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Leakage is always a concern in the interface between the cylinder block and the head. Nowadays, sealing of this interface is almost exclusively achieved by multi-layer steel head gaskets. However, it is not only the gasket's quality that is responsible for perfect sealing. An equally important role is played by the surface topography of the mating surfaces. The top surface of the cylinder block and the bottom surface of the cylinder head are machined by face-milling and present periodic tool marks features. Based on the surface topography measured by high definition metrology, this paper presents a novel sealing analysis method to evaluate the sealing performance of the critical topography region around the combustion chambers. The method consists of three modules: tool paths or channels reconstruction, sealing region segmentation based on channels' directions, and sealing analysis on sealing regions with different channel directions. An engineering case demonstrates the sealing analysis procedures and verifies the effectiveness of the sealing analysis method. The analysis of 12 ring-shaped sealing regions found that channels' directions do have a significant impact on surfaces' sealing properties. Circumferential channels or paths are advantageous for surface sealing, while radial channels are prone to leakage.

The cylinder head gasket (CHG) joint is the most critical sealing joint for IC engine performance. Cylinder head bolt preload application should be stoichiometric. Excess cylinder head bolt pre-ten...

The aim of this study is to investigate experimentally gasoline fumigation (GF) and to apply heat release (HRR) analysis for two different compression ratios (CRs) for different gasoline fumigation ratios (GFs) at two engine speeds in an automotive diesel engine. Here, gasoline at 5–20 % (by vol.) ratios was injected in to intake air by using an adapted carburetor. Firstly, GF tests were conducted for original CR (18.25, high compression ratio, HCR) of the engine. Then, CR of the engine was reduced to 17 (low compression ratio, LCR) by changing of cylinder head gasket thickness and GF were also investigated for LCR. In this study, HRR was analyzed by using measured cylinder pressure values. At the end of the experimental study; it was seen that GF creates two peaks in HRR curve for selected all of the operating conditions. The first peak occurs before top dead center (TDC) and the second peak occurs after TDC. The first peak becomes larger and second peak decreases with increasing GFs. This indicates that combustion process is better than that of neat diesel fuel (NDF), especially for low GF ratios. In addition, GF increases cylinder pressure and temperature.

In this study, the effects of gasoline injection into intake air (gasoline fumigation, GF) on the brake specific fuel consumption (bsfc), combustion characteristics such as excess air coefficient and exhaust temperature (Tex), nitrogen oxides (NOx) and opacity were experimentally investigated in an automotive diesel engine. One of the main objectives of this study is to experimentally investigate the effects of GF at the same engine for different compression ratios (CRs). The original CR of the engine is 18.25 (high CR, HCR). Here, CR of the engine was changed to 17 (low CR, LCR) by changing the cylinder head gasket thickness. Thus, experiments were performed for two different CRs such as 18.25 and 17 under five different loads such as 150, 135, 120, 105, and 90 Nm at 2000 rpm and under five different load such as 120, 105, 90, 75, and 60 Nm at 4000 rpm for various gasoline fumigation ratios (GFs). In this study; approximately 5, 10, 15 and 20 %, (by vol.) gasoline was injected into intake air by using an adapted carburetor. The test results showed that GF decreases bsfc for all of the working conditions. NOx emissions decrease with GF for high CR at 2000 rpm, but it generally increases for low CR (17) under high loads. NOx emissions increase significantly with GF for both CRs at 4000 rpm. Opacity decreases at low GFs, but it increases at high GFs. In general, the results of GF at the original CR (HCR) are better than the LCR. However, in the present study, no arrangement has been made in the electronic control unit (ECU) of the engine for changed CR.

Traditional cylinder head gasket design is based on the assumption that the mating surfaces’ form is ideal plane. However, high definition metrology (HDM) shows that the top surface of cylinder blocks and the bottom surface of cylinder heads are far from ideal plane and presents a macro form error. To compensate the macro form error of the mating surfaces, a gasket design optimization method is proposed in this paper. It mainly consists of two modules. The first module is surface alignment and gap calculation. Measured surface topography is aligned by control point registration and the control points are found by region labelling algorithm. The second module is gasket design optimization based on surface gap. A case study shows the details of the proposed gasket design optimization method.

In this paper, the cylinder head gasket of a certain type of diesel engine is taken as the research object. Under the condition of changing the mechanical load parameters, the changing trend of the strength and sealing performance of the cylinder head gasket is analyzed, and then its reliability and durability are evaluated. Through the analysis, we can see that the changing trend of the strength and sealing performance of the cylinder head gasket is the opposite. Therefore, in this paper, the fatigue life and sealing performance of the cylinder head gasket are regarded as factors with equal weight, and the total coordination coefficient is introduced to measure the change of the strength and sealing performance of the cylinder head gasket after changing the explosion pressure and bolt preload, the best loading scheme is selected.

A test to evaluate crevice corrosion in joints of mechanical components sealed with composite structure gaskets in corrosive environments is presented. The crevice corrosion produced in joints comprising the cylinder head, gasket and mono-block was aimed as a study case to illustrate the test. It is based on polarization resistance and potentiodynamic polarization measurements obtaining localized and measurable crevice corrosion on small specimens in a short time. Corrosion rates, crevices volumes and potentiodynamic behavior of assembly specimens made of three different aluminum alloys extracted from actual cylinder heads and mono-blocks, and sections of cylinder head gasket were obtained and reported.

In-cylinder pressure-based heat release analysis is one of the most commonly used tools for engine combustion investigations. Heat release rate calculation based on the first law of thermodynamics relies mainly on two parameters: (1) cylinder pressure and (2) cylinder volume as a function of crankshaft position. The phasing of cylinder pressure and volume (by exact determination of TDC position) is of vital importance because it causes a large error in the calculation of IMEP and heat release. Total cylinder volume determination is directly affected by the value of compression ratio used for calculations. The TDC determination can be pursued by a dedicated TDC sensor (additional hardware) or by thermodynamic methods based on in-cylinder pressure measurement. The different methods for TDC position determination by thermodynamic analysis of measured in-cylinder pressure are presented in this chapter. Compression ratio depends on displacement volume and combustion chamber volume at TDC position. Displacement volume can be calculated within tight limits, but volume at TDC is difficult to determine because it consists of different crevices including the top-land region between piston, first ring and cylinder, head gasket, injectors and valve seats interstices, as well as the spark plug thread. This chapter presents different methods for compression ratio estimation based on in-cylinder pressure traces and evaluates for their accuracy and convergence speed. Blowby and gas flow through the cylinder-piston-ring crevices are phenomena that affect the in-cylinder pressure, the temperature, and the amount of charge during combustion, which affects the performance and exhaust emissions. The models for the estimation of blowby losses are also discussed. Variations in residual gas fraction, wall temperature, and air-fuel mass significantly contribute to cyclic combustion variability in addition to performance and emission characteristics. Thus, estimation of these parameters is necessary for detailed combustion analysis. This chapter presents the methods for determination of residual gas fraction, cylinder wall temperature, and air-fuel mass using in-cylinder pressure measurement.

Establishing the homogeneous charge compression ignition (HCCI) process in a diesel engine, in order to improve exhaust emission quality while extending the HCCI regime, is one of the challenges in applying HCCI in worldwide applications. This can be done by decreasing the compression ratio, and controlling the exhaust gas recirculation (EGR) rate and charging temperature. In this paper, an original single cylinder diesel engine was converted to n-heptane-fueled HCCI with the fuel injected into the intake manifold. At the designed compression ratio of 20:1, the HCCI engine could operate stably at low speed (from 1600 rpm to 2000 rpm) and low load (10% to 20% load). In addition, reducing the compression ratio from 20:1 to 14.87:1 by changing the thickness of the cylinder head gasket and with no EGR applied extended the operating range to 50% load and 3200 rpm speed.

The present work addresses crevice and galvanic corrosion processes occurring at the cylinder head gasket/cylinder head interface and cylinder head gasket/cylinder liner interface of four-stroke medium-speed diesel engines for marine applications. The contact between these systems and the marine environment can promote formation of demanding corrosion conditions, therefore influencing the lifetime of the engine components. The electrochemical behavior of various metals and alloys used as head gasket materials (both ferrous alloys and copper alloys) was investigated. The efficacy of corrosion inhibitors was determined by comparing electrochemical behavior with and without inhibitors. In particular, crevice corrosion has been investigated by electrochemical tests using an experimental set-up developed starting from the requirements of the ASTM G-192-08, with adaptation of the test to the conditions peculiar to this application. In addition to the crevice corrosion resistance, the possible problems of galvanic coupling, as well as corrosive reactivity, were evaluated using electrochemical tests, such as potentiodynamic measurements. It was possible to quantify, in several cases, the corrosion resistance of the various coupled materials, and in particular the resistance to crevice corrosion, providing a basis for the selection of materials for this specific application.

In order to accurately estimate the temperature reached in the cylinder block and cylinder head gasket of an internal combustion engine, an experimental investigation of the thermal contact resistance (TCR) across cylinder head gasket is performed. TCR has been calculated for contact pressure up to 42 MPa which corresponds to the clamping pressure of the gasket. Different sections (inter-cylinders, oil, and water ribs) with different law behavior have been retained. The temperature evolution has been recorded using thermocouples immerged in the measurement device. The heat flux has been calculated using this temperature evolution. The TCR has been deduced using Fourier law. Results show that the TCR decreases with increasing the load and tends toward a constant value for various sections of the gasket. In addition, TCR values are more important for the inter-cylinder’s section which will result in greater values of temperature near inter-cylinder’s section on the cylinder block.

Today, environmental concerns push for new technologies to reduce our energy dependence on fossil fuels. The use of treated biogas in dual-fuel diesel engines is common as it has no major effects on engine performance and it only requires minor engine modifications, consisting mostly on premixing and injection timing advance. However, biogas itself cannot be directly used in engines because of degradation caused by acid attacks and sulfidation, making sulfur compound filtration a necessity. In this case, biogas use is economically competitive for relatively big installations with electrical power above ≈100–200 kW. Simple, low-costs solutions are needed for small installations (below 100 kW). The objective of this paper is to assess the degradation of a 3.1 kW diesel engine in dual-fuel mode with preheated untreated biogas with phase separation. The modifications on the engine consist only in an exhaust/biogas heat exchanger with phase separation and lubricant replacement with a higher total base number. These changes are relatively costless compared to removing sulfur from the biogas. A test engine did function for 550 h with preheated untreated biogas containing 2000 ppmv of H2S. The load was maintained at 60% of maximum load with 50% of diesel replacement with biogas. Degradation was monitored by visual inspection, weight and size measurements of engine parts, in-cylinder pressure measurements, and oil analysis. Dismantling of the engine at the end of the experiment showed almost negligible signs of degradation. For comparison purposes, a similar test was conducted on the engine with the same operating conditions but without biogas preheating or phase separation. The degradation observed was noticeably more important in that experiment as the oil total base number decreased faster and cylinder head gasket wear was more important. Biogas preheating with phase separation seems a promising low-cost alternative for biogas use in small farms as it limits acid attacks and sulfidation in engines.

As the important part of the internal-combustion engine, cylinder head bears high thermal loads and mechanical loads. In order to analyse the merits or defects of cylinder head cooling system , built the 3-D model of cylinder head, and analysed the heat transfer processes between cylinder head and cooling water by fluid-solid coupled simulation in STAR-CCM+. The pressure nephograms and velocity vector of cooling water in the water jacket, and the whole temperature distributions of cylinder head were acquired. And analysed separately the temperature fields of fire power faces and exhaust passages which were under high heat loads .According to the analysis results , the structrue of cylinder head water jacket was evaluated and corresponding suggestions was put forward.

This paper describes the design and performance of a miniature cylinder pressure sensor packaged either as a stand-alone device or integrated with a cylinder head gasket, glow plug, fuel injector, or spark plug. Benefitting from a fiber-optic based design the sensing element can operate at ultra-high temperatures and is not affected by EMI. This low cost device utilizes the principle of light intensity changes transmitted by two optical fibers upon reflection from a metal diaphragm deflecting under the effect of pressure. When the diaphragm thickness and shape are optimized, the sensor can operate up to 5 billion pressure cycles. The device is compensated for all temperature effects encountered in combustion engines, resulting from the thermal shock, engine load changes, and under-hood temperature fluctuations. Due to the diaphragm small thermal mass the sensor is subject to the thermal shock error if no heat shield is employed. While a suitable shield can almost eliminate the thermal shock error, it can get clogged in engines fuelled by diesel or landfill gas. For such engines a dual diaphragm construction offers a robust solution against soot and other combustion deposits as well as minimum thermal shock error. In comparison to a water cooled piezoelectric quartz transducer the present sensor offers the accuracy of ±1.5% of reading at pressures above 5 bars, ±0.1 bar error at pressure below 5 bars during compression, and the thermal shock error ranging from 0.1 bar to 0.3 bar dependent if a single or dual diaphragm is used. Such accuracy is possible with both stand-alone sensors as well as those 1.7 mm in diameter used in the “pressure sensing” cylinder head gaskets, glow plugs, fuel injectors, or spark plugs. This accuracy is maintained under all combustion conditions, sensor tip continuous temperatures up to 380 oC, signal conditioner temperature range of –40 oC to 140 oC, pressures up to 350 bar, and over frequency range of 0.1 Hz to 30 kHz. Such remarkable accuracy allows advanced engine controls based on highly accurate values of the Indicated Mean Effective Pressure, Mass Fraction Burned, Maximum Pressure Gradient, and Peak Pressure. Benefitting from sensor’s high accuracy at both low and high pressures the device enables closed-loop control of fuel injection as well as in-cylinder prediction of mass air flow and engine NOx emission levels.

This paper focuses on discussing the application of FEA theory and method in calculation of composite structure strength between engine cylinder head and head gasket. Based on finite element analysis software, the integrated system of 3D CAD/CAE application software was developed for the finite-element analysis of the composite structure consisting of engine cylinder head and head gasket. By using the software system, several jobs, such as working condition analysis from preloading to outburst operation, structural analysis and steady-state thermal analysis, and thermo-structure coupling analysis, were carried out. The results studied in this paper provide a new idea and method for the finite element analysis of composite structure between engine cylinder head and head gasket.

The spatial fuel vapor distribution of the homogeneous charge by a 6-hole injector was examined in a optically accessed single cylinder direct injection spark ignition(DISI) engine. The effects of in-cylinder charge motion, and fuel injection pressure, and coolant temperature were investigated using a planar LIF (Laser Induced Fluorescence) technique. It was confirmed that the in-cylinder tumble flow played a little more effective role in the spatial fuel vapor distribution than the swirl flow during the compression stroke at 10 mm and 2 mm planes under cylinder head gasket and the increased fuel injection pressure activated spatial distributions of the fuel vapor. In additions, richer mixtures were concentrated around the cylinder wall by the increase of the coolant temperature.

The Cylinder head gasket (CHG) joint is the most important sealing joint for IC engine performance. Cylinder head bolt preload application should be stoichiometric. Excess cylinder head bolt pre-tension develops more stresses and extra bore deformation and insufficient cylinder head bolt pre-tension leads to gasket leakage. Uniform pressure distribution is required on cylinder head gasket but it is not possible because of varying stiffness of the head and block. Hence maximum pressure distribution is better for avoiding the leakages. Bore deformation, engine blow-by and lubricating oil consumption (LOC) of the engine minimum is better for achieving stringent emission norms. Influences of application method of preload, cylinder head bolt tightening pattern and number of passes are investigated on gasket pressure distribution, bore deformation, engine blow-by and LOC. FEA non-linear analysis is carried out for gasket pressure distribution and bore deformation. Piston and piston ring software is used for simulating engine blow-by and LOC. For optimizing controllable parameters Taguchi design of experiments method is used for robust and optimized design. Study reveals that tightening parameters influences are significant. This study is very important for IC engine efficiency improvement and engine CO2 emission reduction at design stage for new engine development program.

Machine configuration selection has a great impact on the system-level reliability of a manufacturing system, while the absence of proper consideration of the product quality and the tool degradation on tool failure when determining the machine-level reliability is likely to result in unanticipated machine downtimes or inappropriate maintenance decisions. A generic methodology is thus developed to incorporate both the machine-level and the system-level reliability analyses. Firstly, the machine-level reliability is investigated based on the product dimensional quality and the tool degradation. A novel machine-level quality reliability-integrated model is developed to address the interaction between product quality and tool reliability. The developed machine-level reliability model is then used to estimate the system-level reliability for a manufacturing system with selected configurations. Various hybrid configurations of the multi-operational manufacturing system are investigated in terms of the system-level reliability. The analytical procedure and the effectiveness of the proposed methodology are demonstrated through an example of a serial-parallel hybrid system for cylinder head gasket machining.

Your classic Jaguar XK 120 stands useless by the roadside. Why? Because you gave priority to the admittedly gorgeous 6 cylinder straight six engine; because you privileged the highest value part. Rubber pipes perish, though, and now thanks to a leak in a cheap hose the head gasket has blown. You are stranded and facing a costly bill. More seriously, your mechanical gaffe is a sign of your misunderstanding of Deleuze. Like Sir William Lyons, he engineers systems where the concept of priority must not be confused with independence, separateness, abstraction or ethical superiority. As a good engineer, Deleuze's constructions are holistic and opposed to abstract hierarchies: if a crucial small, actual part perishes in a particular practical situation where it has a role to play, then it does not matter how much virtual power you have in reserve. Your feet are still in a pool of hot water as you survey the wasted potential of actual motion and ideal expressions, hand made in Coventry.

Engine gasket is the thin steel plate with coatings. Its compressive deformation affects the height of engine assembly, which changes combustion chamber’s volume and then influences engine performance. In this paper, the assembly simulation of head, block and gasket was studied. Then a further simulation takes the thin coatings on steel sheet into consideration. In the second simulation, gasket’s partial micro-model in micron-scale meshes was established and deformation of coatings was analysed. The combination of deformations explores the cause of fluctuations of gasket’s tightened thickness and obtains more precise numerical results of tightened thickness at different positions. Moreover, a lead pellet test was carried out to verify the results of tightened thickness calculation.

The new concept spark plug was developed to study its influence on the combustion characteristics of SI engine. It has pre-ignition chamber in the lower end of spark plug and flame hole, in which fresh mixture gas can be introduced without any fuel supply system. This spark plug was tested with a commercial SI engine. Fuel consumption rate, emission gas and MBT timing were measured in the engine dynamometer for various flame hole numbers, hole positions, hole sizes of the pre-ignition chamber of the spark plug. And average flame propagation speed was measured by using the head gasket ionization probe in single cylinder engine. The new concept spark plug induces fast bum in combustion compared with the conventional spark plug, and MBT(Minimum advance for Best Torque) timing was retarded about crank angle. The flame hole number, hole direction and volume of pre-ignition chamber were found to influence the combustion characteristics.

This paper presents a heat transfer analysis of a head gasket for an internal combustion (IC) engine. A steady state temperature analysis was conducted to investigate the effect of engine material on gasket temperature. Transient temperature analysis was also conducted to investigate temperature variations of gasket materials and the required time to reach steady state temperature. The transfer of heat from the combustion chamber into the wall (a positive heat flux) which occurs after the ignition and the reverse of this process during the expansion stroke (a negative heat flux) were mathematically represented using the Fourier series.

The maximum combustion pressure (Pmax) tends to increase in a diesel engine. This leads to the cylinder head gasket sealing being exposed to tough conditions which can result in gas leakage. In this study, the main factors affected by the rise in Pmax are analyzed and also from perspective of treatment orientations not only for cylinder head gasket but also total sealing engine are proposed.

To avoid the escaping gas from the engine affecting the overall performance of the engine during operation, both the proper pre-stressing force of the bolts as well as the gasket design are critical factors in enhancing the efficiency of the sealing of the gasket. In this investigation, both the distribution of the contact pressure on the gasket, and the stresses of the cylinder head at different loading conditions, such as cold assembly, hot assembly, cold start, and hot firing, are explored by numerical calculation based on the finite element method (FEM). The results reveal that the efficiency of the sealing of the head gasket depends on the pre-stressing force of the hold-down bolts, without taking into consideration any thermal stresses resulting from the temperature distribution in the cylinder head. However, the location of maximum contact pressure on the gasket is transformed when the thermal loading is taken into account. In addition, this research also conducts the parametric analyses for the pre-stressing force of the bolts and compares the differences between cold assembly and cold start conditions.

The primary task of conventional cylinder head gaskets is to provide a reliable seal. The new SensoriCS® head gaskets from Victor Reinz with integrated temperature sensors use the excellent locations in the immediate vicinity of the combustion chambers for temperature measurement, whereby the measurement signals from inside the engine are taken directly to the outside. Highly dynamic signals allow an optimum adaptation of the cooling media flow to the prevailing engine conditions. This leads to higher engine efficiency, reduced fuel consumption, and lower exhaust emissions during the warm-up phase as well as normal operation. Another important advantage lies in the fact that the sensors are installed in the engine during the normal process of mounting the head gasket.

Experiments on a small, one-cylinder high-speed diesel engine were performed by changing the temperature of cooling water and also by changing the material and configuration of the cylinder head gaskets. Three kinds of cylinder head gaskets were made. The temperature was abruptly changed and the temperatures at several points of the cylinder head gasket and its peripheral region, the relative displacement between cylinder head and cylinder block, the loads of the cylinder head bolts, the indicator diagram, the pressure of gasket surface and combustion gas leakage were measured. The sealing characteristics in the transient state and the steady state of the cooling water temperature were investigated from an experimental standpoint. The effect of the temperature differences between the cylinder head, cylinder block and head bolts on the loads of the head bolts and the relative displacement between the cylinder head and cylinder block were observed for the test gaskets.

With the conventional evaluation method of the curing speed (using tack-free time) of a fluid sealant (referred to as a gasket), evaluation of the cured state of the surface of the discrete gasket is possible. In contrast, a method using heat analytical equipment enables an evaluation of the cured state to be conducted in an assembled condition. This evaluation method was used to study gasket specification and the flange shape necessary for joining an aluminum flange with the steel plate of an engine oil pan.

This article presents a critical review of the studies performed to investigate combustion-chamber crevices as sources of hydrocarbon (HC) emissions, and an evaluation of potential technologies for reducing these emissions. Of the combustion-chamber crevices, the piston upper crevice volume is the main contributor to engine-out HC emissions. Chamfering the piston crown or reducing the top-land height and/or the volume behind the top compression ring may result in significant reductions in HC emissions. Modest reductions may also be achieved by reducing the central-electrode crevice of the spark-plug. However, reducing the head gasket crevice of current production engines appears to have little effect on engine-out HC emissions. In general, the sensitivity of the HC emissions to the combustion-chamber crevices is influenced strongly by the in-cylinder flow field and combustion, which influence the concentration of burned gases in the crevice gases.

The aim of the research work presented here is to control the geometric distortions of engine cylinders, which involve both noise and oil consumption. The final goal is then to limit pollution from engines. The simulation deals initially with the cold stamping and crushing operations of a cylinder head gasket; based on using solid finite element models from the Abaqus computer code (version 5.3) for large deformation with plasticity and contact, including friction. In addition, experiments have been carried out to identify the plasticity rule for the materials used in order to simulate the crushing of the cylinder head gasket under a given normal pressure representing the clamping operation. The main difficulty of this work is to correlate the cylinder head gasket behaviour and cylinder distortions with the main function of the gasket, i.e. pressurized gas sealing. The cylinder head gasket is a complex multilayered structure made of three spot welded metal sheets. This assembly has many holes of different shapes. Around the cylinder hole on both outer layers of the gasket, there is a small size embossment to ensure gas sealing between the engine block and cylinder head. This rib is not circular because of the combustion chamber shape.

A two-dimensional (axisymmetric) transient heat conduction in components computer program (HCC) was successfully developed for predicting engine combustion chamber wall temperatures. The alternating direction explicit (ADE) Saul'yev method, an explicit, unconditionally stable finite difference method, was used in the code. Special treatments for the head gasket and the piston-liner air gap, the piston movement, and a grid transformation for describing the realistic piston bowl shape were designed and utilized. The results were compared with a finite element method and were verified to be accurate for simplified test problems. In addition, the method was applied to realistic problems of heat transfer in an Isuzu engine and a Caterpillar diesel engine, and gave good agreement with available experimental measurements.

Currently applied diagnostic systems of technical condition use more and more advanced methods of gathering and processing input data. Many scientific research centres all over the world deal with problems connected with this topic. Up till now no such unified set of guidelines has been constructed which would allow for construction of properly functioning diagnostic system no matter which object is chosen. That is why there is a constant need to test the possibilities of application of existing methods and their modification to match given diagnostic cases. In this article the results of tests conducted with the use of Bayes classifier for diagnostic purposes are presented. The purpose of the tests was diagnosis of technical condition of head gasket in internal combustion engine of a car. The source of information about technical condition was the vibration signal measured in various measurement points. In order to describe the character of changes occurring in vibration signal the measurement in form of entropy was marked for decomposed signal with the use of discrete wavelet transform (DWT).

This paper reviews a countermeasure development of leakage from coolant seals of head-gaskets in a diesel engine applying the Decomposition Analysis and Resolution Process (DAR). We can find complexity arising from some causes of leakage even in a simple square-ring rubber seal. The major causes are (1) large displacement around a head-gasket generated by the combustion, (2) seal distortion at a high compression, (3) seal rubber degradation induced by coolant microorganism deterioration, (4) uncontrolled seal production and (5) unsuitable rubber composition. Through our DAR, we can resolve the complexity of the leakage and can clarify all the cause positions and their relationships. We can confirm that an improved silicone rubber seal, which has a higher fatigue strength, an excellent acid-resistance and a uniform contact property, is the correct resolution. This paper also shows development of a hydrogenated nitrile rubber seal as a permanent measure, which can extend the Middle of Life (MOL) of Product Lifecycle Management (PLM) of the industrial diesel engine production.