1 Vehicular Fuel Consumption Simulation and Measurement Dr. Horizon GITANO-BRIGGS University Science...

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Vehicular Fuel ConsumptionSimulation and Measurement

Dr. Horizon GITANO-BRIGGSUniversity Science Malaysia

http://www.sae.org/

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, …

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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

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Vehicle Power Modeling

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Vehicle Models can be good predictors of power.

They are less accurate at fuel consumption prediction.

Small Motorcycle Power/Speed CalculatorBSFC 600 gm/kWh

Fuel Dens 720 gm/lSpeed 35 km/h Mileage ChangeHill 1 degFclimb 29 N

9.72 m/s 295 Baseline 0.6Power 803 W 301 -3kg Only Speed Speed Power 2.8Est. FC 482 gm/hr 370 Dec crr Only m/s kph W FitMileage 52 km/l 321 0.4 Area Only 0 0.0 0 0Rolling Resistance 321 Cd .28 Only 1 3.6 30 1Weight 110 kg 354 30 bsfc Only 2 7.2 62 4Rider 60 kg 442 BSFC+CRR 3 10.8 97 13Crr 0.018 Coeficient 525 Plus Area and Cd 4 14.4 136 29Force 30.02 N 883 Radicle 5 18.0 181 54

1020 Totally Opt 6 21.6 234 91Aerodynamic Drag 7 25.2 295 139Density 1.18 kg/m^3 8 28.8 367 203Area 0.6 m² 9 32.4 451 282Cd 0.7 Coeficient 10 36.0 548 379Fd 23.42 N 11 39.6 660 494

Modeled Power Demand

0

1000

2000

3000

4000

5000

6000

7000

0 10 20 30 40 50 60 70 80 90 100Speed (kph)

Po

wer

De

ma

nd

(W

)

Vehicle Top speed maches Max Power(assuming gearing gives Vmax at Pmax)

Individual vehicle FC Variation

Vehicle Load con not directly predict FCRelies on knowledge of engine operating point and efficiency

• Efficiency varies widely based on individual vehicles operation point (speed vs. torque) even at same power

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Effect of Rider Stance, Load, Tire Pressure Individual vehicle Power and FC

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34.3

41.1 41.8

0

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15

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25

30

35

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45

Worst Average Best

Fu

el E

con

om

y (k

m/L

)

2 x ↑ Power

20% ↑ FC

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

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Engine BSFC (gm/kWh)

Maximum Torque Curve (WOT)

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Eng

ine

Tor

que

Engine Speed

270

280290

300350

400

800

Constant Power Curves

Power:

1 2 3 4 6 8 kW

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Eng

ine

Tor

que

Engine Speed

Various Gear Ratios

For same power BSFC varies from 290 to 350 (ie. 20%)

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Eng

ine

Tor

que

Engine Speed

290

300350

4th

3rd

2nd

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”

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Idle Combustion Pressure Comparison

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0

5

10

15

20

25

30

0 0.1 0.2 0.3 0.4 0.5

Time (s)

Pressu

re (

100kP

a)

)

0

5

10

15

20

25

30

0 0.1 0.2 0.3 0.4 0.5

Time (s)

Pressu

re (

100 k

Pa)

Carbureted: fires 1 out of 4 cycles

Direct Fuel Injection: More consistent

3 x misfires 3 x misfires

Late combustion

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 speedsRe-geared for highway speeds and FC greatly improved

•Probably require>30 vehicle samples for any reasonable estimates

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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!

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Dynamometry Measurements: good for comparisons

0

10

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50

4 S TR OK E 2 S TR OK EE NG INE T YP E

Fu

el E

con

om

y (

KM

/LIT

ER

)

Fuel economy of 4-stroke and 2-stoke motorcycles

Vehicle fuel economy as function of motorcycle age

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Fuel economy versus engine size

0

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HO NDA MO DE NAS S UZ UK I Y AMAHA

MANUF AC TUR E RF

uel E

cono

my

(KM

/LIT

ER

)

Fuel economy by manufacturer

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Dynamometry Measurements: good for comparisons

Dynamometry Studies

010203040506070

0 20 40 60 80

Speed (km/h)

Fu

el E

con

om

y (k

m/L

)

part throttle resulting in high pumping losses

extra work done to overcome the larger aerodynamic drag

Optimum speed for best FE

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Some studies are much easier to do on a dynamometer

Dynamometry Studies

Optimum speed for best FE

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Technology comparison: Carb vs EFI

0

1

2

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7

8

9

10

4000 5000 6000 7000 8000 9000 10000

Engine Speed (rpm)

To

rqu

e (N

m)

0

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3000

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5000

6000

7000

Po

wer

(W

)

Power (at Dyno)

Torque

Red lines - CarburetedBlue Lines - EFIBoth give same power and torque WOT

Drive Cycle Comparison

ECER40

M’sian Urban Cycle

M’sians accelerate more aggressively, faster and spend less time stopped

0.0

20.0

40.0

60.0

0 50 100 150 200

Time(s )Ve

loci

ty(k

m/h

)

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Drive Cycle Analysis: Malaysia

• 600 motorcycle survey• Average mileage 5500km/year

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Urban31%

Suburban41%

Rural17%

Highw ay11%

Similar speeds and accelerations

FUEL CONSUMPTION COMPARISON: Chassis Dyno vs. On-Road

Drive cycleDistance

(m)Time

(s)Fuel

Consumed (g)Chassis Dyno

Mileage (km/L)

On-road Mileage (km/L)

Difference (%)

Suburban 4643 442 73.9 45.2 50.811

Highway 25260 1589 451.4 40.3 43.68

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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.

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

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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

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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”.

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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.

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Data Collection: Wheel Speed pickup

Sensor

Target

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 of 32

Motorcycle Roll Down Test: GPS vs Wheel Speed

Aerodynamic resistancedominates

Rolling resistancedominates

Notice Model and Wheel Data overlay (good agreement)

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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

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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.


Torque sprocket: Speed, Torque, and Acceleration (from V)

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0

5

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0 5 10 15 20 25 30 35 40 45time (s)

sp

ee

d (

km

/h)

0

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60

80

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120

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0 5 10 15 20 25 30 35 40 45

time (s)

To

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m)


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

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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.

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Del

iver

ed F

uel

Injector Signal Duration

Injector Signal

Flow Rate


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

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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.

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Conclusions

We can (and should) use standard tests to compare the emissions/FC benefits of various technologiesThese 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.

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Thank You

36

Contacting Us For more information please contact us via:

University Science [email protected]

Focus Applied TechnologiesLot 1174 Jalan Hutan LipurKpg. Sg. BuayaNibong Tebal 14300Penang, Malaysia

+ (6016) 484-6524 (Voice)+(604) 594-1025 (Fax)

Horizon@FocusAppliedTechnologies.comwww.FocusAppliedTechnologies.com

mailto:[email protected]

http://www.focusappliedtechnologies.com/

Motorcycle Power Demand

• frontal area

• vehicle mass

• rider and payload mass

• tire pressure

Coefficient of rolling

resistance, Crr

Coefficient of drag, Cd

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Parameters Affecting Fuel Consumption

Motorcycle Condition

Driving pattern

Road Condition

Environmental Condition

Fuel Consumption

Vehicle’s Emission

Operational Cost

Factors Effects

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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

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0

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0 10 20 30 40 50 60 70 80Speed (km/h)

BS

CF

(g

/kW

h)

Gear 4

Gear 3

Gear 2

Gear 1

Poly. (MIN BSFC)

Gear 1 Gear 2 Gear 3 Gear 4

FIT

Gear Ratio Effect: +/- 50% effect on FC

Typical Seasoned Motorcycle

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1 Vehicular Fuel Consumption Simulation and Measurement Dr. Horizon GITANO-BRIGGS University Science...

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