Facts and Arguments about Fuel Consumption

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1 Facts and Arguments about Fuel Consumption

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3 Facts and Arguments about Fuel Consumption

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5 Contents Foreword 7 Fair play 8 How fuel consumption is measured in Europe Correctly balanced 10 How the energy consumption of electric and hybrid vehicles is measured Totally standard 12 How deviations from nominal consumption values can occur Advances 14 How the automotive industry is working to develop more efficient cars People and technology 17 How driving style influences fuel consumption Worldwide harmonization? 19 What the WLTP will change and what it won t

6 6 FOREWORD

7 7 Foreword Dear Readers, We all rely on the accuracy of standardized information in everyday life. We purchase a liter of milk in the supermarket without having to check at home whether the carton really contains precisely one liter of milk. We invest in a new lightbulb and fully expect its brightness and power consumption to correspond to the information provided on the packaging. And, when it comes to the fuel consumption of motor vehicles, manufacturers are also required by law to use standardized information in all forms of advertising. However, an automobile in contrast to milk or lightbulbs is not designed for one specific application. It is precisely this freedom to determine how your own vehicle is used that makes automobiles so attractive in comparison to other means of transportation. Yet this diverse range of possible operating conditions and driving profiles cannot simply be reproduced in a defined test procedure or so-called test cycle. Nevertheless, the legally prescribed test cycles used to determine the fuel consumption of vehicles are objective, and the information they provide acts a good point of reference for car buyers. This is because the very detailed regulations governing the measurement of fuel consumption must be fulfilled in equal measure by all automotive manufacturers. In this brochure, we aim to explain how fuel consumption is measured and how the emissions regulations work in the European Union. In the process, we will also look at the special rules applying to hybrid and electric vehicles. We will then examine the most important reasons for deviations between nominal and actual consumption. Finally, we will provide suggestions on how car drivers can reduce their fuel consumption using prudent driving habits. Through this brochure, we hope to make a contribution towards a better understanding of the basic technical principles and those legal regulations that are based upon them. Dr.-Ing. Ulrich Eichhorn, Managing Director of VDA Dipl.-Ing. Bernd Mayer, Management of VDIK Dipl.-Ing. Axel Richter, Head of the Institute for Vehicle Technology, TÜV NORD

8 8 FAIR PLAY HOW FUEL CONSUMPTION IS MEASURED IN EUROPE Fair play How fuel consumption is measured in Europe The so-called manufacturer data are mandatory pieces of information prescribed by law. The ball is round and a game lasts 90 minutes. It goes without saying in the popular sport of soccer, whether in the European Championships or the German Bundesliga, the rules according to which the game is played are always the same. The set of rules, which have been modified many times since 1863, are there to ensure fairness and also mean that sporting performance in the games can be compared. The situation is similar for the official measurement of fuel consumption. The regulations that are valid today across the whole of Europe were adopted by the European Union and the UN Economic Commission for Europe (ECE) as the only binding standard for passenger cars. An important part of the process used for determining fuel consumption is the driving cycle according to which all cars are tested. It defines how far and how fast the cars should be driven and, in the case of vehicles with a manual transmission, when to shift gears. This cycle is completed by all vehicles under the supervision of independent and officially accredited testing organizations not, of course, on public roads, but instead on test stands and under uniform test conditions that have also been standardized in detail. The test cycle according to which all passenger cars from small cars through to super sports cars must be measured since 1996 is called the New European Driving Cycle (NEDC). It was already developed at the end of the 1980s, although its primary goal then was to act as a standard for the measurement of exhaust pollutants carbon monoxide, nitric oxides and unburned hydrocarbons. The NEDC consists of two parts. After a cold start of the vehicle, the first 13 minutes of the test cycle involve urban driving with multiple acceleration and braking processes, as well as phases when the vehicle comes to a complete standstill. The average speed in this part of the cycle is 18.8 km/h and corresponds to those conditions found in major cities such as Berlin or Paris during commuter traffic. An extra-urban driving cycle lasting precisely 400 seconds is then simulated in which the vehicle reaches a maximum speed of 120 km/h. The test cycle including all of the test conditions such as tires, temperature, light, etc. is standardized and mandatory across Europe. Speed curve during the European test cycle 140 Urban driving cycle Extra-urban driving cycle Speed in km/h Time in seconds Theoretical driving route 11,022 m Average speed 33.6 km/h Source: UN/ECE

9 9 In comparison to the 1/3 Euromix method in which two-thirds of the virtual route was driven at a constant speed that was valid before 1996, the regulations have been significantly tightened in the NEDC. This is because the fuel consumption of every car increases many times over during acceleration compared to driving at a constant speed. Although the accelerations are moderate after all, it must be possible for them to be completed by all vehicles the speed corridor is precisely defined. It is only permitted to deviate from the target value by a maximum of 2 km/h. Legislators have also issued precise regulations about the equipment used on the vehicle. One example is the selection of tires, the rolling resistance of which accounts for one-third of all driving resistance. It is not possible for the automotive manufacturer to positively influence the test results by using particularly narrow eco-friendly tires. Instead, the widest tires that are permitted for use with the vehicle must always generally be used. However, when there are four or more tire variants, the second-widest tire is permitted. The daytime running light must also be switched on during the test. In contrast, special features that are not offered as standard in all vehicles such as air-conditioning systems are not taken into account. The test cycle is monitored by independent and officially accredited testing organizations. It is important that the test carried out in the laboratory takes account of the vehicle mass or in other words its weight. This is because the car s wheels drive a roller on the test stand and in doing so the vehicle can cover kilometer after kilometer while remaining stationary. The roller needs to be artificially slowed down in order to simulate the forces that a car is exposed to when propelling itself along the road: above all, its own inertia. In the laboratory, this is achieved using a centrifugal mass a sort of artificial weight. In general, no real masses are used any more today; instead, the roller runs on an adjustable electric brake, which is used to simulate resistance. Another factor that is prescribed in the test is the temperature at which the test must be completed between 20 and 30 C. The car s engine is not permitted to be warmed up, but rather it must also be conditioned over many hours in a temperaturecontrolled room until the temperature of the motor oil and cooling water only deviate from the ambient temperature by a maximum of 2 C. This is not only important for the fuel consumption measurements, but also for the measurement of pollutant emissions. The reason is that modern catalytic converters make more than 95 percent of all pollutants harmless, but in order to do so they must first reach an operating temperature of several hundred degrees. So as not to falsify the measurement results, the test is, therefore, always started with a cold engine. The fuel consumption during the test is incidentally measured by an independent technical service provider, e.g., TÜV. This ensures all legal regulations are observed and that the determined fuel consumption is correct. The often-used phrase manufacturer data is thus misleading because manufacturers are only permitted to refer to the certified consumption values in their advertising. Despite the continuously high level of criticism levied at individual test conditions, the NEDC has fulfilled its objective of establishing a fair set of rules that neither favors nor disadvantages individual manufacturers in a competitive environment. Although the test cycle was originally developed for Europe, it has also become established in other regions. China, which has the largest passenger-car market in the world, Argentina, Australia and South Africa have also adopted the European driving cycle into their own legislation.

10 10 CORRECTLY BALANCED HOW THE ENERGY CONSUMPTION OF ELECTRIC AND HYBRID VEHICLES IS MEASURED Correctly balanced How the energy consumption of electric and hybrid vehicles is measured The fuel consumption of electric and hybrid vehicles has also been standardized across Europe. The amount of fuel consumed by a car is given in liters per 100 kilometers. However, this is not considered a universal law as the Americans prefer to use the distance covered given in miles per gallon. Since it has become generally accepted that anthropogenic CO 2 emissions (those produced by human activity) contribute to climate change, one new unit of measurement used for CO 2 emissions is grams of CO 2 per kilometer. All vehicles up to a total weight of 3.5 tons, irrespective of the vehicle category, complete the same test cycle under identical test conditions. In the case of vehicles with conventional drive systems, the measurement values are taken on the exhaust test stand and then converted into units per kilometer. This process is set to become a little more complicated in future, as in addition to a combustion engine, an increasing number of cars have an additional electric drive system or can even be driven exclusively using electrical power. It would thus no longer be sensible to test these types of vehicles using the conventional process. Legislators recognized this trend at an early stage. ECE Regulation 101 differentiates between three categories of vehicle to which specific testing regulations apply, depending on the degree of electrification: Vehicles exclusively powered by combustion engines Vehicles exclusively powered by electric motors Hybrid vehicles that use both types of drive system If a vehicle is being powered solely by electric power, it does not emit any CO 2 emissions. Correspondingly, the route covered solely using electric power is rated as 0 g/km CO 2 irrespective of whether the vehicle has actually been charged using green electricity sourced from renewable energies. This view taken by legislators can be understood against the background of the European CO 2 emission regime. The European Union consciously decided to clearly differentiate between the supply and use of energy. Power plant operators who want to produce electricity using fossil fuels such as coal or natural gas must purchase emissions certificates in order to be permitted to expel a certain amount of carbon dioxide. They can purchase certificates from other market participants, but not increase the total volume available on the market. It is therefore impossible for any additional electricity consumption due to electrically powered vehicles to lead to an increase in the overall CO 2 emissions in Europe. Furthermore, it has become apparent that most automotive manufacturers already offer their customers a green energy contract with their electric car. Nevertheless, it is still sensible to determine the fuel consumption or in this case the electricity consumption of purely electric cars. This is because it directly and indirectly influences the cost to the consumer directly via the price of electricity and indirectly because electric cars with greater efficiency either require smaller batteries, which thus reduces the purchasing price, or have a larger range and are more versatile. In order to determine the fuel consumption, which is given in kilowatt-hours per 100 kilometers (kwh/100 km), the same driving cycle (NEDC) used for vehicles with a combustion engine is completed this is logical because electric cars are, after all, driven in the same traffic conditions. Purely electric cars complete the test cycle twice with a fully charged battery. The vehicle must then be connected to the electricity grid again within 30 minutes. During the charging process, an energy measurement device a sort of electricity meter is connected between the mains socket and the charging cable. It counts the watt hours consumed, which are then subsequently divided by the number of kilometers completed on the test stand. The result in Wh/km can then easily be converted into

11 11 kwh/100 km. A special feature of this process is that power lost during the charging process is also recorded. Every battery heats up when it is being charged due to the electromagnetic processes inside it everyone is familiar with this from cell phones. A modern battery management system can, however, reduce this loss of power considerably. The situation becomes significantly more complicated when dealing with hybrid vehicles that have both an electric motor and a combustion engine. The test process differentiates between hybrid vehicles that can be externally charged (plug-in hybrids) and those in which the battery is charged solely by the vehicle itself for example through the recovery of braking energy. Plug-in hybrids are generally tested twice: once with a fully charged battery and then again with a discharged battery. Therefore, the vehicle initially completes the NEDC with a full battery and continues to do so for as long as possible until the battery has been completely discharged. If the electrical power is sufficient to achieve the acceleration processes and the maximum speed of 120 km/h required in the test cycle, the car is exclusively powered in this section of the test by the electric motor and its emissions are rated as 0 g/km CO 2. In the second section of the test, the plug-in hybrid completes the test cycle again with a discharged battery, meaning that the required power is provided by the combustion engine. The emissions value is once again calculated in g/km CO 2. Finally, a formula is used to combine the two values that takes into account the separately measured electric driving range. Without going into too much detail about the mathematical formula used, one thing is clear: The further a vehicle can travel with a fully charged battery, the lower the overall CO 2 emissions value. This is logical because, in normal operation, plug-in hybrids with a high electric driving range can be used completely without the need for the combustion engine more often than plug-in vehicles with a smaller battery. Larger vehicles or sport vehicles can thus achieve double-digit CO 2 emission values as plug-in hybrids. Hybrid vehicles that cannot be externally charged have lower electric driving ranges, which rarely exceed two kilometers even with a fully charged battery. The legislators have thus stipulated a test for these hybrid vehicles that is very similar to that used for vehicles with just a combustion engine. However, the battery charge must still be taken into consideration. In addition to the CO 2 emissions, the charge level of the battery is thus determined and the emissions value is corrected accordingly. In the case of both electric and hybrid vehicles, it holds that the values determined using the legally prescribed tests indicate the efficiency of the drive systems under the given test conditions, and thus make an impartial comparison possible. Technology used in a plug-in vehicle

12 12 TOTALLY STANDARD HOW DEVIATIONS FROM NOMINAL CONSUMPTION VALUES CAN OCCUR Totally standard How deviations from nominal consumption values can occur The NEDC takes no account of air-conditioning systems, heated seats or heated rear windows, nighttime driving, hills, climatic zones, seasons or curves. The nominal fuel consumption for the most-efficient diesel version of the best-selling car model in Germany is 3.2 l/100 km with 85 g/km CO 2. It offers an extremely comfortable ride for its five passengers and the 81 kw (110 PS) engine delivers a good amount of power. Five-star safety features are standard, as well as an air-conditioning system. Yet the fuel consumption of this model will generally be higher in normal daily use and there are a whole series of good reasons why this is the case. The NEDC used for determining CO 2 emissions does take account of some significant factors that have an influence on the fuel consumption of a passenger car on public roads. It demonstrates, above all, how economical the vehicle is in comparison to other vehicles under identical test conditions. All losses that occur when transferring the engine torque to the wheels for example, through the transmission are also taken into account. But not all conditions experienced under real traffic conditions can be tested in the laboratory. For example, the legally prescribed test does not take into account the topography the car is always driven at one level. However, driving uphill requires the car to additionally overcome the forces of gravity. It is also not possible to simulate curves on most test stands, which is why the regulations prescribe that the vehicle is always driven in a straight line. In reality, driving around a curve always requires a little more energy because the power steering needs to be operated and the tires have to overcome greater deformation forces. Even more important when it comes to actual fuel consumption levels is the fact that the comparability strived for by the legislators can only be achieved by imposing a standardized speed profile. Those who like to drive in a sporty manner or make the most of the speed limits permitted on motorways need to accelerate more frequently. The energy required for these processes can only be taken from the fuel. The time of the day and the weather conditions can also differ for every single journey and cannot be correspondingly reproduced on the test stand. Therefore, the main headlights are left switched off during the test just like other electrical consumers in the vehicle such as the rear window heating or heated seats. The lower the nominal consumption, the higher the potential deviation even if the CO 2 emissions are reduced in absolute terms. Influences on actual fuel consumption Consumption Topography Air-conditioning / heating NEDC value Sporty Influence of the driving style Economical Influences Source: VDA

13 13 Technical influences on fuel consumption Energy conversion Mechanical energy losses Engine: Converting chemical energy into mechanical energy Powertrain: Transmission, tires, wheel bearings, power-steering pump Engine: Friction, combustion process, charge exchange process Overcoming external driving resistances Weight Air resistance Topography Comfort and other significant technical influences Air-conditioning, cooling system, electronics Air-conditioning systems have a particularly major influence on actual fuel consumption and can temporarily cause additional consumption of up to 2 l/100 km. The length of time the air-conditioning is in use strongly depends on local climatic conditions yet the European driving cycle is valid in Oslo just the same as it is in Athens. All passenger cars must also complete the test cycle using summer tires for similar reasons. Winter tires naturally have a higher rolling resistance because the tread is larger and deforms less easily. They thus also increase fuel consumption significantly, by up to 0.5 l/100 km. For the reasons stated above, actual fuel consumption is generally higher than the legally prescribed nominal values. In test drives completed using a total of 563 different car models, the magazine auto motor und sport recorded the following results for their own fuel consumption cycles in which the vehicles were driven as economically as possible: The fuel consumption for 53 percent of all models was higher than the corresponding NEDC value. Seven percent had identical fuel consumption to the NEDC value. And in almost 40 percent of all models, the fuel consumption values were lower than the NEDC value (see chart on p. 18). Would it not be possible for automotive manufacturers to take this into account in their advertising and quote a corresponding of up to value? As customer-friendly as it would seem to be to supplement data measured for the CO 2 standard with additional information, the law does not permit this to happen in order to avoid any misuse. All manufacturers are required, and also only permitted, to publish the values determined in the official test cycle and in precisely the sequence stipulated. All models must also be allocated an efficiency class based on this data. Manufacturers are only permitted to communicate fuel consumption data using the prescribed standard. Nothing more and nothing less. It would, in any case, prove difficult to determine the typical level of fuel consumption in real life. This is particularly true for plug-in hybrids. Drivers who commute just 20 kilometers and regularly charge their battery will almost never use the combustion engine and will remain significantly below the official nominal values. In contrast, drivers who use a plug-in hybrid for long work trips or vacations can exceed the nominal values by several hundred percent because the portion of the overall driving route covered using electric power will be low. Does this then mean that publishing the nominal fuel consumption is a waste of time? Not at all, because despite these unavoidable deviations from reality, it still enables different drive systems to be compared. An engine-transmission combination that consumes 10 percent less fuel than another on the test stand will generally also maintain this advantage at approximately the same level in practice. The determination of CO 2 emission values also enables different drive system concepts to be compared to one another. When considering fuel consumption purely based on volume in l/100 km, as was commonly done in the past, the fact that the carbon density in diesel is around 15 percent higher than in gasoline wasn t taken into account or in other words: when the same amount of fuel is consumed by volume, a gasoline engine would be more environmentally friendly than a diesel engine. It will be more important than ever in future for car buyers to select a drive system that fits their personal daily and yearly driving profile. Automotive manufacturers are geared to fulfilling a wide variety of customer wishes. Economic diesel and gasoline engines, natural gas and hybrid drives through to purely electric vehicles with fuel cells or batteries for short-distance operation are just some of the options that will be available for customers to choose from to match their own personal energy savings program in the future.

14 14 ADVANCES HOW THE AUTOMOTIVE INDUSTRY IS WORKING TO DEVELOP MORE EFFICIENT CARS Advances How the automotive industry is working to develop more efficient cars Modern cars are safer, cleaner, longer lasting, more comfortable and, at the same time, more economical. Anybody walking in the wrong direction on an escalator really has to struggle to reach their destination. This is exactly what the automotive industry is faced with when trying to reduce fuel consumption. The figurative escalator in this case is the list of all those factors that actually cause modern cars to consume lots more fuel. Ever-greater demands from customers and legislators have also been added to this list in the last few decades: Modern cars are now safer than ever before: not only are driver assistance systems able to nearly always keep the vehicle stable on the road but are also able to warn against accidents and automatically bring the vehicle to an emergency stop. And if an accident nevertheless occurs, passengers are protected by airbags. The number of road fatalities thus fell by the end of 2013 to less than 3,400 people per year in Germany. This is the lowest level since All of these safety systems have led to a significant increase in vehicle weight. The pollutants in exhaust emissions have depending on the type of pollutant been reduced by up to 99 percent. Exhaust purification systems not only add significant additional weight, but also in some cases directly result in higher fuel consumption. For example, the regeneration of diesel particulate filters in urban traffic requires the injection of additional fuel. Modern cars are longer lasting, more robust, more comfortable and more oriented towards the individual requirements of customers. This is reflected in the broad range of vehicle categories that stretches today from small cars through to family-friendly vans. This has led to an increase in the volume, weight and performance of vehicles, as well as to greater fuel consumption. Development of traffic volume and CO 2 emissions in Germany in % % % CO 2 emissions Traffic volume Source: VDA

15 15 Despite these counteractive effects, the average fuel consumption across the total fleet of passenger cars in Germany fell between 1991 and 2012, by 9.2 liters to 7.3 l/100 km which corresponds to a reduction of around 20 percent in two decades. This development is even more apparent if only new vehicles are considered: These vehicles experienced a reduction of 35 percent over the same period. At the beginning of 2014, there were 1,600 models available on the German market that already performed better than the fleet average CO 2 emission target of 130 g/km set for And 50 models already performed better than the fleet average CO 2 emission target of 95 g/km set for CO 2 emissions are falling despite the increased volume of traffic thanks to research and development. Nevertheless, there is still scope for further improvement on existing technical advances. This is why more than two-thirds of the money invested by manufacturers and the supplier industry into research and development is focused on achieving higher efficiency. The optimization of conventional combustion engines currently receives a lot of attention because, according to a forecast by the renowned market research institute IHS, they will still account for around 94 percent of all passenger car and light commercial vehicle drive systems in A particularly significant development is the recent trend towards downsizing, meaning engines that can deliver greater power with a small engine capacity and thus frequently work at more economical operating points. To ensure that these operating points can also be utilized in practice, modern transmissions with up to nine gears have been developed that deliver very large differences in the gear ratio between the lowest and highest gears. In parallel to the necessary optimization of traditional drive systems, the automotive industry has introduced a wide variety of alternative drive systems onto our roads in recent years: Natural gas drives that emit around 25 percent less CO 2 with an identical energy output due to the chemical properties of the natural gas Electric vehicles that produce no local emissions and can draw their electricity from renewable energy sources in combination with corresponding supply contracts Different types of hybrid vehicles that reduce fuel consumption by up to 25 percent or can even be operated solely from electrical energy for daily commutes as plug-in hybrids Hydrogen vehicles that draw their energy from a fuel cell, only emit water vapor and can cover large distances using hydrogen produced from renewable sources With the exception of fuel cells, all of these drive systems are already available for normal customers to purchase today. Development of average fuel consumption across the total fleet of passenger cars in Germany Average fuel consumption in l/100 km l Source: DIW

16 16 ADVANCES HOW THE AUTOMOTIVE INDUSTRY IS WORKING TO DEVELOP MORE EFFICIENT CARS Yet it is not only efficient drive systems that are improving the energy balance in modern cars. Innovations that enable the economic use of energy can be found throughout the whole vehicle: The automotive industry has managed to stop the spiraling increase in car weight. The use of high-strength steels and aluminum, as well as an increasing amount of composite materials such as CRP, have ensured that the weight of new vehicle models has generally not increased despite improved safety systems and comfort features. One rule of thumb here is that a reduction in weight of 100 kg will result in a reduction in fuel consumption of up to 0.3l/100 km. Low rolling resistance tires can reduce fuel consumption by around 2 percent. Any drawbacks in terms of safety for example, when braking have been eliminated due to modern high-tech rubber compounds. The aerodynamic drag of the entire vehicle has been systematically reduced. In this process, engineers have not only focused on the design of the body but also the underbody, wheel housings and radiator. The efficiency of the electrical consumers in vehicles has been systematically improved to achieve lower fuel consumption starting with efficient electricity generation on board and covering the optimization of all electrical consumers in vehicles, such as the headlights whose energy consumption can be significantly reduced using modern LED technology. This example also demonstrates that the automotive industry is not just concentrating on minimizing consumption during the test cycle, because the headlights remain turned off during the official test. The focus has also been placed on optimizing mechanical auxiliaries (for example, the air-conditioning compressor). Despite the fact that the air-conditioning system is not in operation during the NEDC, efficient air-conditioning systems can significantly limit any additional fuel consumption, especially in the summer. Automotive manufacturers and supplier companies are carrying out intensive research into other systems to help car drivers save fuel in real traffic conditions. For example, future navigation systems will communicate with engine electronics and adaptive cruise control systems. Obstacles such as steep slopes or entering city limits will be identified before the driver sees them with his own eyes. This will enable, for example, hybrid vehicles to utilize the electrical energy stored in the battery in such a way as to keep the total fuel consumption as low as possible. Cooperative driver-assistance systems go even one step further by enabling vehicles to also warn each other about temporary obstacles, such as an oil spill on the road. A number of other technologies are still at the advanced development or even research stages. The industry is currently working on utilizing the heat from combustion engines not only to heat the interior of the vehicle, but also to recover electrical energy. Onboard electrical systems can be partially switched to higher voltages (48 volts), while new composite panels made out of steel and CRP can save additional weight. Car lights of the future could also be produced using particularly efficient laser diodes. These are just some examples to demonstrate that there is no loss of momentum in current technological progress.

17 17 People and technology How driving style influences fuel consumption Technology can be standardized but thankfully people cannot. While standardized test cycles such as the NEDC enable comparisons to be made between different models at a technical level, the driver s personal driving style is not included in this evaluation. Yet one thing remains certain: It has a significant influence on actual fuel consumption in real road traffic. The greatest influence on fuel consumption is sitting behind the steering wheel. There are a whole series of factors that can push up the fuel consumption of a car given the current state of technology. Anyone who is aware of these factors can counteract them and drive their car particularly economically. This personal energy savings program could include the following components: 1. Forward-thinking driving Every car consumes the least amount of fuel when it is driven at a constant speed it will only require the energy that is lost due to the rolling resistance of the tires and aerodynamic drag. In other words: The less often and the less severely you accelerate, the less you will need to refill the fuel tank. A forwardthinking driving style thus has the double benefit of delivering lower fuel costs and increased safety. Incidentally, this also applies to hybrid vehicles: Although they can recover some of the energy that is otherwise lost due to braking, this process does not occur without the loss of some energy. 2. Shifting to a higher gear earlier Modern combustion engines with a turbocharger can deliver very high torque at low engine speeds and thus provide good pulling power. When the tachometer reaches 2,000 rpm, it is high time to shift up to the next-highest gear. Modern cars generally indicate the optimum time for shifting gears on the instrument cluster. Those who don t want to constantly keep an eye on the tachometer would be best delegating the task of shifting gears for example to a double-clutch transmission or a stepped automatic transmission. 3. Avoid driving short distances A car consumes a particularly high amount of fuel directly after a cold start the colder the engine, the more fuel is consumed. This is caused by the lubricants, such as the engine and transmission oils, which have a high viscosity at low temperatures. The high level of friction between all of the moving parts causes a significant increase Impact of gear selection on fuel consumption Fuel consumption in l/100km Speed in km/h 1st gear 2nd gear 3rd gear 4th gear 5th gear 6th gear Source: VDA

18 18 PEOPLE AND TECHNOLOGY HOW DRIVING STYLE INFLUENCES FUEL CONSUMPTION in fuel consumption over the first few kilometers. When the temperature is above zero degrees Celsius, a constant average fuel consumption is only achieved after around seven kilometers. Therefore, those who avoid driving short distances, for example, by combining journeys or by switching instead to a bicycle will certainly be making a contribution to preserving the environment. 4. Use smooth-running oils Synthetic engine oils are not quite so viscous at lower temperatures and thus reduce fuel consumption particularly after a cold start by up to 5 percent. This is why when it comes to motor oil, don t try to cut costs in the wrong places. 5. Check the tire pressure The tires are constantly deformed during a journey. The lower the internal pressure, the more the tire flexes and uses more energy. The influence on the total fuel consumption can be enormous particularly at low speeds. It is thus advisable to check the air pressure in the tires at least once a month at the filling station and refill them if necessary. Incidentally, fuel-saving professionals always use the tire pressure that is recommended for when the car is fully laden. 6. Leave unnecessary items at home Engineers working for automotive manufacturers wrestle with every single kilo, because a lighter car will consume less fuel during every acceleration. Car drivers should, therefore, follow the lead set by car designers. This is also true for add-on accessories and superstructures that are only sometimes required and thus negatively influence the vehicle s aerodynamics. A roof box, for example, can increase fuel consumption by up to 1 l/100 km at a speed of 100 km/h. 7. Use climate control systems moderately The air-conditioning system is the most important additional consumer of electricity in the car in the summer. In extreme cases, when driving very slowly in urban areas and with an outside temperature of more than 30 degrees Celsius, it can sometimes cause additional fuel consumption of up to 2 l/100 km. Therefore, if the interior of the vehicle has become very hot it is a good idea to drive the first few meters with the air-conditioning turned off and the windows open so that the very warm air can firstly escape. All of the windows should then be closed and the air-conditioning system switched on although for the first few minutes only in air recirculation mode. An increasing number of manufacturers are offering automatic climate control systems with an eco button. This is sufficient during moderate temperatures to keep the air humidity and temperature in the interior of the vehicle at a pleasant level. Technology is thus providing people or in this case drivers with an increasing level of support. Nevertheless, one thing will still remain true in the future: Everyone is able to choose their driving style themselves. Deviations in fuel consumption attributed to a more sensible driving style in different vehicle models Deviation in l Deviation in l Deviation in % Data: AMS; Graphic: VDA

19 19 Worldwide harmonization? What the WLTP will change and what it won t Rules are made by people and are thus not written in stone. The decision taken by European legislators to use the NEDC test cycle to measure CO 2 emissions levels and fuel consumption is one such rule. The cycle was developed for Europe. In other regions of the world, different traffic conditions prevail and thus other consumption measurement cycles are (still) valid. For example, although India has adopted the NEDC, it has lowered the maximum speed to 90 km/h. Anybody who has ever driven a car in India will know that even a speed of 90 km/h will rarely be achieved. The extra-urban driving section of the Japanese IC-08 cycle is, on the other hand, very small, which is consistent with a country dominated by major cities with millions of inhabitants; whereas in the USA, the proportion of very slow speeds is low, although vehicles brake more often than in Europe. Despite these justifiable differences, the UN Commission has been striving to introduce a standardized worldwide test cycle for passenger cars and light commercial vehicles for a long time a thoroughly reasonable measure in this era of globalization, which will not only open the way for a uniform approval process around the world, but also the comparison of products on a global scale. The speed profile for the new test cycle has been defined the test conditions for carrying out the procedures are still being discussed. The WLTP ( Worldwide Harmonized Light Duty Test Procedure ) standard has already been defined to a large extent by an expert commission, even if some of the test conditions for carrying out the procedures are still being discussed. The European Commission is planning to introduce the WLTP from 2017/2018. However, it is first necessary to clarify all outstanding issues so that this new test procedure will be 100 percent applicable. The WLTP driving cycle was generated using real driving data collected around the world and thus represents an average global car journey. In its current version, the WLTP differentiates between the four speed classes low, middle, high and The US and the European test cycles differ considerably Speed in km/h FTP 75 (USA) Time in s Speed in km/h NEDC (EU, China) Time in s Graphic: EPA, UN/ECE

20 20 WORLDWIDE HARMONIZATION? WHAT THE WLTP WILL CHANGE AND WHAT IT WON T The WLTP represents one average car journey worldwide. It can thus only generate one standard value. extra high whereby the maximum speed is 131 km/h. Overall, this worldwide test cycle has a higher average speed and more dynamic accelerations, but also fewer traffic light phases in which the car comes to a standstill. The test conditions have also been fundamentally revised for the WLTP. The primary goal during the revision was, as far as possible, to provide a representative depiction of global traffic conditions. The first tests completed by different automotive manufacturers and independent laboratories indicate that the determination of emission data according to the WLTP will lead to higher CO 2 and fuel consumption values for the same vehicle. Yet even the WLTP will only be able to provide one standard value that is designed to be globally representative but will not be able to cater for the entire range of different variations. Traffic conditions and also weather conditions will continue to differ across the various regions of the world in the future and thus so will actual fuel consumption values. Furthermore, some automotive producing countries such as the USA have already spoken out against the rapid introduction of the new test cycle. It must therefore be assumed that the following will continue to be true after the introduction of the WLTP: A test cycle only represents an objective standard for the comparison of technical products. Nothing more but also nothing less. Irrespective of which test cycle is currently valid, the automotive industry and its suppliers will also continue to work intensively on reducing CO 2 emissions in the future both in the laboratory and, above all, in real traffic conditions. Speed profile for the future WLTP world cycle Speed in km/h Low Middle High Extra-High Time in s WLTP NEDC Source: UN/ECE New WLTP cycle WLTP NEDC Start temperature Cold Cold Cycle time 30 min. 20 min. Proportion standing still 13 % 25 % Distance km 11 km Speed average: 46.6 km/h maximum: 131 km/h average: 34 km/h maximum: 120 km/h Driving power average: 7 kw maximum: 47 kw average: 4 kw maximum: 34 kw Influence of optional equipment and air-conditioning Optional equipment will be taken into account in terms of its weight, aerodynamics and the power consumption of any onboard electrical systems (no-load current). No air-conditioning system. Not currently taken into account. Source: UN/ECE

21 IMPRINT 21 Imprint Publisher Contact VDA, VDIK, TÜV NORD VDA Verband der Automobilindustrie e. V. (German Association of the Automotive Industry) Behrenstr Berlin Copyright Verband der Automobilindustrie e. V. (VDA) 2014

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