above, and the emissions section below,
these maps were adjusted based on cold-room testing
performed on the research engine. Figure 7 shows the
adjustment on the fuel prime map, and Figure 8 shows
the adjustment on the intake airflow enrichment map.
From the calibration guide [9], it was found that cold-start
prime was given in three stages. Fuel is injected into all
eight cylinders at key-on, at 45° crank rotation, and at
135° crank rotation.
EMISSIONS
The emissions strategy for the 1999 EVC is comprised
of two components, the use of ethanol-specific catalysts,
and the implementation of an air injection system in the
exhaust manifold.
These two strategies will be
described in the following sections.
AIR INJECTION SYSTEM
The use of secondary air injection is currently under
research as a means to decrease the time for the
catalytic converters to light-off, which is the temperature
at which 50% of exhaust emissions can be effectively
converted.
If air is introduced into a fuel-rich
environment, such as the one present in the exhaust
manifold during a cold start, the high concentrations of
hydrocarbons and carbon monoxide can be oxidized and
We are still optimizing our strategy for best cold start
performance. Currently, these changes provide almost
twice as much fuel to the cylinder at start-up. In addition
CHECK
VALVE
600
AIR
PUMP
400
o
Temp ( C)
500
EXHAUST
MANIFOLD
MULTIPORT
AIR
INJECTION
300
200
Baseline
with air
100
CATALYTIC
CONVERTER
0
0
100
200
300
400
500
600
700
Time (sec)
Figure 10 – Results of air injection system.
Figure 9 – Layout of the air injection system.
6
800
900
fuel pressure
gage
fuel
injector
power
supply
pressure
regulator
graduated
cylinder
fuel
scale tank
rel
ay
circuit
board
pump
pulse
generator
Figure 11 – Fuel injector test stand schematic.
Figure 12 – Photograph of fuel injector test stand.
converted into harmless derivatives, such as carbon
dioxide and water [3]. As a result of this chemical
conversion, there is a release of heat from this reaction.
By taking advantage of the heat released, a catalytic
converter can be rapidly heated by mounting it in close
proximity to the exhaust manifold.
exhaust manifold. The effectiveness of the air injection
system at warming up the catalysts is shown in Figure
10, which is under no load operation. Currently, tests
are being performed which simulate the FTP driving
schedule. Using a campus parking lot, the truck is
started and allowed to idle for 20 s, and then accelerated
to 25 mph. Measurements are then taken to determine
the effectiveness of the air injection system.
An iterative approach is being followed in the
development of an effective reduction system. Various
configurations have been tested, with the goal being
attaining the highest exhaust temperature possible.
After several test configurations, a multiport injection
strategy has been finalized upon. The multiport injection
places air injectors at different points in the exhaust
system. In order to maximize mixture of the air and
exhaust gases, the air injectors are placed as close to
the exhaust ports as possible. Currently, the team is still
optimizing the air injection system for use with ethanol.
ETHANOL-COMPATIBLE CATALYST
For exhaust emissions reduction, the stock ECM control
system has been combined with ethanol-specific light-off
and main catalysts from Allied Signal Environmental
Catalysts. The light-off and main catalysts are combined
in a single canister that was canned by Delphi. Ethanolspecific catalytic converters have been utilized to help
reduce the emission of aldehydes, and specifically
acetaldehyde, characteristic of alcohol fuels [4]. The
palladium light-off catalyst occupied the first third of the
can while the main catalyst occupied the remaining two
thirds of the can. Care has been taken to minimize the
light-off time for reduced cold start emissions of ethanol
by using the air injection system described above.
Figure 9 details the layout of a multiport air injection
system. As opposed to the stock configuration in the
California emissions package, the UTEP conversion
consists of placing injector ports at all cylinders in the
Comparison of 3 different fuel injectors at 60 PSI
45
40
Flow Rate (mg/pulse)
35
30
FUEL INJECTOR TEST STAND
y = 4.3429x - 1.0547
R2 = 1
gas injector
hi flow injector
super flow injector
Linear (gas injector)
Linear (hi flow injector)
Linear (super flow injector)
For this year’s competition, a fuel injector test stand has
been utilized in order to compare the performance and
output of each injector used in the competition. The
output of each injector must be equal so that power and
emissions will not be affected by a rich or lean condition
in one cylinder. Since even a small variation in injector
output would affect a change in cylinder stoichiometry,
every injector was tested despite strict tolerances in the
manufacturing process.
y = 3.6294x - 1.1369
R2 = 0.9999
25
20
y = 2.6458x - 0.6139
R2 = 0.9999
15
10
5
0
0
2
4
6
8
10
A schematic and photograph of the fuel injector testing
system are shown in Figures 11 and 12. On the right
side of this figure, the path of the test fluid from the fuel
12
Pulse Width(ms)
Figure 13 – Comparison of the linear range of 3 sets
of injectors.
7
EMISSION TESTS
tank to the injector can be seen. Wiring connections are
shown on the other half of the diagram.
A baseline FTP test has been performed at Southwest
Research Institute in February of 1999. This baseline
test consisted of a full 3-bag FTP-75 performed on the
stock gasoline fuel system, and without the air injection
system. The results of this test can be seen in Figure
14. Another FTP test will be performed in early May of
1999, where the results will be compared to the baseline
test. This second FTP test will prove the benefits of
ethanol and of UTEP’s emissions strategy.
An injector driver circuit has been constructed with a
high-frequency relay and a digital pulse generator. The
user can select a delay time and pulse width with the
pulse generator. In order to simulate various operating
conditions, a pressure regulator with fuel pump
adjustable from 0 to 100 psi ( 0 to 690 kPa ) is
connected to the fuel supply.
After the test is run for a particular pulse width, the fluid
mass is recorded and plots of dynamic flow versus pulse
width are created. The amount of fuel injected is
proportional to the time the fuel injector valve is open.
This is true since the pressure and geometry of the
nozzle remain constant. The testing system verifies this
injector characteristic with a proportional relationship
between the flow of the injector and the pulse width.
PERFORMANCE
An important aspect of a conversion to dedicated E85 is
the maintenance of the gasoline performance standard.
In order for alternative fuel vehicles to become
commercially successful, consumer appeal of these
vehicles must be maintained. Therefore, it is critical that
there be no losses in vehicle performance.
Three types of injectors have been tested and compared
to select the optimal injector.
The two injectors
designated by high flow and super flow are ethanolcompatible. The injectors were tested with a period of
0.1 second for pulse widths ranging from 2 to 10
milliseconds. The test was run at a constant pressure of
60 psi, and using heptane as the test fuel. All three
injectors had prediction curves with an r-squared value
of at least 0.9999. The high flow injectors provide ~37%
more fuel flow than the original gasoline injectors do.
The super flow injector supplies ~64% more fuel flow
than the original gas injectors. The graphs obtained
during these tests are shown in Figure 13. Other results
from fuel injector characterization testing show a 2.4%
variance among the fuel injector groups. UTEP has
obtained extra injectors, and with the injector testing
procedure, a fuel injector set with a variation of within
1% will be used in the competition.
ENGINE PERFORMANCE ENHANCEMENTS
The UTEP performance strategy for the 1999 Ethanol
Vehicle Challenge is to maximize engine output at wideopen throttle (WOT), while maintaining economy at
partial throttle operation. In order to accomplish this,
several options are under consideration.
The design of modern combustion engines is a balance
between performance under heavy loads and economy
under normal driving. Larger displacement engines
improve performance under heavy loads, such as hard
acceleration, towing, and travelling up large grades.
However, the efficiency of engines decreases at partload operation, so light load conditions such as highway
driving become very inefficient. This is a result of sparkignition engines throttling air to adjust engine output,
which sharply reduces volumetric efficiency at partialthrottle operation.
Results of FTP baseline
5
4.5
4
grams/mile
3.5
3
HC
CO
NOX
2.5
2
1.5
1
0.5
0
Bag 1
Bag 2
Bag 3
3-Bag Comp.
Figure 15 – Centrifugal supercharger.
ULEV
Figure 14 – Results of the gasoline FTP baseline.
8
Measured Engine Torque and Power for Gasoline Vs Ethanol
BSFC, A/F Ratio, and Volumetric Efficiency of Gasoline Vs Ethanol
350
0.8
90
300
0.7
80
bsfc
Gasoline EngTrq lb-ft
Gasoline EngPwr Hp
150
Gasoline BSFC lb/hph
Ethanol BSFC lb/hph
Gasoline A/F Ratio
40
0.3
Gasoline VolEff %
30
Ethanol EngTrq lb-ft
100
Ethanol A/F Ratio
0.2
Ethanol VolEff %
Ethanol EngPwr Hp
50
0.1
0
1500
2000
2500
3000
3500
4000
4500
5000
5500
50
0.4
Engine Speed (RPM)
20
10
0
1000
6000
vol. eff., AF
60
0.5
200
1000
70
0.6
250
2000
3000
4000
Engine Speed (RPM)
5000
0
6000
Figure 16 – Torque, power, and efficiencies before performance enhancements.
fuel will be added to the intake air, which will eliminate
the lean condition.
The current UTEP strategy uses a centrifugal
supercharger, as seen in Figure 15, to provide ondemand performance and a novel air intake system to
improve partial throttle efficiency.
In order to
accomplish the goal of higher performance on-demand,
while retaining partial-throttle economy, the supercharger is set up to only come on-line at wide open
throttle. Therefore, partial throttle economy is not
penalized for higher performance, but the extra
performance is available when needed.
The team has also installed an air intake system, which
shields the intake air filter from high temperatures found
inside the engine compartment. Engine dynamometer
testing has shown that no performance has been gained
by the addition of the intake system. However, benefits
in the area of fuel consumption will be determined.
DYNAMOMETER TESTS
Current supercharger setup provides an approximate
40% increase in torque output, although we are still
developing our performance strategy.
However,
depending on availability of drivetrain components,
supercharger boost may have to be reduced. Another
possible performance enhancement is the use of a
nitrous oxide injection system. The benefit of the nitrous
oxide system is that it can also be triggered for ondemand operation, and the amount of performance gain
can be carefully set to a desired value by adjusting the
size of the inlet jet.
Shown in the following figures is a comparison of
gasoline versus E85 operation for the GM Gen III
engine. These tests have been performed on a
Superflow 901 water brake engine dynamometer located
within the EAFRL.
Figure 16 shows the results of the E85 conversion
before
any
on-demand
engine
performance
enhancements had been installed. These graphs were
taken from steady state performance mapping with the
engine dynamometer. The E85 conversion provides
slightly higher values of torque and power. This can be
attributed to the higher octane rating of E85 as
compared to unleaded gasoline [6], as well as to a
charge cooling effect of E85. Since E85 has a larger
enthalpy of vaporization when compared to gasoline, a
theoretical performance gain of approximately 4% has
been shown by others [11]. In addition, the higher
octane rating of E85 may provide less timing retard,
which is controlled by the knock sensor. Therefore, as
a result of these properties of E85, a performance gain
of over 4% should be seen for a conversion to E85 [11].
Based on the results of UTEP’s dynamometer testing, a
gain in torque and power of approximately 4.7% has
been realized.
The on-demand performance with the supercharger is
regulated with an electromagnetic clutch system
triggered by a throttle position sensor. A bypass valve
will be installed in order to switch between normally
aspirated intake and forced induction intake. At WOT,
the clutch will engage while almost simultaneously
closing the bypass valve, shifting the intake system into
the forced induction mode. The bypass valve will also
serve a second function as a bleeder valve in the case of
excess pressure.
When the throttle is at WOT, the ECM switches fuel
control to open-loop mode. Therefore, if dynamometer
results dictate, an in-line fuel pump will be added to
boost fuel system pressure when the supercharger is
engaged. With the boost in fuel system pressure, more
9
G a s o lin e V s E t h a n o l E x h a u s t T e m p e r a t u r e F o r C y lin d e r N o . 8
1 6 0 0
G a s o lin e E x h 8
E -8 5 E x h 8
Temperature (F)
1 4 0 0
1 2 0 0
1 0 0 0
8 0 0
6 0 0
4 0 0
2 0 0
55
00
52
50
50
00
47
50
45
00
42
50
40
00
37
50
35
00
32
50
30
00
27
50
25
00
22
50
20
00
17
50
15
00
0
E n g in e S p e e d ( R P M )
Figure 17 – Exhaust temperature comparison for cylinder 8.
and 0.32 jet size on the E85 engine. The smaller 0.22
jet provides a gain of 30 lb-ft of torque (10% gain) and
20 horsepower (8% gain) from the “stock” E85 system.
By placing the larger 0.32 jet size on the system, a gain
of about 105 lb-ft of torque (36% gain) and 75
horsepower (30% gain) have been achieved as
compared to the baseline E85 engine.
However,
depending of the availability of drivetrain components,
the amount of performance gain will have to be limited.
As can be seen in the efficiencies graph of Figure 16,
the air fuel ratio of E85 is lower than the air fuel ratio of
gasoline, as expected. As a result, volumetric efficiency
is decreased due to the increased fuel mass in the
intake air fuel mixture. Since approximately 40% more
fuel is being injected in the E85 engine, coupled with a
4.7% gain in power output, the brake specific fuel
consumption (bsfc) of the E85 engine is approximately
33% higher than the bsfc for gasoline. One interesting
note on the volumetric efficiency curve is the peak at
1500 rpm. These data points have been shown to be
repeatable, which suggests that 1500 rpm matches a
natural frequency in the intake system.
Based on these and other dynamometer results, further
optimization of performance, emissions, and cold start
performance will be taking place prior to the competition.
Complete testing will be performed on all added
components in order to show the benefits of the UTEP
team strategy.
Figure 17 shows the exhaust gas temperature for
ethanol and gasoline. These data have been taken
without
the
addition
of
engine
performance
enhancements, or the air injection system in the
exhaust. This graph suggests that the E85 system is
running lean at higher engine speeds. From readings of
the GM Tech II ECM monitor, it was found that the
injector pulsewidth at high rpms is approximately 25 ms.
It was calculated that near 5000 rpm, the fuel injectors
are always open. Therefore, higher-flow injectors are
necessary to gain further performance and emissions
benefits. At low engine speeds, the graph shows the
cylinders operating at a rich condition, which is ideal
since the ECM is operating in open loop mode.
CONCLUSIONS
As stated in the 1999 Ethanol Vehicle Challenge
Competition Rules and Regulations [1] the EVC is
intended to advance the development of optimized,
dedicated, E85-powered vehicles, specifically in terms of
vehicle performance, emissions control, fuel economy,
and cold starting. In addition, the Challenge is intended
to collect data to define the state of E85 vehicle
technology, and to provide student engineers with a
valuable hands-on learning experience in a real-life
interdisciplinary engineering project. UTEP is proud of
the student effort for this year’s competition and the
team hopes that the UTEP entry exceeds the
expectations of the organizers.
To show the effectiveness of the on-demand
performance enhancement strategy, Figure 18 plots the
results of the addition of a nitrous oxide injection system
to the gasoline and E85 engine. These tests are
acceleration tests performed with the engine
dynamometer in order to simulate actual loading
conditions. With a nitrous oxide injection system, inlet
jets can be modified to provide a desired value of torque
gain. The graphs in Figure 18 show the results of a 0.22
A team of fifteen UTEP students converted the 1999
Chevrolet Silverado with a 5.3L V8 engine to dedicated
E85. The UTEP design strategy combines simplicity and
sound engineering practices with the effective use of
experimentation for design validation. The dedicated
E85 vehicle has superior emissions, cold starting
10
Engine Torque Performance for Gasoline, Gasoline with NOS (0.22 Jet
size), Ethanol, and Ethanol with NOS (0.22 and 0.32 Jet Sizes)
Engine Power Performance for Gasoline, Gasoline with NOS (0.22 Jet
size), Ethanol, and Ethanol with NOS (0.22 and 0.32 Jet Sizes)
350
450
400
300
350
250
300
200
250
Gasoline Acc EngPwr Hp
Gasoline Acc EngTrq lb-ft
200
Gasoline Acc W/0.22 NOS EngPwr Hp
Gasoline Acc W/0.22 NOS EngTrq lb-ft
150
Ethanol Acc EngPwr Hp
100
Ethanol Acc EngTrq lb-ft
100
Ethanol Acc W/0.22 NOS EngPwr Hp
Ethanol Acc W/0.22 NOS EngTrq lb-ft
50
0
1500
150
50
Ethanol Acc W/0.32 NOS EngTrq lb-ft
2000
2500
3000
3500
4000
4500
5000
Ethanol Acc W/0.32 NOS EngPwr Hp
0
1500
5500
Engine Speed (RPM)
2500
3500
4500
Engine Speed (RPM)
5500
Figure 18 – Engine performance enhancement results, NOS system.
the intake manifold. Baseline and modified performance
measurements have been made using an engine
dynamometer, and results indicate as much as a 50%
increase in torque for the existing system.
The
performance tests are continuing and the actual
performance increase at the time of the competition
depends on the final strategy, which undoubtedly
depends on identifying drivetrain components with
required power ratings.
characteristics, and performance when compared to the
original gasoline vehicle.
All fuel system components not E85 compatible have
been replaced or modified. Ethanol-specific light-off and
main catalysts are utilized for emissions reductions, and
an experimentally optimized air injection system rapidly
heats the catalysts for reduced cold start emissions.
Initial fuel enrichment is utilized for starting, which when
combined with air injection, provides rapid catalyst lightoff.
Certain engine control data within the Engine Control
Module (ECM) have been modified based on
experimentation, although many of the stock gasoline
control strategy has been retained. To account for
differences in fuel characteristics, increased mass flow
rate fuel injectors are used. Individual fuel injectors have
been calibrated using a newly developed fuel injector
testing system, and each injector selected for the
conversion provides fuel flow within a 1% tolerance.
Cold starting characteristics are improved by
incorporating a high energy multiple spark ignition (MSI)
system. Cold start testing has been performed within a
cold start test facility and an automated experimental
procedure using instantaneous in-cylinder pressure has
been developed to determine engine start time. Openloop intake air enrichment and starting fuel pulses have
been optimized for E85. Although industry appears to
be reluctant to MSI systems, the UTEP research on E85
supports the findings of others concerning gasoline; that
is, MSI systems successfully extend the lean
flammability limit [2].
The MSI system performs
exceptionally well for E85 and as a result, provides a
low-cost and reliable technique for cold starting.
The complete UTEP Challenge experience includes a
substantial sponsorship effort, a student developed web
page, and an attractive, functional, and consumer
acceptable Chevrolet Silverado pickup. The UTEP
vehicle provides an excellent demonstration of the
benefits derived from an E85 system. Although the
system could be further optimized for dedicated E85, the
system demonstrates benefits derived from a low-cost
conversion of a gasoline vehicle to a dedicated E85
vehicle.
There have been no internal engine modifications to
maintain fuel flexibility.
However, an on-demand
strategy utilizing a centrifugal supercharger at high load
provides increased performance.
The on-demand
strategy restricts the performance enhancements to
operate only at wide open throttle (WOT), thus allowing
emissions and fuel consumption to be optimized at part
load operation and utilizing the higher octane rating of
E85 at high load. A novel intake system that utilizes
ambient air over all driving conditions except WOT has
been designed. At WOT, compressed air is diverted to
ACKNOWLEDGMENTS
The UTEP EVC team would like to thank the numerous
individuals and corporations whose support made the
vehicle conversion possible. First, we would like to
thank the sponsors who provided financial contributions
to the UTEP team. The Official 1999 UTEP EVC Donors
11
REFERENCES
include Autotronic Controls Corporation (Platinum),
Delphi Automotive Systems (Platinum), Yazaki
Corporation (Gold), Emerson Electric (Bronze) and
Phelps Dodge (Bronze). Our official donor levels are
Platinum ($5000 or more), Gold ($3000-$4999), Silver
($2000-$2999), and Bronze ($1000-$1999). The UTEP
team is especially grateful for these significant financial
contributions.
1.
“1999 Ethanol Vehicle Challenge Competition Rules and
Regulations,” Argonne National Laboratory, Center for
Transportation Research, Argonne, IL 60439, April 1999.
2. Bae. C-S., Lee. J-S., Ha, "High-Frequency Ignition
Characteristics in a 4-Valve SI Engine with Tumble-Swirl
Flows," SAE Paper 981433, 1998
3. Crane, M.E., Thring, Podnar, et al. “Reduced Cold-Start
Emissions Using Rapid Exhaust Port Oxidation (REPO) in
a Spark-Ignition Engine,” SAE Paper 970264, Society of
Automotive Engineers, 1997.
4. Dodge, L.G., Shouse, Grogan, et.al, “Development of an
Ethanol-Fueled Ultra-Low Emissions Vehicle,” SAE Paper
981358, 1998 SAE Spring Fuels and Lubricants
Conference, Dearborn, MI, 1998.
5. Matthews, R.D., Internal Combustion Engines and
Automotive Engineering, draft copy of textbook to be
published by Harper-Collins, 1997.
6. Maxwell T.T., and J.C. Jones, Alternative FuelsEmissions, Economics, and Performance, Society of
Automotive Engineers, Warrendale, Pennsylvania, 1995.
7. “NOS Technical Bulletin TB 104,” Nitrous Oxide Systems,
Cypress, CA 90630, 1999.
8. Shayler P.J., Isaacs, Ma, “SI Engine Cold Start Behaviour
and Fuel Calibration,” ImechE Paper C382/009, 1989.
9. “1999 Ethanol Vehicle Challenge Calibration Guide,”
Revision A, General Motors Corporation, January 1999.
10. Acedo, E., Acosta, Holloway, et. al., “Development of the
UTEP E85-Fueled Vehicle,” SAE publication SP-1453,
1998 Ethanol Vehicle Challenge, Society of Automotive
Engineers, 1998.
11. Lutz, B., Reinhart, Ku, et. al., “Conversion of a 1997
Malibu to Dedicated E85 with Emphasis on Cold Start and
Cold Driveablity,” SAE publication SP-1453, 1998 Ethanol
Vehicle Challenge, Society of Automotive Engineers,
1998.
In addition to financial support, UTEP has received
numerous hardware donations as well as technical
support. Our work with MSD (Autotronic Controls
Corporation) and specifically, Mr. Herbert Boerjes in
developing the ignition system has been a very
educational and rewarding experience.
Southwest
Research Institute (SwRI) performed several FTP tests
and provided much technical information. Individuals at
SwRI deserving special recognition include Mr. Patrick
Merritt and Mr. Lee Dodge. Allied Signal Environmental
Catalysts (a division of Delphi) provided the ethanol
specific exhaust catalysts.
Freeway Body Shop
provided the facilities and much support for the UTEP
paint job.
4 Wheel Center of El Paso provided
numerous vehicle accessories. Nitrous Oxide Systems
provided a NOs system and Vortech Superchargers
provided a supercharger for UTEP’s on-demand
performance enhancement strategy.
Additional
companies that provided hardware, technical expertise,
and financial support include: Delphi, Rods and Wheels,
Southwest Chrome.
There are also several individuals and organizations
within UTEP that deserve special recognition. Dr. Lionel
Craver, Mechanical and Industrial Engineering (M&IE)
Department Chair, supports the educational benefits of
the competition, and has provided space, M&IE support,
and a positive voice with the upper administration for this
year’s entry. Several students involved in the project
received financial support from different sources within
UTEP, including the M&IE Department and the College
of Engineering.
UTEP’s Model Institutions for
Excellence Program helped support travel expenses.
The following UTEP employees deserve special
recognition for their countless hours of dedication to the
EVC Team: Mr. Rodolfo Aguilar, Mr. Hans Boenisch, Mr.
Carlos Herrera, Ms. Carmen Mejia, Ms. Monica Mendez,
and Ms. Gwen Pratt.
Finally, the team would like to thank the primary
competition sponsors: the U.S. Department of Energy,
General Motors Corporation, and Natural Resources
Canada for this year’s incredible competition.
In
addition, individuals at Argonne National Laboratory and
in particular, Ms. Cindy McFadden administered the
competition and worked extremely hard to ensure its
success. Her efforts and those of everyone involved in
the organization of the competition are gratefully
acknowledged. All the support for this project has been
appreciated.
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