Vehicular Fuel Consumption
Simulation and Measurement
Dr. Horizon GITANO-BRIGGS
University Science Malaysia
1
Challenges of Field FC and Emissions
Individual Vehicle Variation
Environmental Factors (Temp, Rain…)
Driver Factors (Aggressive, slow)
Load Factors (Hills, passengers)
Traffic Factors (Jammed, or free flowing)
Variation from vehicle to vehicle (identical units)
Tuning, Wear, part-to-part variation
Model to Model variation
Geographic Location Variation
Hills, Loads, Traffic, …
Page 2 of 32
Vehicle FC Modeling
Speed-Load model is useful and fairly accurate –but• No acceleration load prediction
(can be included, but based on what acceleration?)
• No Hill prediction
(again can be included, but what is the topology?)
• Gearing can be included, but depends on shift speeds
– Shift speeds vary by ~2x depending on driver aggression
(3000rpm up shift mellow, 6000 racing)
Vehicle tuning: still need some engine data
Page 3 of 32
Vehicle Power Modeling
S m a ll M o to rc yc le P o w e r/S p e e d C a lc u la to r
600
g m /k W h
Fuel D ens
720
g m /l
35
1
29
k m /h
deg
N
Speed
H ill
F c lim b
Pow er
E s t. F C
9 .7 2
803
482
M ile a g e
52
m /s
W
g m /h r
k m /l
R o llin g R e s is ta n c e
W e ig h t
110
kg
R id e r
C rr
60
0 .0 1 8
kg
C o e fic ie n t
F o rc e
3 0 .0 2
N
7000
6000
M ile a g e
(a s s u m in g g e a rin g g ive s V m a x a t P m a x )
5000
4000
3000
k g /m ^3
m²
C o e fic ie n t
N
2 9 5 B a s e lin e
3 0 1 -3 k g
3 7 0 D e c c rr
O n ly
O n ly
3 2 1 0 .4 A re a
O n ly
0
0 .0
0
0
3 2 1 C d .2 8
3 5 4 3 0 b s fc
O n ly
O n ly
1
2
3 .6
7 .2
30
62
1
4
3
4
1 0 .8
1 4 .4
97
136
13
29
1 8 .0
2 1 .6
2 5 .2
2 8 .8
3 2 .4
7306 .0
3 9 .6
181
234
295
367
451
80 548 90
660
442 BSFC +C R R
5 2 5 P lu s Are a a n d C d
2000
8 8 3 R a d ic le
1 0 2 0 T o ta lly O p t
1000
Ae ro d yn a m ic D ra g
D e n s ity
1 .1 8
A re a
0 .6
Cd
0 .7
Fd
2 3 .4 2
C hange
V e h ic le T o p s p e e d m a c h e s M a x P o w e r
P o w e r D e m a n d (W )
BSFC
0
0
10
20
30
M o d e le d P o w e r D e m a n d
Speed
Speed
Pow er
m /s
kph
W
5
6
7
8
9
40
50
60
10
S p e e d (k p h )
11
0 .6
2 .8
F it
54
91
139
203
282
3 7190 0
494
Vehicle Models can be good predictors of power.
They are less accurate at fuel consumption prediction.
Page 4 of 32
Individual vehicle FC Variation
Vehicle Load con not directly predict FC
Relies on knowledge of engine operating point and efficiency
• Efficiency varies widely based on individual vehicles
operation point (speed vs. torque) even at same power
Page 5 of 32
Effect of Rider Stance, Load, Tire Pressure
Individual vehicle Power and FC
20% ↑ FC
2 x ↑ Power
Page 13 of 29
FC Review
Power = Torque x Speed
FC = Power x BSFC
(Break Specific Fuel Consumption, gm/kWh)
Car on highway: 15Nm, 6000 rpm, BSFC = 600 gm/kWh
P = 15 x 6000 x 2π / 60 = 9.4kW
FC = 600 * 9.4 = 5640 gm/hour
FC = 5640gm / 720gm/liter = 7.8 liters/hour
100km/h => 7.8l/100km
=> 13km/liter
Page 7 of 32
Engine BSFC (gm/kWh)
Maximum Torque Curve (WOT)
Engine Torque
270
290
280
300
350
400
800
Engine Speed
Page 8 of 32
Constant Power Curves
8 kW
Engine Torque
Power:
1 2 3 4 6
Engine Speed
Page 9 of 32
Various Gear Ratios
Engine Torque
For same power BSFC varies from 290 to 350 (ie. 20%)
4th
290
3rd
300
350
2nd
Engine Speed
Page 10 of 32
Engine Technology
Not all technologies will have similar patterns of FC or
emissions (ie. it is hard to generalize FC/Emissions results)
Different technologies give different variations of FC
•Carbureted 2T loses ~35% of fuel unburned typically
•At idle it may be >70% due to miss-firing
•Direct Fuel Injection can run exceptionally lean ay idle - Stratified
Gasoline vs. LPG leakage
•LPG: Based on 1 study ~60% of tanks/systems had significant leaks
•Gasoline systems will have fewer leaks as more noticeable, but suffer
from more “pilferage”
Page 11 of 32
Idle Combustion Pressure Comparison
Pressur e (100kPa)
)
30
Carbureted: fires 1 out of 4 cycles
25
20
3 x misfires
3 x misfires
15
10
5
0
0
0 .1
0 .2
0 .3
0 .4
0 .5
T im e ( s )
Late combustion
Pressure (100 kPa)
30
Direct Fuel Injection: More consistent
25
20
15
10
5
0
0
0.1
0.2
0.3
0.4
0.5
Time (s)
Page 12 of 32
Fleet Vehicle FC Variation
Variation: Gearing, Tire Size, Replacement Parts, Wear
•Vehicle tuning varies (7% are grossly mistuned)
•Driver behavior variation: 2x variation in acceleration
One study found FC ok in city but bad in rural because
gearing was the same, and engines were revving too high
for rural highway speeds
Re-geared for highway speeds and FC greatly improved
•Probably require>30 vehicle samples for any reasonable
estimates
Page 13 of 32
Dyno vs Road Testing
Obvious environmental factors: Temp, rain, road surface
•2ndary: Engine temps
•Even with careful control may still have ~10% variation
(road – dyno)
•While dyno tests may not give exactly the same FC
numbers as road tests, they are pretty good at vehicle to
vehicle comparisons
Strive to get a dyno test to match the road FC, but don’t
stress! The vehicle to vehicle comparison should still be
valid unless the dyno test is totally inappropriate!
Page 14 of 32
Dynamometry Measurements: good for comparisons
Fuel economy of 4-stroke and 2-stoke
motorcycles
Vehicle fuel economy as function of
motorcycle age
Page 24 of 29
Dynamometry Measurements: good for comparisons
Fuel economy versus engine size
Fuel economy by manufacturer
Page 25 of 29
Dynamometry Studies
part throttle resulting in
high pumping losses
extra work done to overcome
the larger aerodynamic drag
Optimum
speed for
best FE
Some studies are much easier to do on a dynamometer
Page 15 of 29
Dynamometry Studies
10
7000
Power (at Dyno)
9
6000
8
Torque (Nm)
Torque
6
4000
5
3000
4
3
2
1
0
4000
Optimum
speed for
Red lines - Carbureted
Blue Lines - EFI
best FE
Both give same power and torque WOT
5000
6000
7000
Power (W)
5000
7
2000
1000
8000
9000
0
10000
Engine Speed (rpm)
Technology comparison: Carb vs EFI
Page 15 of 29
ECER40
V eloc ity(km/h)
Drive Cycle Comparison
60.0
40.0
20.0
0.0
0
50
100
150
200
Time(s )
M’sian
Urban Cycle
M’sians accelerate more aggressively, faster and spend less
time stopped
Page 19 of 32
Drive Cycle Analysis: Malaysia
• 600 motorcycle survey
• Average mileage 5500km/year
Similar speeds and
accelerations
Page 20 of 32
FUEL CONSUMPTION COMPARISON: Chassis Dyno vs. On-Road
Drive cycle
Distance
(m)
Time
Fuel
(s)
Consumed (g)
Chassis Dyno
Mileage (km/L)
On-road
Mileage
(km/L)
Suburban
4643
442
73.9
45.2
50.8
Highway
25260
1589
451.4
40.3
43.6
Difference (%)
11
8
The vehicle was transient dyno tested on a representative drive cycle, and
compared with on the road fuel consumption for that mode of driving.
Typically there is a 10% difference between the 2 methods.
Page 21 of 29
Fuel Consumption and Emissions Factors
Typical “balanced” drive cycle => 42.8 km/l
Annual mileage ~ 5,500km/year
 128.5 l/vehicle per year
 5,000,000 bbl/year total fuel consumption by motorcycles
in Malaysia
Typical emissions (New carbureted small 4T motorcycles):
gm/km
kg/vehicle/year
kTons/year (Msia)
CO: 7.0
38
308
HC: 0.7
3.8
31
NOx: 0.15
0.83
6.6
CO2: 50
275
2200
Page 22 of 32
Effect of Technologies: Carb vs EFI
Even if the test pattern doesn’t match the road cycle
exactly, the differences between various technologies
should be obvious:
Emissions (gm/km) on the ECE-R40 Test:
Carbureted
EFI
CO:
7.0
1.1
HC:
0.7
0.24
NOx:
0.15
0.08
CO2:
50
55
Page 23 of 32
Field FC Measurements
Individual tank fill-ups variation is large (>10%)
•Probably requires ~10 tank fills (Empty to Full 10x)
•Data taking sometimes questionable (does the recorder
care about data quality?)
Running with a calibrated fuel bottle will give accurate
results for a given drive. This is SOP for Shell Eco
Marathon and similar “eco races”.
Page 24 of 32
Field Vehicle Measurements
GPS is ok for speed, but it may overestimates speed when
slow (dither)
•Wheel sped pick better: gives good V and A and distance
•No hill, no load info
Simple, inexpensive data loggers can track a vehicles
movement for months with high resolution.
Page 25 of 32
Data Collection: Wheel Speed pickup
Target
Sensor
Inductive sensor reads signal
from 2 targets on rear wheel,
180 degrees apart
Data from the speed pickup is
stored in the portable data
logger at 10Hz and later
downloaded into the computer.
• RPM vs Time
Page 26 of 32
Motorcycle Roll Down Test: GPS vs Wheel Speed
Aerodynamic
resistance
dominates
Notice Model and Wheel Data
overlay (good agreement)
Rolling resistance
dominates
Page 9 of 29
Instrumentation: Advanced Concepts
Torque sprocket: Measures both speed and torque at wheel
• Includes hill and load effects (but not engine efficiency)
• Torque Spkt + engine speed (from generator signal) can be
decent predictor of engine operating condition (speed
torque) and thus FC
Outer section is separate from
inner section. Torque
compresses springs, allowing
outer section to rotate with
respect to inner section. Features
on both sections are detected by
speed pickup.
Page 28 of 32
Instrumentation: Advanced Concepts
Torque sprocket: Speed, Torque, and Acceleration (from V)
30
s p e e d (k m /h )
25
20
15
10
5
0
0
5
10
15
20
25
30
35
40
45
tim e (s )
200
180
160
T o rq u e ( N m )
140
120
100
80
60
40
20
0
0
5
10
15
20
25
30
35
40
45
t im e ( s )
Page 29 of 32
Instrumentation: Advanced Concepts
In fuel injected vehicles the ECU “knows” how much fuel is
being injected. OBD 2 (On Board Diagnostics) Vehicles can
have FC read directly from the ECU
On non-OBD EFI systems Injection Duration can
easily be measured and combined with injector
calibration to get a good FC number
Carbureted vehicles can be instrumented with EFI sensors:
•Measure engine speed and throttle position
•Can back-calculate FC accurately if you have “mapped”
the engine
Page 30 of 32
Instrumentation: Advanced Concepts
In EFI systems the injector does not open or close instantly.
The injector calibration curve will give the fuel delivered based on an
injection duration (signal) including both of these effects.
Injector Signal
Delivered Fuel
Flow Rate
Injector Signal Duration
Page 31 of 32
Instrumentation: Advanced Concepts
2-T LPG EFI used for fuel tracking in bi-fuel motorcycle.
In gasoline mode (carbureted) can record info for gasoline
FC via separate calculation
Page 32 of 32
Implications for CDMs
Vehicle Measurement are crucial:
Wheel speed pickup V and A, and distance are reliable
Measuring Torque and speed we can estimate FC well
Engine Measurement are getting better:
TPS + Engine Speed, and Temp
With a “calibrated” vehicle we can accurately get the FC
Higher Resolution data, but on a limited number of vehicles?
Road “gas bottle” test still most reliable:
Still will have some variation so need several runs.
~30 vehicles to get a good idea of the FC for a given senario.
Page 33 of 32
Conclusions
We can (and should) use standard tests to compare the
emissions/FC benefits of various technologies
These tests should be as close to the real operating conditions as
possible although standard (ie. dyno) tests may not correlate perfectly
with field tests
Field tests are a good idea (for final confirmation) but must
be well controlled:
–Fuel metering should be very carefully controlled
–Environmental conditions, loads, speeds, … should all be controlled
In-Stitu Instrumentation for monitoring actual usage is
probably the best way to go in the long run. This may
require further development of instrumentation.
Page 34 of 32
Thank You
Contacting Us
For more information please contact us via:
University Science Malaysia
HorizonUSM@yahoo.com
Focus Applied Technologies
Lot 1174 Jalan Hutan Lipur
Kpg. Sg. Buaya
Nibong Tebal 14300
Penang, Malaysia
+ (6016) 484-6524 (Voice)
+(604) 594-1025 (Fax)
Horizon@FocusAppliedTechnologies.com
www.FocusAppliedTechnologies.com
36
Motorcycle Power Demand
Coefficient
of drag, Cd
• frontal area
• vehicle mass
Coefficient of
rolling
resistance,
Crr
• rider and payload mass
• tire pressure
Page 4 of 29
Parameters Affecting Fuel Consumption
Factors
Effects
Motorcycle
Condition
Driving pattern
Road
Condition
Environmental
Condition
Vehicle’s
Emission
Fuel
Consumption
Operational
Cost
Page 2 of 29
Motorcycle Driving Patterns Comparison
Malaysia
• Aggressive acceleration/breaking
• Predominantly as commuters also
as delivery and even in
construction
• Very different “rules” from cars
• Lots of Motorcycle-only
infrastructure
West (US, Europe)
• More steady cruising with mild
accelerations
• Mainly for leisure and occasionally
for commuting
• Follow same rules as cars
Page 39 of 32
Gear Ratio Effect: +/- 50% effect on FC
Typical Seasoned Motorcycle
Page 14 of 29