Fuel Economy Research Articles

Analysis of the Deviation Factors between the Actual and Test Fuel Economy

The Worldwide harmonized Light duty Test Procedure saw its light first as the United Nations Economic Commission for Europe Global Technical Regulation in 2017. However, it remains unclear how much the deviation is between the actual and test fuel economy. In this study, we analyzed the deviation between the actual and test (JC08 and WLTC) fuel economy and examined how well regional characteristics such as average travel speed and temperature could explain the deviation using 182–1035 drivers and 19–52 car models data in Japan. As a result, (1) more than a 30% discrepancy was observed between the actual and JC08 mode test fuel economy, and the higher the test fuel economy, the larger the deviation; (2) regarding WLTC mode fuel economy, the deviation is 19% and constant regardless of the test fuel economy; (3) average travel speed and temperature can explain approximately 8% of the discrepancy.

The Effects of Ultra-Low Viscosity Engine Oil on Mechanical Efficiency and Fuel Economy

The development of a sustainable powertrain requires improved thermal efficiency. Reducing frictional power losses through the use of ultra-low viscosity oil is one of the most effective and economical ways. To assess the potential for efficiency enhancement in a new generation of future engines using low-viscosity oils, a technical analysis was conducted based on numerical simulation and theoretical analysis. This study proposes a numerical method coupling the whole multi-dynamics model and lubrication model under mixed lubrication regimes. Then, load distribution was calculated numerically and verified experimentally. Finally, this paper compares the bearing load and frictional energy loss of the main bearings when using The Society of Automotive Engineers (SAE) 15W40 and SAE 0W20 oil. The results indicate that the application of ultralow-viscosity lubricant can reduce the hydraulic friction loss up to 24%, but the asperity friction loss would increase due to the reduction in load capacity. As a result, the design of a new generation of high efficiency internal combustion engines requires careful calculation and design to balance the trade-off relations between hydraulic friction and asperity friction.

Lean-Stratified Combustion System with Miller Cycle for Downsized Boosted Application - Part 2

<div class="section abstract"><div class="htmlview paragraph">Automotive manufacturers relentlessly explore engine technology combinations to achieve reduced fuel consumption under continued regulatory, societal and economic pressures. For example, technologies enabling advanced combustion modes, increased expansion to effective compression ratio and reduced parasitics continue to be developed and integrated within conventional and hybrid propulsion strategies across the industry. A high-efficiency gasoline engine capable for use in conventional or hybrid electric vehicle platforms is highly desirable. This paper is the second of two papers describing the multi-cylinder integration of a technology package combining lean-stratified combustion with Miller cycle for downsized boosted applications. The first paper describes the design, analysis and single-cylinder testing conducted to down-select the combustion system deployed to the multi-cylinder engine. This paper defines a light-duty engine package capable of achieving a 35% fuel economy improvement at US Tier 3 emission standards over a naturally aspirated stoichiometric baseline vehicle. A multi-mode combustion system was developed enabling highly efficient lean-stratified operation at light-load and stoichiometric Miller-cycle operation at mid- to high-loads. A central direct-injection four-valve layout was designed with high-tumble ports and a bowl-in-piston capable of stable operation under highly dilute mixtures when properly matched to fuel spray characteristics, injection strategy, and a high-energy ignition system. Boost system layout and base engine architecture were selected to minimize parasitics and maximize aftertreatment effectiveness. A multi-cylinder engine was developed and calibrated over a steady-state map. Results fed vehicle simulations over the EPA city and highway test cycles to predict the fuel economy improvement and tailpipe emissions potential. Fuel economy improvements over the baseline vehicle were projected at 42% and 39% for active-urea and passive-ammonia SCR aftertreatment systems respectively. Controls complexity to achieve regulatory compliance and the cost of the lean aftertreatment system were identified as the primary challenges to commercial viability.</div></div>

Optimal Design of an Adaptive Cruise Control System for Driving Comfort and Fuel Economy


 
 
 Adaptive Cruise Control (ACC) is introduced to allow the subject vehicle to follow a target vehicle at a pre-selected time gap, up to a driver-selected velocity by controlling the engine and/or service brakes as defined in SAE J2399. A typical ACC ensures passenger comfort by minimizing the subject vehicle’s rate of acceleration and deceleration when following a target vehicle. However, if the ACC rate of velocity change is too slow, the subject vehicle might not be able to follow the target vehicle at the set time-gap. On the other hand, if the ACC responds too quickly to the changes in the target vehicle velocity, it might cause passenger discomfort and reduce energy efficiency due to the high rate of acceleration and deceleration. Thus, a research gap in ACC is identified, and this paper seeks to investigate an optimal ACC for driving comfort and fuel economy. This paper models the performance of a passenger vehicle with ACC using feedback control in Matlab Simulink. Three types of ACC control systems are simulated and compared; proportional-integral (PI) control, fuzzy logic control (FLC), and Linear-Quadratic Regulator (LQR). The performance of the control systems is simulated using set test scenarios, and an optimal ACC design is selected based on minimum acceleration, deceleration, and jerk performance, as defined in ISO 15622, following performance and minimum fuel consumption. Results show that the LQR controller has the best performance in meeting the ISO 15622, the lowest target vehicle the following root mean square error (RMSE), and the second-lowest New European Drive Cycle (NEDC) urban cycle fuel consumption.
 
 

Effects of driving conditions on secondary aerosol formation from a GDI vehicle using an oxidation flow reactor

A comprehensive study on the effects of photochemical aging on exhaust emissions from a vehicle equipped with a gasoline direct injection engine when operated over seven different driving cycles was assessed using an oxidation flow reactor. Both primary emissions and secondary aerosol production were measured over the Federal Test Procedure (FTP), LA92, New European Driving Cycle (NEDC), US06, and the Highway Fuel Economy Test (HWFET), as well as over two real-world cycles developed by the California Department of Transportation (Caltrans) mimicking typical highway driving conditions. We showed that the emissions of primary particles were largely depended on cold-start conditions and acceleration events. Secondary organic aerosol (SOA) formation also exhibited strong dependence on the cold-start cycles and correlated well with SOA precursor emissions (i.e., non-methane hydrocarbons, NMHC) during both cold-start and hot-start cycles (correlation coefficients 0.95–0.99), with overall emissions of ∼68–94 mg SOA per g NMHC. SOA formation significantly dropped during the hot-running phases of the cycles, with simultaneous increases in nitrate and ammonium formation as a result of the higher nitrogen oxide (NOx) and ammonia emissions. Our findings suggest that more SOA will be produced during congested, slow speed, and braking events in highways.

Fuel economy, NOx emissions and lean NOx trap efficiency: Lessons from current driving cycles

Transport sector is within a profound changing period, but diesel engines are still called to play a significant role in future supported on their solid share in many regions and superior thermal efficiency compared to spark-ignited engines. This work identifies the parameters that most affect fuel consumption and NOx emissions on a diesel passenger car equipped with a lean NOx trap under different driving cycles and ambient temperatures. High average vehicle velocity was beneficial to reduce the fuel consumed per kilometer. The driving dynamics was of little importance, easily counteracted by a higher thermal efficiency, higher engine temperature (because of a longer trip) or/and an efficient gear shifting strategy. Moreover, at low ambient temperature the latter two factors doubled their weight on fuel economy. Regarding tailpipe NOx, keeping high aftertreatment performance was crucial. For this, low engine-out NOx emissions were four times more important than exhaust temperature or flow rate.

Impact of Active Control Turbocharging on the Fuel Economy and Emissions of a Light-Duty Reactivity Controlled Compression Ignition Engine: A Simulation Study

While forced induction strategies such as turbocharging can increase the power output and extend the load limit of engines operating on low temperature combustion strategies such as reactivity controlled compression ignition, the low exhaust enthalpy prevalent in these strategies requires the use of high backpressures to attain high turbocharger efficiencies, leading to high pumping losses and in turn poor fuel economy. Hence, there is a need to improve the exhaust energy utilization by the turbocharger such that the negative effects of the high backpressure requirements are offset. One turbocharger operating strategy that has the potential to enhance exhaust enthalpy conversion by the turbine is active control turbocharging (ACT), in which the rack position of a variable geometry turbocharger (VGT) is actuated using a continuously varying sinusoidal signal whose frequency is proportional to engine speed. In this study, the impact of ACT on turbocharger performance and fuel economy of a light-duty reactivity controlled compression ignition engine equipped with a VGT is investigated through coupled GT-POWER/KIVA-3V simulations at a medium-load cruise operating condition. A design of experiments study was executed in which the rack position amplitude and phase angle were independently varied, and the turbine efficiency, compressor efficiency, crankshaft torque, and brake specific fuel consumption were tracked for each run. The results show that ACT operation significantly increased the torque output while improving fuel economy over baseline VGT operation, but the range of actuation signal amplitude ratio was limited to 40% of the maximum amplitude possible due to peak cylinder pressure and peak pressure rise rate constraints. It is also shown that the impact of signal phase angle on turbocharger efficiency and overall system performance is not as significant as the amplitude ratio. The best fuel economy improvement over the baseline VGT operation at cruise conditions was observed at 40% amplitude ratio and 0° phase angle, and this value was 2.8%.

Implementation and System-Level Modeling of a Hardware Efficient Cell Balancing Circuit for Electric Vehicle Range Extension

This article presents a novel hardware-efficient battery balancing circuit for electric vehicle batteries that uses the low-voltage battery as a convenient source and sink for balancing. Compared to existing techniques, the proposed topology strikes a balance between the current industry standard of passive balancing and high component-count, high-cost solutions. For a battery pack consisting of n cells in series within m modules, the proposed design uses (n +1) bilateral switches for cell selection, and m low-voltage isolated dc/dc converters for cell balancing. Balancing can occur quickly during driving as the circuit can transfer energy between nonadjacent cells concurrently throughout the pack. This article presents the design, control, simulation results, and experimental results of the proposed architecture. Furthermore, system-level vehicle modeling shows an increase in driving range of 1.8%-20.1% for different balancing parameters on repeated Urban Dynamometer Driving Schedule and Highway Fuel Economy Driving Schedule cycles for an end-of-life pack, compared to passive balancing, which does not charge cells while driving.

A Simple and Safe Strategy for Improving the Fuel Economy of a Fuel Cell Vehicle

A new real-time strategy is proposed in this article to optimize the hydrogen utilization of a fuel cell vehicle, by switching the control references of fueling regulators, based on load-following. The advantages of this strategy are discussed and compared, with advanced strategies that also use the aforementioned load-following mode regulator of fueling controllers, but in the entire loading range, respectively, with a benchmark strategy utilizing the static feed-forward control of fueling controllers. Additionally, the advantages of energy-storage function in a charge-sustained mode, such as a longer service life and reduced size due to the implementation of the proposed switching strategy, are presented for the dynamic profiles across the entire load range. The optimization function was designed to improve the fuel economy by adding to the total power of the fuel utilization efficiency (in a weighted way). The proposed optimization loop will seek the reference value to control the fueling regulator in real-time, which is not regulated by a load-following approach. The best switching threshold between the high and low loading scales were obtained using a sensitivity analysis carried out for both fixed and dynamic loads. The results obtained were promising—(1) the fuel economy was two-times higher than the advanced strategies mentioned above; and (2) the total fuel consumption was 13% lower than the static feed-forward strategy. This study opens new research directions for fuel cell vehicles, such as for obtaining the best fuel economy or estimating fuel consumption up to the first refueling station on the planned road.

Fuel Economy and Emissions of E85 in Passenger Cars - A Move towards Flex Fuel Vehicle

<div class="section abstract"><div class="htmlview paragraph">Many countries are developing strategies to curb the consumption of fossil fuels, and to increase the share of alternative fuels such as alcohols, natural gas, fuel cell and electricity in the energy pool in order to improve energy security and reduce atmospheric pollution. Alcohol fuels are promising one and it has been widely used in many countries as blending component for gasoline. Ethanol has a high-octane number but it has a lower calorific value than gasoline. The performance of engine may be affected with higher percentage of ethanol in gasoline due to demand for larger quantity of fuel that could not be supplied by vehicles which are tuned to run on gasoline only. In this study, a second electronic control unit (ECU) was installed in series with the existing commercial or primary ECU and an ethanol sensor was installed in the fuel line. This secondary ECU modulates the fuel injection pulse width of the primary ECU depending on ethanol concentration in the fuel. The vehicle studies were carried out using Indian automotive gasoline meeting IS:2796 specification and 85% ethanol blended gasoline (E85) in a climatically controlled chassis dynamometer lab in which test cell temperature maintained at 25±1 °C throughout the test. Modified Indian Driving Cycle tests (MIDC) and constant speed tests were carried out using E85 and commercial gasoline to investigate the fuel economy, gaseous mass emissions, particulate emission in terms number and size characteristics. Gaseous emission was reduced up to 30% with the penalty of reduction in fuel economy by approximately 30% over the MIDC. The vehicle power was maintained while using both fuels at respective constant speeds during the road load simulation cycles however an increase in fuel consumption was observed with E85. The tailpipe exhaust particle emission measurement had shown up to 50% reduction in exhaust particulate emissions with E85. This study demonstrates the potential of using higher blends of ethanol up to E85 and meeting power or speed demand at constant speeds and driving cycle tests.</div></div>

Improving Ride Comfort and Fuel Economy of Connected Hybrid Electric Vehicles Based on Traffic Signals and Real Road Information

Wireless communication technology has promoted the development of connected hybrid electric vehicles (CHEVs). With traffic signal information, the fuel economy of CHEVs can be improved via optimal speed planning. However, the road environment in most existing studies is unreal and riding comfort is ignored. Therefore, this paper uses the real phase and position information of traffic lights to establish a road model and proposes a multi-objective hierarchical optimal (MOHO) strategy. First, a speed planning module is developed as the upper layer. By integrating speed constraints, slope, and traffic light information, a model predictive control (MPC)-based speed planning strategy (SPS) is developed, which improves riding comfort. Second, an energy management module is developed as the lower layer. An adaptive equivalent consumption minimization strategy (A-ECMS)-based energy management strategy (EMS) is proposed, which achieves the optimal power distribution. The results show that the proposed MOHO strategy can improve riding comfort and fuel economy while avoiding vehicle stopping at the signalized intersection under two different road conditions.

Muddy foil: a history of extraction and resistance in the lower Mississippi River Delta

ABSTRACT This article considers Mississippi River Mud as an analytic for unruly ontologies and fugitive spaces. Historic discourses around mud—and by extension, muddy spaces—were mapped onto lawless, not-fully-humans who occupied them. They reflected efforts to impose rational order and naturalize a political economy of monoculture, river shipping, and fossil fuels. This episteme, which reduces complex ecologies to agents of capital extraction, has transformed the once alluvial forests and marshlands of south Louisiana into subsiding oil and gas fields, abandoned wells, and eroding canals. An explication of mud by communication scholars ruptures this discourse in imagining alternative ways of living.

Evaluation on the Fuel Economy of Automated Vehicles with Data-Driven Simulation Method

With more commercialized automated vehicles (AVs) shortly entering the market, evaluating their fuel economy has become an important topic. The traditional fixed-profile test methods only indicate the effect of powertrain efficiency on fuel economy and cannot reflect the influences of control algorithms or driving behaviors on fuel consumption under real-world traffic conditions. Therefore, a data-driven simulation method for evaluating the real driving fuel economy of automated vehicles is developed. It utilizes naturalistic driving data to reconstruct test cycles. This method can inspect the performance of automated vehicle control algorithms under realistic traffic conditions in terms of fuel economy. The naturalistic driving data collected on urban expressways and freeways were used to model the longitudinal driving scenarios. Then, the fuel consumption of automated and human-driven vehicle was evaluated under the simulated scenarios via the Monte Carlo integration approach. It was found that the fuel consumption rate of the automated vehicle was 11.944 L/100 km under the car-following scenarios. The human-driven vehicle had a fuel consumption rate of 10.124 L/100 km under the same traffic conditions. The tested automated vehicle control algorithm is tuned to achieve better performance in terms of safety and travel efficiency and hence it tends to maintain a relatively steady time headway to the leading vehicle. It applies more frequent accelerating/braking cycles and higher average speed compared to typical human drivers. These characteristics lead to a higher fuel consumption rate of the automated vehicle. The presented method provides an accurate and efficient way to analyze the fuel economy performance of automated vehicles under practical conditions. This method can easily be scaled for large-scale traffic flow analyses. It can also be used to study the effects of human driving styles on fuel economy.

Fuel economy valuation and preferences of Indian two-wheeler buyers

India has experienced exponential growth in sales of two-wheelers due to their high fuel economy and easy manoeuvrability in congested traffic conditions. Understanding Indian consumers’ valuation of fuel economy while purchasing a two-wheeler is crucial to evaluate whether Indian two-wheeler buyers are myopic with regards to future fuel costs. However currently, there exists no quantification of the value that Indian two-wheeler buyers ascribe to fuel economy. We address this gap in the literature by analyzing revealed preference survey data from more than 8000 respondents across India, who purchased a new two-wheeler in 2018. Discrete choice models, including standard conditional logit and flexible mixed logit, are used to infer estimates of the discount rate that Indian consumers apply to obtain the present value of future operating cost at the time of two-wheeler purchase. The results of conditional logit indicate that the annual discount rate is below 10% for Indian two-wheeler buyers with monthly household incomes above 15,000 rupees (∼US$215 in 2018; ∼73% of the sample). Mixed logit suggests substantial heterogeneity in discount rates across respondents at a given income level. The median of the mixing distribution is close to the conditional logit estimates, which leads to a conclusion that an average Indian two-wheeler buyer ascribes a high value to future fuel cost savings. Besides, our analysis provides various insights into Indian consumers’ preferences. For instance, style/looks, fuel economy, comfort, and brand (in decreasing order) are the top four factors that influence two-wheeler purchase decisions of Indian consumers.

Design Method for Reducing AC Resistance of Traction Motor Using High Fill Factor Coil to Improve the Fuel Economy of eBus

To improve electric vehicle (EV) mileage, motors must be designed for higher power density and efficiency. Winding technology with a high fill factor decreases the motor volume by reducing the unnecessary area of the slot. A motor conductor with a large cross-sectional area generates additional losses due to ac resistance, reducing the efficiency of the motor. Traction motors designed under these conditions can adversely affect EV fuel economy. Therefore, a design method is proposed to reduce the ac resistance of a traction motor by applying winding technology with a high fill factor to increase the fuel economy of the EVs. First, the characteristics and manufacturing process of the maximum slot occupation (MSO) coil, which is a winding technology with a high fill factor, are introduced. An ac resistance reduction method for a motor using an MSO coil is then proposed. Additionally, a motor designed using the proposed method is presented, and its electrical performance is compared with that of an initial motor. Next, the effect of the fuel economy improvement of the presently designed traction motor is verified through a vehicle simulation, and the validity of this article is experimentally confirmed using this motor.

Modeling and Simulation of an Electric Vehicle with Independent Rear Motors to Estimate the Fuel Economy during EPA Drive Cycles

The “Car of the Future” project converted a 2015 rear-wheel drive (RWD) Subaru BRZ into a hybrid electric vehicle (HEV) with an intermediate milestone of a battery electric vehicle (BEV). BEV architecture required removal of the conventional powertrain components, such as internal combustion engine, transmission and differential, introduced an electric axle and battery. This intermediate BEV step provided a point at which the vehicle could be evaluated in its all electric operation with the absence of what was once critical components including its original powertrain and powertrain electronics. This step also ensures the electric components are working properly before more complexity is added to the system in building HEV. In our previous work, BEV Vehicle Technical Specifications (VTS) or requirements were developed and an electric axle was appropriately sized and selected to meet these requirements. After selecting the electrical axle with independent rear motors that will meet BEV performance requirements, Environmental Protection Agency (EPA) fuel economy rating of the BEV should be assessed. This paper presents a drive cycle analysis of the BEV vehicle using the EPA Urban Dynamometer Driving Schedule (UDDS) and Highway Fuel Economy Test (HWFET) drive cycles by means of dynamic modeling and simulation. In this study, the power required at the wheels, the efficiency of each motor and the energy required at the selected electrical axle were determined. In addition, the city, highway and combined miles per gallon equivalent (MPGe) fuel economy were determined.

Spatial competition in automobile retailing

ABSTRACT Despite a rich literature on the determinants of automobile pricing, there is relatively little formal evidence regarding the effects of spatial intrabrand competition in auto retailing. Using an extremely large sample of tax registrations in Texas (USA) for 19 of the most popular sedans, we examine how the closeness of a dealer selling the same make and model of vehicle affected the final price. We find very strong evidence that the proximity of a same-brand dealer reduces prices significantly, though we find smaller effects for the lowest priced vehicles, a result consistent with the view that such vehicles are sold essentially at cost in order to satisfy Corporate Average Fuel Economy (CAFE) standards and related fleet characteristic regulations.

A Computer Tool for Modelling CO2 Emissions in Driving Tests for Vehicles with Diesel Engines

The dynamic development of transport in recent decades reflects the level of economic development in the world. The transport sector today is one of the main barriers to the achievement of the European Union’s climate protection objectives. More and more restrictive legal regulations define permissible emission limits for the amounts of toxic substances emitted into the atmosphere. Numerical CO2 modeling tools are one way to replace costly on-road testing. Driving cycles, which are an approximation of the vehicle’s on-road operating conditions, are the basis of any vehicle approval procedure. The paper presents a computer tool that uses neural networks to simulate driving tests. Data obtained from tests on the Mercedes E350 chassis dynamometer were used for the construction of the neural model. All the collected operational parameters of the vehicle, which are the input data for the built model, were used to create simulation control runs for driving tests: Environmental Protection Agency, Supplemental Federal Test Procedure, Highway Fuel Economy Driving Schedule, Federal Test Procedure, New European Driving Cycle, Random Cycle Low, Random Cycle High, Mobile Air Conditioning Test Procedure, Common Artemis Driving Cycles, Worldwide Harmonized Light-Duty Vehicle Test Procedure. Using the developed computer simulation tool, the impact on CO2 emissions was analyzed in the context of driving tests of four types of fuels: Diesel, Fatty Acid Methyl Esters, rapeseed oil, butanol (butyl alcohol). As a result of the processing of this same computer tool, mass consumption of fuels and CO2 emissions were analyzed in driving tests for the given analyzed vehicle.

ДО ПОРІВНЯЛЬНОЇ ОЦІНКИ ПАЛИВНОЇ ЕКОНОМІЧНОСТІ АВТОМОБІЛЯ БТР-70 З РІЗНИМИ КОРОБКАМИ ПЕРЕДАЧ

The article considers the issue of choosing a gearbox for the modernization of the BTR-70 by replacing two gasoline engines with two diesels. The object of research is the fuel economy of the BTR-70 car with different gearboxes when replacing two gasoline engines with two diesels. The purpose of the work – to determine the type and gear ratio of the transmission, which provides the best fuel efficiency of the car. Research method - mathematical modeling. When replacing a gasoline engine with a diesel of a different power and a different speed range, it is necessary to determine the gear ratio so as to provide the car with the required level of speed properties in the specified operating conditions with minimal fuel consumption. Due to the fact that the modernization of the BTR-70 involves the replacement of the engine and transmission, the further search for the gearbox was carried out on the basis of analysis of existing structures by the maximum torque of the engine. A five-speed and eight-speed MAZ gearbox and a six-speed Mercedes-Benz G 85-6 / 6.7 gearbox were used for analysis. Taking into account the fact that at a given coefficient of drag  = 0.03 the car can move only in direct gear, then for all gearboxes the fuel characteristics of steady motion will be the same as the control fuel consumption, which was 30 l / 100 km. In terms of fuel consumption during the acceleration of the car and the average kilometer fuel consumption when driving on paved roads, preference should be given to a car with a Mercedes-Benz G 85-6 / 6,7 transmission and only when driving in difficult road conditions, preference should be given to the car with 8-speed MAZ-5335 transmission. KEY WORDS: CAR, ENGINE, FUEL ECONOMY, TRANSMISSION, GEAR RATING, SPEED, COMPARATIVE EVALUATION

НАПРЯМИ УДОСКОНАЛЕННЯ КОМБІНОВАНОГО МЕТОДУ РЕГУЛЮВАННЯ ПОТУЖНОСТІ ДВИГУНА З ІСКРОВИМ ЗАПАЛЮВАННЯМ

The article considers the problem of spark ignition engines low efficiency in low-load and idling modes, as well as one of the ways to solve it by improving the combined method of power control. The object of research is the influence of the power control method of spark ignition engine on fuel efficiency. The purpose of research is to improve the combined method of power control of a spark ignition engine. As a result of familiarization with the previous works which were conducted in this direction, it is established that by deactivating a group of cylinder when engine is idling or at low loads a fuel economy is improving. However, previous works has not considered a possibility of performance improving of engine with electronic control system by filling the deactivated cylinders with exhaust gases of working cylinders, heated air, or a mixture of exhaust gases and air. KEY WORDS: CYLINDER DISCONNECTION, FUEL ECONOMY, POWER ADJUSTMENT.