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Vehicular Fuel Consumption Simulation and Measurement

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

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

Speed-Load model is useful and fairly accurate –but-
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
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
Power Required for constant cruising , @60km/h best 1.7kW Worst 3.4kW Avg 2 x ↑ Power Page 13 of 29 6

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

Maximum Torque Curve (WOT)
Engine BSFC (gm/kWh) Maximum Torque Curve (WOT) 270 280 290 Engine Torque 300 350 400 800 Engine Speed Page 8 of 32

Constant Power Curves Power: 1 2 3 4 6 8 kW Engine Torque Engine Speed
Page 9 of 32

For same power BSFC varies from 290 to 350 (ie. 20%)
Various Gear Ratios For same power BSFC varies from 290 to 350 (ie. 20%) 290 4th Engine Torque 300 3rd 350 2nd Engine Speed Page 10 of 32

Different technologies give different variations of FC
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
Carbureted: fires 1 out of 4 cycles 3 x misfires 3 x misfires Late combustion Direct Fuel Injection: More consistent 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

Obvious environmental factors: Temp, rain, road surface
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 45km/L, 35km/L 2-stroke engines suffer fuel short circuiting during the scavenging process resulting in lower fuel mileage and higher exhaust emissions low price and relatively high performance the increasing size of engines over the years, cc => cc Page 24 of 29 15

Dynamometry Measurements: good for comparisons
Fuel economy versus engine size Fuel economy by manufacturer small displacement and low power, such as the Honda C70, which run very efficiently as they operate at larger throttle settings and nearer to their best BSFC Larger cc at lower throttle with more pumping losses resulting to a less efficient motorcycle 45km/L Avg 55km/L Honda Page 25 of 29 16

Some studies are much easier to do on a dynamometer
Dynamometry Studies part throttle resulting in high pumping losses extra work done to overcome the larger aerodynamic drag Optimum speed for best FE From Optimum Gearing Best Some studies are much easier to do on a dynamometer Page 15 of 29 17

Technology comparison: Carb vs EFI
Dynamometry Studies Optimum speed for best FE From Optimum Gearing Best Technology comparison: Carb vs EFI Page 15 of 29 18

Drive Cycle Comparison
ECER40 M’sian Urban Cycle M’sians accelerate more aggressively, faster and spend less time stopped 2 types Synthesized vs actual 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 (s) Fuel Consumed (g) Chassis Dyno Mileage (km/L) On-road Mileage (km/L) Difference (%) Suburban 4643 442 73.9 45.2 50.8 11 Highway 25260 1589 451.4 40.3 43.6 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: HC: NOx: CO2: 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: HC: NOx: CO2: Page 23 of 32

Individual tank fill-ups variation is large (>10%)
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
Sensor Target Data from the speed pickup is stored in the portable data logger at 10Hz and later downloaded into the computer. RPM vs Time Inductive sensor reads signal from 2 targets on rear wheel, 180 degrees apart Page 26 of 32

Motorcycle Roll Down Test: GPS vs Wheel Speed
Notice Model and Wheel Data overlay (good agreement) Aerodynamic resistance dominates Rolling resistance dominates GPS over estimate, spatial dither codes Page 9 of 29 27

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) 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 Flow Rate Delivered Fuel 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 Focus Applied Technologies Lot 1174 Jalan Hutan Lipur Kpg. Sg. Buaya Nibong Tebal 14300 Penang, Malaysia + (6016) (Voice) +(604) (Fax)

Motorcycle Power Demand
Coefficient of drag, Cd frontal area vehicle mass rider and payload mass tire pressure Coefficient of rolling resistance, Crr Page 4 of 29

Parameters Affecting Fuel Consumption
Factors Effects Motorcycle Condition Vehicle’s Emission Driving pattern Fuel Consumption Road Condition Operational Cost Environmental Condition 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 Steady state cruising load were applied FC measured as function of each Gear. Best Near ~ 600g/kWh Typical best BSFC for engine like this ~300g/kWh ( near intermediate speed ) Page 14 of 29 40

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