Browse Topic: Emissions certification
The battery of a vehicle with an electrified powertrain (Hybrid Electric Vehicle or Battery Electric Vehicle), is required to operate with highly dynamic power outputs, both for charging and discharging operation. Consequently, the battery current varies within an extensive range during operation and the battery temperature also changes. In some cases, the relationship between the current flow and the change in the electrical energy stored seems to be affected by inefficiencies, in literature described as current losses, and nonlinearities, typically associated with the complex chemical and physical processes taking place in the battery. When calculating the vehicle electrical energy consumption over a trip, the change in the electrical energy stored at vehicle-level has to be taken into account. This quantity, what we could call the vehicle electricity balance, is typically obtained through a time-based integration of the battery current of all the vehicle batteries during operation. In such cases, the charge storage efficiency is often assumed unitary, meaning that the conduction of electrical charges on the battery cables corresponds to an equal amount of charge being stored/released in/from the battery; this is also the case for the official energy consumption/CO2 emissions certification procedure for light-duty vehicles. The Joint Research Centre has collected experimental data from different vehicles with electrified powertrains concerning the electrical energy use and the State Of Charge (SOC) of the traction battery communicated from the vehicle; the latter was used as a reference to quantify the actual vehicle electricity balance from a trip or driving cycle. This work investigates the accuracy of the simple Coulomb Counting method with unitary charge transfer efficiency for the quantification of the vehicle electricity balance. The simple-Coulomb-Counting-based and the vehicle-SOC-based estimations of the vehicle electricity balance are compared and presented; the significant deviations encountered for some vehicles, which might affect the certified CO2 emissions and electrical energy consumption values, are discussed. Finally, an improved version of the Coulomb Counting method, which uses charge correction factors derived from experimental data to improve the estimation, is presented.
The automotive industry is gearing up to meet the accelerated emission compliance changes posed by the government. This transition to eco-friendly system would also necessitate an automotive engineer to retain the engine packaging as compact and simple as possible. The packaging layout considered should not be at the expense of deteriorating engine performance. The work started with concept level layout development, with the aim of having simplified system with minimum number of components. The engine on which the work was carried out was 4cylinder 3Liter with OHC configuration A number of layouts were developed which included gear type, belt drive and integrated shaft arrangement for driving FIP. Each of these concepts were brainstormed with its advantages and disadvantages, based on which two concepts were initially proposed for driving FIP system (i) Front Driven FIP (ii) Rear Driven FIP. The difference between the two layouts was that in the latter case the FIP system was directly driven through exhaust camshaft with gear type arrangement. For the above two proposed layouts, dynamic evaluation was done up-to max intermittent speed of engine by modeling complete valve-train system along with chain drive in AVL Excite timing drive. The Excite timing drive model dynamic results showed that with the rear layout FIP system, the valve-train along with chain drive system was getting heavily loaded demanding more robust design leading to an unintentional increase in system mass. For further visualization of the two layouts, engine level testing was done by developing proto parts for both the concepts and the conclusive results were found to be in-line with the simulation results.
The forecast scenarios regarding the environmental pollution raises a question whether the current vehicle emission certification is reliable enough to assure fleet agreement with the legal limits. Type approval tests have been performed on chassis dynamometer in order to evaluate the emission factors and fuel consumption for passenger cars. Standardized procedures such as the FTP-75 proposed in the United States (currently incorporated in the Brazilian legislation) and the Worldwide harmonized Light vehicles Test Cycle (WLTC), a transient driving cycle model designed by the European Union to overcome the shortcomings of the New European Driving Cycle (NEDC), are discussed in this paper. Both cycles were performed in a chassis dynamometer with a flex-fuel passenger car running on ethanol blend (E92W08). The driver, vehicle and fuel were kept constant so the comparison between the cycles would not be compromised. The vehicle chosen was a 1.4 dm3 displaced volume FIAT sedan with maximum power of 60 kW at 5500 rpm and maximum torque of 122 Nm at 2250 rpm. The cycle dynamics and the engine operation points were assessed in this paper. The five points estimated as the most representative of both tests were selected for steady-state investigations conducted using hydrous-ethanol (E97W03), which is the ethanol blend available in Brazilian fuel stations. These points were evaluated in terms of fuel consumption and air excess factor. The results showed that the FTP-75 demanded greater average and maximum acceleration values, implying on more aggressive driving conditions. The WLTC presented a more homogeneous acceleration per speed diagram, providing higher average speed and speed standard deviation (e.g. more transient conditions) which is more like the real drive conditions. It could be seen that the WLTC covers a wider range of engine operation conditions holding more dispersed points than the FTP-75. In addition, the WLTC contained points with higher load, which made the results for fuel consumption to be higher compared to FTP-75. The engine operation points provided by the FTP-75 were excessively condensed. Therefore, it could be concluded that the FTP-75 can be a predictable test with repeated points of operation. The WLTC does not have sufficient number of trips in its schedule, which is different from the behavior expected in real-world driving conditions. Also, it could be observed that depending on the test specifications the driver can largely influence the performance of the vehicle.
Partially premixed combustion (PPC) has shown to produce high gross indicated efficiencies while yielding lower pollutant emissions, such as oxides of nitrogen and soot, than conventional diesel combustion. Gasoline fuels with a research octane number (RON) of 60-70 have been proposed as optimal for PPC as they balance the trade-off between ensuring good combustion stability at low engine loads and avoiding excessive peak pressure rise rates at high loads. However, measures have to be taken when optimizing the engine operating parameters to avoid soot emissions. In contrast, methanol has a much lower propensity for soot formation. However, due to a higher RON of methanol the required intake temperature is higher for the same engine compression ratio to ensure auto-ignition at an appropriate timing. Increasing the compression ratio allows a lower intake temperature and improves combustion stability as well as engine brake efficiency. Nevertheless, a higher compression ratio generally increases in-cylinder heat losses and peak pressure. These effects were investigated in a simulation study, which combined 0-D and 1-D models, of a multi-cylinder heavy-duty Scania D13 engine operated in PPC mode and running on methanol. Engine experiments from a single-cylinder engine at different compression ratios were used to validate the simulation models. The optimal compression ratio from a brake efficiency perspective was found for four operating conditions from the 12 mode non-idle European stationary cycle supplemental emissions test points. This compression ratio was then used for optimizing key engine parameters. The results showed that a 21.6:1 compression ratio was optimal instead of the original 17.3:1 compression ratio. Especially at lower engine loads, a significant increase in brake efficiency was found. The main reason was a lower intake temperature which increased the average ratio of specific heats and allowed for a lower boost pressure.
Climate change is primary driver in the current discussions on CO2 reduction in the automotive industry. Current Type approval emissions tests (BS III, BS IV) covers only tailpipe emissions, however the emissions produced in upstream and downstream processes (e.g. raw material sourcing, manufacturing, transportation, vehicle usage, recycle phases) are not considered in the evaluation. The objective of this project is to assess the environmental impact of the product considering all stages of the life cycle, understand the real opportunities to reduce environmental impact across the product life cycle. As a part of environmental sustainability journey in business value chain, lifecycle assessment (LCA) technique helps to understand the environmental impact categories. To measure overall impact, a cradle to grave approach helps to assess entire life cycle impact throughout various stages. LCA is a technique to assess environmental impacts associated with all the stages of a product's life from raw material extraction through materials processing, manufacture, distribution, use, repair and maintenance, disposal or recycling. A study was conducted on a passenger vehicle for life cycle assessment as per ISO 14040 and ISO 14044. Data has been collected from various sources for this study. This technique evaluates impact of all the stages in manufacturing a vehicle till vehicle reached its end of life. This analysis helps conduct environmental cost benefit analysis and comparison between various choices for existing materials processes, product. This study gave a comparative analysis of various material choices and processes available to make same components and assemblies by analyzing material composition for complete vehicle. Study for complete life cycle with service life use of 300,000 km, maximum impacts like global warming potential, human toxicity, eutrophication and acidification potential occurred during the use phase followed by manufacturing phase and end of life phase. Data for actual environment impact for processes and material for product under study need to be considered from global data base where actual data is not available. This study helped to assess extent of various environmental impact like GWP, water consumption, acidification potential, ozone depleting potential etc., with only soft data collected from various internal stakeholders without making actual parts or vehicles. LCA helps in design improvements, right material selection, high impact processed to be focused upon. Thus, life cycle assessment can be used as an effective tool to provide sound knowledge on environmental impacts of product and help in environmentally sound decision making.
This article focuses on a comparative research of the emissions discharged from four vehicles equipped with SI engines, which comply with different emission control systems (Euro 6, Euro 5, and Euro 3). The vehicles used for this work were installed with two different fuel injection technologies (direct injection and port fuel injection) and were operated with three different types of fuels (RON 95, M15, and E10). The tests were performed at the Joint Research Center (JRC) in Ispra using a state-of-the-art emissions test facility according to the European emissions legislation. The test bench included a chassis dynamometer and two different driving cycles were used: NEDC and US06. The main conclusions observed by this article are: (1) Emissions levels from vehicles fueled with M15 are similar to or lower than from those fueled with RON95. (2) Using M15 has the potential to decrease carbon dioxide emissions and to save fuel on an energetic basis. (3) PM emissions are lower for gasoline/alcoholic fuels. (4) No statistically significant effects on carbonyl emissions were found with M15.
In order to meet the worldwide increasingly stringent particulate matter (PM) and particulate number (PN) emission limits, the diesel particulate filter (DPF) is widely used today and has been considered to be an indispensable feature of modern diesel engines. To estimate the soot loading amount in the DPF accurately and in real-time is a key function of realizing systematic and efficient applications of diesel engines, as starting the thermal regeneration of DPF too early or too late will lead to either fuel economy penalty or system reliability issues. In this work, an open-loop and on-line approach to estimating the DPF soot loading on the basis of soot mass balance is developed and experimentally investigated, through establishing and combining prediction models of the NOx and soot emissions out of the engine and a model of the catalytic soot oxidation characteristics of passive regeneration in the DPF. The emission testing results under the New European Driving Cycle (NEDC) show that the prediction errors of the engine-out NOx and soot emission models are 5.1% and 3.9%, respectively. Tests and validations of the soot mass loading model are carried out under on-vehicle driving. The experimental results show that the maximum estimation error of the model is 0.48g/L and the average error is 0.17g/L. It shows that the model estimation error is less than 6%, which is conducive to promoting safe and reliable DPF regeneration and contributes to the DPF management and applications in real-world operation.
This document covers the requirements for transceiver qualification. Requirements stated in this document will provide a minimum standard level of performance for the CAN transceiver in the IC to which all compatible transceivers shall be designed. No other features in the IC are tested or qualified as part of this recommended practice. This will assure robust serial data communication among all connected devices, regardless of supplier. The goal of SAE J2962-2 is to commonize approval processes of CAN transceivers across OEMs. The intended audience includes, but is not limited to, CAN transceiver suppliers, component release engineers, and vehicle system engineers.
Regulations regarding evaporative emissions have set more and more stringent limits over the last years. To fulfill these specifications, original equipment manufacturers (OEMs) now tend to break down the sum value of evaporative emissions for the whole car onto single parts or components. Especially small, fuel-containing components (fuel lines, pressure sensors, injection systems, etc.) are challenging. Very low emission rates (<1 mg/24 h) must be measured precisely, and also the stability of these values must be verified due to fuel equilibration effects. Standard SHED (sealed housing evaporative determination) systems or test chambers for measuring volatile organic compound (VOC) emissions are often too big and have too high background levels to achieve reliable results. In addition they are quite expensive which affects the costs per measurement. Our aim was to develop a low-cost Micro-SHED system which fulfills the abovementioned requirements. Commercial gas-tight aluminum boxes with a volume of about 73 L were modified using a Tedlar bag and a fan. Four of those boxes can be put in a standard 1 m3 VOC emission test chamber for temperature control. Measurements are performed by one flame ionization detector (FID), which samples the boxes successively. Parameters such as repeatability, recovery, and retention were determined. Results show that the performance regarding these parameters is within the requirement range given by the California Air Resources Board (CARB) Standards and Test Procedures with few exceptions. Background emission rates are less than 0.1 mg/24 h over the CARB Diurnal Soak temperature profile. The parallel measurement of four parts using only one 1 m3 SHED reduces the costs per part considerably. The new Micro-SHED system allows testing more parts in the same time or measuring up to four identical samples in parallel to get more reliable results. This setup was used for the determination of emission rates of fuel hoses, pressure sensors, and injector seals.
The current procedure for testing emissions from new vehicles, the World Harmonised Light Vehicle Test Procedure (WLTP), was introduced in September 2017. The WLTP was developed by collecting over 765,000 kilometres worth of data in order to isolate driver behaviour from other real world variables. However, this is a very time consuming and costly process. This paper discusses the suitability of a cheaper and more time efficient alternative. Driver behaviour has a significant impact on the emissions produced from the same vehicle. This study explores the feasibility of utilising virtual environments as an alternative to real world testing to isolate driver behaviour to develop future drive cycles. The use of virtual environments have some significant advantages over real world testing: they can be strictly controlled in terms of the weather, topography and vehicle characteristics, thereby aiding the isolation of driver behaviour from other variables. A driving simulator facility based at the University of West of England was used to assess the suitability of determining driver behaviour using a virtual environment. A track was created based on a local route in the virtual environment. The virtual route was driven by volunteers and their driving behaviours were identified. The same route in the real world was driven by the same volunteers. The driving behaviour of the volunteers from both the virtual environment and the real world are compared to assess the realism of the virtual driving experience in terms of driver behaviour. Finally the data from the virtual environment were analysed to determine if driver behaviour can be isolated, along with the impact on vehicle emissions, with a view to using virtual environments to develop future drive test cycles for emissions testing.
Catalyzed gasoline particulate filter (cGPF) is the prime technology to meet future stringent regulations for particulates from gasoline direct injection (GDI) engines. One of the technical concerns is the ultimate durability of cGPF in regards to engine lubricant formulations. This study investigated two tailored lubricant formulations on catalyzed GPFs which were aged on engine followed by emission testing on vehicle. An engine accelerated aging protocol was developed for cGPFs to simulate thermal aging, ash and soot loading that is at least equivalent to 200,000 km durability requirement. Evaluations include tailpipe emission levels, backpressure, catalytic performance, and post-mortem analysis. Both formulations have demonstrated a high level of cGPF performance retention; performance being assessed in terms of emission level at the end of durability demonstration testing. These formulations provide flexibility in selecting robust lubricant to meet various system requirements.
A significant share of the emissions of a vehicle with internal combustion engine originates from the cold start. In addition to the more stringent limits for particulate emissions due the introduction of the Euro 6c standard for gasoline engines with direct injection (GDI), exhaust gas emission testing is currently performed applying the real driving emission test procedure (RDE) required by the Euro 6d TEMP standard. The RDE test procedure is not clearly defined, potentially allowing high loads immediately after the engine start. Under such circumstances the combustion chamber features low surface temperatures impairing emission performance and in particular provoking the excessive generation of hydrocarbon and particulate emissions. It is therefore important not only to examine the heating of the catalytic converter during the cold start, but also the preconditioning of the combustion chamber itself. This paper describes the influence of different catalytic converter heating strategies on the emissions during heating operation, as well as during the subsequent load demand. Furthermore, the influence of the engine temperature at engine start is investigated. In addition to a stoichiometric and a lean heating operation strategy another combustion process strategy is presented. The novel strategy provides heating of the combustion chamber, without decreasing the catalyst converter heating significantly. The studies were carried out on a 2.0 liter gasoline engine with direct injection (SIDI) on an engine test bench. Both gaseous emissions and particulate emissions were monitored. Furthermore, the origins of particulate emissions were examined in more detail by means of high-speed camera recordings of the soot radiation inside the combustion chamber. To assess the flame propagation, high-speed camera footage was combined with the signals from a fiber optical sparkplug (FOSP).
The new European Commission Regulations for vehicle certification include a new laboratory procedure for fuel consumption and require Real Driving Emissions (RDE) to be gauged on-road with Portable Emissions Measurement Systems (PEMS). The goal of this investigation is to underline some critical issues in the development of RDE cycles with particular reference to the repeatability on-road and the reproducibility on-track. More specifically, the study includes an optimization of the route for RDE cycles to ensure robustness with respect to traffic conditions, an analysis of emissions variability on-road in hot weather and a discussion about the possibility to reproduce RDE cycles on-track. The tests were performed with a start&stop Diesel Class3b vehicle that was equipped with a PEMS instrumentation and tested over an optimized route in summer in the southern Italy. The tests on the track were performed on the testing facilities of the Nardò Technical Center. The emissions levels measured in the on-road and on-track test were found to be strongly affected by ambient conditions together with engine load and speed and cycle specification in terms of speed and acceleration. This result underlines the necessity of improving the corrections for NOx versus ambient temperature and humidity used in the European Regulation and suggests the possibility to correlate the emissions of NOx and CO2 to some parameters of RDE tests: vehicle speed and acceleration, engine load and speed, ambient temperature and humidity.
To check the regulated emission limits, mass emissions test for a vehicle is conducted on a chassis dynamometer following a driving cycle. However, the driving cycle and laboratory test are different from the real-world driving. This article presents a study conducted on a mid-size gasoline car on chassis dynamometer as well as on-road (real-world). It determines the effect of real-world driving, different drive modes (idle, acceleration, deceleration and cruising) on vehicle emissions and fuel consumption and their comparison with the laboratory data. The emissions tests were conducted on the chassis dynamometer following the Modified Indian Driving Cycle and on the selected traffic routes in Dehradun city using a Portable Emission Measurement System (OBS-2200). It was observed from the study that average on-road emission rates in gram per second were 1.35 to 2.39 times higher for CO, 1.12 to 1.39 times higher for CO2, 2.04 to 2.32 times higher for NOx and 2.17 to 5.0 times higher for THC as compared to the chassis dynamometer test. The test results indicated that the on-road fuel consumption was higher than the dynamometer test by 22.3%, 19%, 13.9% in congested, medium and low traffic routes respectively. The low-speed conditions with frequent stop and go operation, particularly on the congested roads, were the main reasons that aggravated the vehicle emissions and fuel consumption in real-world driving conditions. The time spent in various drive modes and percentage contribution of the drive modes to vehicular emissions and fuel consumption were calculated and analyzed using a computer program developed for the study. This study was also an attempt to generate and understand the real-world vehicle emissions and fuel consumption data in a Tier-II Indian city, and to establish the correlation between the real-world vehicle emissions and emissions data generated in the laboratory as per the legislative procedure.
With the implementation of the “Worldwide harmonized Light duty Test Procedure” (WLTP) and the highly dynamic “Real Driving Emissions” (RDE) tests in Europe, different engineering methodologies from virtual calibration approaches to Engine-in-the-loop (EiL) methods have to be considered to define and calibrate efficient exhaust gas aftertreatment technologies without the availability of prototype vehicles in early project phases. Since different types of testing facilities can be used, the effects of test benches as well as real and virtual vehicle operators have to be determined. Moreover, in order to effectively reduce harmful emissions, the reproducibility of test cycles is essential for an accurate and efficient application of exhaust gas aftertreatment systems and the calibration of internal combustion engines. In this paper, the influence of different human drivers on the particle count of a passenger car with a small turbocharged three-inline-cylinder gasoline engine with intake-manifold fuel injection is presented. Furthermore, the effects of one human driver in comparison to a virtual driver regarding the reproducibility of the test results are shown. In this setup several particulate measurement systems with different measurement principles are taken into account to validate the results. In the second part of the paper, including the same engine and measurement systems, the effects and influences of seasonal RON 95 gasoline fuel qualities (winter and summer) on the size distribution (5,6-560 nm) and the particulate count are discussed. With the introduction of the Euro 6d emission standards, there is no longer a legal specification in place for the fuel to be used for RDE emission testing. Hence, it must be considered that due to seasonal climate changes, specifically designed fuels are sold at regular gas stations. Although summer and winter fuels are supposed to guarantee the same physical properties, they differ in composition which can lead to considerable differences in particulate emissions. To avoid a mixing of the different climate-dependent fuel types during the test program, the fuel tank has been extensively flushed before refilling it with the next test fuel. As prescribed all fuels were bought at public gas stations and have been analyzed by a third-party laboratory to guarantee the immaculateness of each fuel type.
Drive cycles have been an integral part of emission tests and virtual simulations for decades. A drive cycle is a representation of running behavior of a typical vehicle, involving the drive pattern, road characteristics and traffic characteristics. Drive cycles are typically used to assess vehicle performance parameters, perform system sizing and perform accelerated testing on a test bed or a virtual test environment, hence reducing the expenses on road tests. This study is an attempt to design a relatively robust process to generate a real world drive cycle. It is based on a Six Sigma design approach which utilizes data acquired from real world road trials. It explicitly describes the process of generating a drive cycle which closely represents the real world road drive scenario. The study also focuses on validation of the process by simulation and statistical analysis.
Gasoline particulate filter (GPF) is considered a suitable solution to meet the increasingly stringent particle number (PN) regulations for both gasoline direct injection (GDI) and multi-port fuel injection (MPI) engines. Generally, GDI engines emit more particulate matter (PM) and PN. In recent years, GDI engines have gained significant market penetration in the automobile industry owing to better fuel economy and drivability. In this study, an accelerated ash loading method was tested by doping lubricating oil into the fuel for a GDI engine. Emission tests were performed at different ash loads with different driving cycles and GPF combinations. The results showed that the GPF could significantly reduce particle emissions to meet the China 6 regulation. With further ash loading, the filtration efficiency increased above 99% and the effects on fuel consumption and backpressure were found to be limited, even with an ash loading of up to 50 g/l.
There is a distinct difference between plug-in hybrid electric vehicles in the market today. One key distinction that can be made is to classify a plug-in hybrid electric vehicle (PHEV) according to its operational behavior in charge depleting (CD) mode. Some PHEVs are capable of using the electric-only propulsion system to achieve all-electric operation for all driving conditions in CD mode, including full power performance. In contrast, some PHEVs, henceforth termed “blended PHEVs”, cannot satisfy the power requirements of all driving conditions with the electric-only propulsion system and occasionally utilize blended CD operation whereby it is necessary to blend the use of the internal combustion (IC) engine with the use of the electric motor(s) to help power the vehicle. This characteristic can result in a unique phenomenon where it is possible for a blended PHEV to drive for miles in electric-only mode at the start of a trip before encountering a rapid acceleration that generates a need for blended CD operation. Under such circumstances, blended PHEVs can have a high-power cold-start where the initial IC engine start occurs under high vehicle torque demand, even when the battery state of charge (SOC) is high. Conventional IC engine vehicles do not experience high-power cold-starts since the initial IC engine start typically occurs under a very low initial torque requirement when the vehicle is stopped, in park or in neutral, and some driving is usually required before a high-power driving maneuver is encountered. Testing of various blended PHEVs found that high-power cold-starts have different emission characteristics compared to conventional vehicle cold-starts. California Air Resources Board (CARB) staff conducted vehicle tests to investigate the effects of high-power cold-starts on the gaseous exhaust emissions of blended PHEVs. Conditions that triggered high-power cold-starts were characterized from on-road driving and the resulting vehicle speed traces were then used to conduct chassis dynamometer exhaust emission tests. A new methodology was developed to compare the cold-start emissions from the high-power cold-start acceleration cycles to emissions from regulated emission certification test cycles. The results from these tests indicated that high-power cold-starts may be yielding significantly higher exhaust emissions than those observed during the regulated emission test cycles that are conducted for vehicle exhaust emission certification. This paper provides a summary of the high-power cold-start test cycle development, the methodology that was utilized to compare test cycle emissions, and the high-power cold-start gaseous emissions results.
To meet US EPA light-duty vehicle emission standards, the vehicle powertrain has to be optimally controlled in addition to maintaining very high catalyst system efficiency. If vehicles are operated outside the bounds of a standard laboratory exhaust emission test (e.g., on-road or off-cycle) the operating control strategy may shift to optimize other desirable parameters such as fuel economy and drivability. Under these circumstances. The engine control system could be operating in a different state space from an emission control stand point. This control state-space can be observed based on four principal parameters: NOx, Lambda and exhaust temperature (measured at the tailpipe) and vehicle acceleration. These vehicle emission control patterns can be characterized by their corresponding emission control signatures, such as cold start, transient fuel control, and high speed/high load open loop. These emission control signatures are unique to a variety of engine technologies as well. Recognizing these signatures during vehicle operation can identify engine control state space and could estimate NOx mass flow by utilizing an ANN (artificial neural network) for pattern recognition. This could assist in detecting emission testing irregularities that might indicate a malfunctioning emission control system. One advantage to this approach is the equipment overhead to acquire this information is much less compared to other conventional methods such as PEMS (portable emission measurement system). US EPA is investigating this approach, recording the vehicle emission control dynamic signatures during normal dynamometer testing and on-road/off-cycle. Optimized data sets of emission control signatures are currently being used for training an artificial neural network to estimate NOx mass-based calculations and distinguish between well-controlled and uncontrolled systems. This non-intrusive testing method may be used to detect catalyst early failure and monitor emission test irregularities.
The scope of this SAE Information Report is to supply the user with sufficient information so that he may decide whether acoustic emission test methods apply to his particular inspection problem. Detailed technical information can be obtained by referring to Section 2.
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