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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Automotive Engineers
Journal Basic Information
Journal DOI :
The Korean Society of Automotive Engineers
Editor in Chief :
Volume & Issues
Volume 15, Issue 6 - Nov 2007
Volume 15, Issue 5 - Sep 2007
Volume 15, Issue 4 - Jul 2007
Volume 15, Issue 3 - May 2007
Volume 15, Issue 2 - Mar 2007
Volume 15, Issue 1 - Jan 2007
Selecting the target year
Assessing Traffic Safety Benefits of Technical Regulation for Pedestrian Leg
Oh, Cheol ; Kim, Beom-Il ; Kang, Youn-Soo ; Shin, Monn-Kyun ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 1~9
This study proposes a methodology to assess the traffic safety benefits of technical regulation for pedestrian leg. Traffic safety benefit is defined as the injury reduction in this study. Actual accident analysis and simulation experiments using LS-Dyna3d are conducted to establish statistical models for developing the methodology. The relationship between collision speed and parameters of the regulation is explored. An application example of the proposed methodology is also presented for more comprehensive understanding. It is believed that the proposed methodology would be greatly utilized in developing various technologies and policies to protect pedestrian.
Study on Geometry Design of Lip-Seal for Automobile Wheel Bearing Considering Drag Torque and Sealing Performance
Huh, Young-Min ; Lee, Kwang-O ; Sim, Tae-Yang ; Kang, Sung-Soo ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 10~16
A rubber seal for wheel bearing which has been mainly applied to car wheel supporting device is required to have both high sealing performance and drag torque. Because of severe operational conditions like infiltration of mud or splashed water, the importance of rubber seal which is aimed for leakage prevention of grease and effective blocking of foreign substances has been increasing continuously. The sealing performance of this seal depends on several factors such as materials of seal, friction conditions of contact regions and geometry of seals and so on. We have focused on the effects of geometric characteristics such as the angle of main lip, interference between lip edge and inner metallic ring. In this study, the optimization of geometric variables was performed using the finite element analysis. For the sake of finite element analysis, uniaxial tensile tests were conducted and several constants for Mooney-Rivlin's equation were obtained. According to the results of this study, mock-up bearing was made. To verify this study, drag torque and mud spray test were preformed.
Weight-reduction Prediction for the Conceptual Design of Carbody with Shell Type Sections Using the Material Substitution Technique
Koo, Jeong-Seo ; Cho, Hyun-Jik ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 17~26
In this paper, a theoretical approach is studied to predict structural performances and weight reduction rates of a car-body with shell type sections in case that its materials have to be substituted. For the material substitution design of a car-body, bending, axial and twisting deformations are considered under constant stiffness and strength conditions, which utilize some new indices derived from a structural performance point of view. The developed indices to measure the weight reduction by the material substitution give good guidelines on conceptual design of car-bodies.
A Study of Head-Up Display System for Automotive Application
Yang, In-Beom ; Lee, Hyuck-Kee ; Kim, Beong-Woo ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 27~32
Head-Up Display system makes it possible for the driver to be informed of important vehicle data such as vehicle speed, engine RPM or navigation data without taking the driver's eyes off the road. Long focal length optics, LCD with bright illumination, image generator and vehicle interface controllers are key parts of head-up display system. All these parts have been designed, developed and applied to the test vehicle. Virtual images are located about 2m ahead of the driver's eye by projecting it onto the windshield just below the driver's line of sight. Developed head-up display system shows satisfactory results for future commercialization.
Crush FE Analysis of Front Side Assembly of Passenger Cars for Identifying the Roles of Major Parts Influencing on Collapse Mode with Reverse Engineering
Kim, Yong-Woo ; Kim, Jeong-Ho ; Jeong, Kyung-Shin ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 33~40
Crashworthiness design is of special interest in automotive industry and in the transportation safety field to ensure the vehicle structural integrity and more importantly the occupant safety in the event of the crash. Front side assembly is one of the most important energy absorbing components in relating to the crashworthiness design of vehicle. The structure and shape of the front side assemblies are different depending on auto-makers and size of vehicles. Thus, it is not easy to grab an insight on designer's intention when you glance at a new front side member without experiences. In this paper, we have performed the explicit nonlinear dynamic finite element analysis on the front side assembly of passenger cars to identify the mechanical roles of major parts in relation to collapse modes from the viewpoint of reverse engineering. To do this, we have performed crash FE analysis for the two different assemblies of small car and heavy passenger car and have compared dynamic behaviors of the two.
Development of Shift-By-Wire System for an Automatic Transmission Equipped Vehicle
Kim, Jung-Yun ; Yim, Chung-Hyuk ; Lim, Won-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 41~46
This article deals with the design and prototyping of Shift-By-Wire system for an automatic transmission equipped vehicle. In order to manipulate the shifting action electronically, Shift-By-Wire system consists of an electronic shift lever, an electric shift actuator and position sensors. The shift lever is designed to transform the driver's shifting command into an electric signal; it includes the position sensor using non-contact type hall sensor and an additional shifting switch acting as Tip-tronic. For the design of an electric shifting actuator, we investigated the stroke angles and shifting efforts of the manual control lever in each shifting section. And the position sensor of the shifting actuator is designed by using a potentiometer with an optical encoder. Finally the prototype of Shift-By-Wire system was built in a conventional 2.4L class SUV vehicle, and we performed road tests in order to verify its performance.
Optimum Design of Formed Tool for Die of Bearing Rubber Seal Using Design of Experiments
Lee, Li-Hai ; Lim, Pyo ; Lee, Hi-Koan ; Yang, Gyun-Eui ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 47~53
A bearing is one of core parts in automobile. Rubber seal of the bearing is important to improve performance of bearing, formed by hot-press die of rubber seal for the intricate shape. In this study, formed tools are used to machine die of bearing rubber seal and the machining operation is classified into the several process of high precision. Design of experiments is used to optimize selection of the formed tools for the efficient machining of the hot-press die. The cutting force, tool wear and tool life are determined to characteristics. And, the clearance angle, the rake angle and the length cutting edge are considered as the major factors. Experiments are repeated to use one-way factorial design, and tool life is predicted by regression model.
Spray Behavior Characteristics of Injector Used for HC-DeNOx Catalyst System in the Transparent Exhaust Manifold
Lee, Dong-Hoon ; Oh, Jung-Mo ; Jeong, Hae-Young ; Lee, Ki-Hyung ; Yeo, Kwon-Gu ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 54~60
A new method that optimizes a control of hydrocarbon (HC) addition to diesel exhaust gas for HC type DeNOx catalyst system has been developed. These catalysts are called as the HC-DeNOx catalyst in this paper. The system using HC-DeNOx catalyst requires a resonable quantity of hydrocarbons addition in the inlet gas of the catalyst, because the HC concentration in a diesel engine is so low that the HC is not sufficient for NOx conversion. Generally ambient temperature in the exhaust manifold is
, so spray behavior in this case is different from that of any other condions. This research shows spray behavior of injected hydrocarbons in the transparent exhaust manifold.
A Study on Characteristics for Emission Characteristics and Durability with Biodiesel Fuel(20%) in a Commercial Common Rail Type Diesel Engine
Choi, Seung-Hun ; Oh, Young-Taig ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 61~66
A CRDI diesel engine used to commercial vehicle was fueled with 20% biodiesel fuel(BDF 20) in excess of 150 hours. Engine dynamometer testing was completed at regularly scheduled intervals to monitor the engine performance and exhaust emissions. The engine performance and exhaust emissions were sampled at 1 hour interval for analysis, Also, BSEC with BDF 20 resulted in lower than with diesel fuel. Since the biodiesel fuel used in this study includes oxygen of about 11%, it could influence the combustion process strongly. So, BDF 20 resulted in lower emissions of carbon monoxide, carbon dioxide, and smoke emissions without special increase of oxides of nitrogen than diesel fuel. It was concluded that there was no unusual deterioration of the engine, or any unusual change in exhaust emissions from using the BDF 20.
Effects of Operating Parameters on Cooling Performance of a Transcritical
Mobile Air-Conditioning System
Lee, Jun-Kyoung ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 67~75
This paper deals with the research for the effects of the operating parameters that could be used for a transcritical
mobile air-conditioning system on the cooling performance. The experimental conditions of the performance tests for a system and components such as a gas cooler and an evaporator were suggested to compare the performance of each with the standardized test conditions. And this research presents experimental results for the performance characteristics of a
mobile air conditioning system with various operating conditions such as different gas cooler inlet pressures and frontal air velocities/temperatures passing through an evaporator and a gas cooler. Experimental results show that the cooling capacity was more than 5kW and coefficient of performance (COP) was more than 2.1, also. Therefore, we checked that the mobile air-conditioning system using
has good performance compared to that using HFC-134a.
The Effect of Multiple Injections on the Stability of Combustion and Emissions Characteristic in a Passenger Car Diesel Engine
Roh, Hyun-Gu ; Lee, Chang-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 76~82
This paper described the effect of the multiple injections on the stability of combustion and emission characteristics in a direct injection diesel engine at various operating conditions. In order to investigate the influence of multiple injections in a diesel engine, the fuel injection timing was varied one main injection and two pilot injections at various conditions. The experimental apparatus consisted of DI diesel engine with four cylinders, EC dynamometer, multi-stage injection control system, and exhaust emissions analyzer. The combustion and emission characteristics were analyzed for the main, pilot-main injection, pilot-pilot-main injection strategies. It is revealed that the combustion pressure was smoothly near the top dead center and the coefficient of variations is reduced due to the effect of pilot injection. Also,
emissions are dramatically decreased with pilot injection because the decrease of rate of heat release. However, the soot is increased at early pilot injection and main injection.
Development of 3-axis Loadcell for Measuring the Side Force of MPV Using Design of Experiment
Chu, Sung-Il ; Park, Jun-Hyub ; Lee, Jin-Gun ; Park, Ji-Young ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 83~93
This paper represents the development of 3-axises loadcell for measuring the side-force of suspension module of MPV(Multi Purposed Vehicle). The side force causes the failure of damper, such as leakage. The loadcell was developed using strain gauges, and the Wheastone bridge circuit to compensate for the cross-talk between the each axises and the measurement error by temperature. Structure analysis of loadcell was accomplished with FEM(Finite Element Method) to optimize the location of strain gages. The design optimization for important factors that have an effect on performance of loadcell was accomplished by using DOE(Design of Experiment). Loadcell was produced and successfully tested, showing good sensitivity and low cross-talk. The cross-talk of the developed loadcell is bellow 5%. The load history was measured at proving ground. The maximum side-force, the longitudinal force, and vertical force of MPV are 4.2 kN, 8.0 kN, and 17.0 kN, respectively, at Belgian road.
Effects of Nozzle Length-diameter Ratio on Internal and External Flow Characteristics of Biodiesel Fuel
Park, Su-Han ; Suh, Hyun-Kyu ; Lee, Chang-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 94~100
The purpose of this work is to investigate the effect of properties of diesel and biodiesel fuels on the nozzle cavitation and the effect of the length/diameter(L/D) ratio on internal and external flow pattern of nozzle at the various injection conditions. In order to study the effect of the L/D ratio on the nozzle cavitation characteristics of diesel and biodiesel, the characteristics of cavitation flow in the nozzle are visualized and analyzed at the injection pressure of 0.1 MPa to 0.7 MPa by using the visualized images. It was founded that the cavitation was formed in the nozzle orifice at the low injection pressure and the breakup of the issuing liquid jet was promoted at the low L/D ratio. When the L/D ratio decrease, cavitation beginning and growth were affect by cavitation number and Reynolds number.
A Wear of Engine Valve and Seat Insert Seating Face Depending on Cycle Numbers
Kim, Jae-Hak ; Chun, Keyoung-Jin ; Hong, Jae-Soo ; Youn, Young-Han ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 101~107
This study investigated the wear of the valve and seat insert seating faces. A tester, an exhaust valve and a seat insert were used. Test variables were cycle numbers (
) and Hz (10Hz and 25Hz). The other test conditions such as temperature (
), fuel (LPG) and load (1960N) were fixed. The 10Hz tests indicated that the average Rmax of the valve increased at the rate of
cycles starting from
cycles and that of the seat insert increased at the rate of
cycles starting from
cycles. The 25Hz tests indicated that the average Rmax of the valve increased at the rate of
cycles starting from
cycles and that of the seat insert increased at the rate of
cycles starting from
cycles. The tribochemical reaction product covered the two seating faces, preventing the wear of the seating faces. As cycle numbers became greater, the average Rmax of the seating faces became greater, but the increase rate varied significantly depending on the Hz. The wear mechanism of the two faces was investigated through the tribochemical reaction.
Effects of Flow Uniformity on Exhaust Pulsation Pressure in Catalytic Converter for Motorcycle
Yi, Chung-Seub ; Chung, Han-Shik ; Jeong, Hyo-Min ; Lee, Cheol-Jae ; Bae, Tae-Yeol ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 108~114
This research represents the catalytic converter for application in the motorcycle. We have to consider about catalytic converter for reducing exhaust gas strength regarding the displacement volume enlargement. The catalytic converter has been widely used to satisfy the regulations of pollutant emissions from automobiles. Recently, all catalytic converter researches are about automobile. Study about motorcycle catalytic converter has not been conducted yet. In this study, flow uniformity and pressure distribution were simulated in the monolithic inlet of catalytic converter for motorcycle. Exhaust pulsation pressure was set as transient condition about. It was found that flow uniformity shown in base model (0.85) was lower than megaphone model (0.98).
Validation of Contact Modeling Technique for Dynamic Analysis of Roller Bearing System
Jung, Eun-Kyo ; Choi, Jin-Hwan ; Rhim, Sung-Soo ; Ryu, Han-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 115~123
In this paper, an analytical model is developed to describe the dynamic characteristics of a roller bearing. In order to obtain accurate dynamic response of roller bearing, each roller is modeled as a rigid body, which has radial and axial movement and rotational constraints. Beam element between outer race segments is used to consider flexibility of outer race. Beam deflection is calculated from beam forces and used for contact between roller and outer race. The efficient contact search kinematics and algorithms in the context of the compliance contact model are implemented to detect the interactions between roller and race for the sake of speedy and robust solutions. The numerical results are validated with another analysis results which are calculated using waviness condition. Increasing rollers, dynamic responses are compared with each other. In order to confirm dynamic behavior and nonlinear characteristic of roller bearing, Poincare map is used.
Experimental and Numerical Study on Behavior of Impinging Spray according to Ambient Temperature
Shim, Young-Sam ; Choi, Gyung-Min ; Kim, Duck-Jool ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 124~131
The numerical study on behavior of impinging spray from high-pressure swirl injector under various ambient temperatures was performed by using spray vaporization model and spray-wall impingement model implemented in modified KIVA code, and these spray models were estimated by comparison with experimental results. To compute the spray-wall impingement process, the Gosman model, which is based on the droplet behavior after impingement determined by experimental correlations, was used. The modified Abramzon and Sirignano model, that includes the effects of variable thermodynamic properties and non-unitary Lewis number in the gas film, was adapted for spray vaporization process. The exciplex fluorescence measurements were also conducted for comparison. The experimental and numerical analysis were carried out at the ambient pressures of 0.1 MPa and at the ambient temperature of 293 K and 473 K, and the spray characteristics, such as spray-wall impingement process, gas velocity field, SMD and vapor concentration, were acquired. It was found that the impinging spray develops active and SMD is small at vaporization conditions.
Study on the Pressure Variation in a Chamber Caused by Pulsation Pressure
Yi, Chung-Seub ; Shim, Kyu-Jin ; Akbar, Wanda Ali ; Chung, Han-Shik ; Jeong, Hyo-Min ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 132~138
Experimental results of pulsating pressure behavior inside a chamber have been confirmed by computational work. Inside-cylinder pressure shows unstable condition at low rpm. This is caused by plate-type suction valve. It has effect up to inlet of the chamber. But trembling phenomenon is reduced as the pressure is enlarged by increasing the rpm. Result comparison between experimental and numerical analysis shows pulsation reduction is affected by the chamber. We can confirm that compressible effect of the working flow is shown at chamber inlet by increasing rpm. On the other side, this effect is declined at chamber outlet by increasing rpm. It means outlet pressure is going on balance with atmosphere pressure. Buffer plate-type chamber has efficiency of pulsation flow reduction.
Study for the Actuation of Lifter by the Bi-Directional Pump and Single-Rod Cylinder
Lee, Seong-Rae ; Kim, Je-Min ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 139~145
The motion of single-rod cylinder is typically controlled by the directional control valve. In some case, the hydraulic system should be energized by the man power and at the same time the motion of a cylinder is controlled manually. It may be confusing for a man to do two things at the same time. The solution is to make up the closed hydraulic circuit with the bi-directional pump and single-rod cylinder without using a directional control valve. In the case of single-rod cylinder, the flows at the rod side and head side are so different that several valves should be installed to make the motion of single-rod cylinder possible. The hydraulic system is composed of a bi-directional pump, a single-rod cylinder, pilot operated check valves, a check valve and a counter balance valve for the purpose of actuating the lifter. The characteristics of a suggested system are analysized mathematically and numerically.
A Study of NO Fmission Characteristics in a Non-premixed Counterflow Flame with
Lee, Kee-Man ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 146~153
The detailed chemistry with reaction mechanism of GRI 2.11, which consists of 49 species and 279 elementary reactions, have been numerically conducted to investigate the flame structure and NO emission characteristics in a non-premixed counterflow flame of blended fuel of
. The combination of
, and Ar as fuel is selected to clearly display the contribution of hydrocarbon products to flame structure and NO emission characteristics due to the breakdown of
. Radiative heat loss term is involved to correctly describe the flame dynamics especially at low strain rates. All mechanisms including thermal,
, and Fenimore are also taken into account to separately evaluate the effects of
addition on NO emission characteristics. The increase of added
quantity causes flame temperature to fall since at high strain rates diluent effect is prevailing and at low strain rates the breakdown of
produces relatively populous hydrocarbon products and thus the existence of hydrocarbon products inhibits chain branching. It is also found that the ratio of the contribution by Fenimore mechanism to that by thermal mechanism in the total mole production rate becomes much larger with increase in the
quantity and strain rate, even though the absolute quantity of NO production is deceased. Consequently, as strain rate and
quantity increase, NO production by Fenimore mechanism is remarkably augmented.
Development of Experimental System for Automotive Electrical Circuit in Technical High School
Lee, Yong-Ju ; Seo, Young-Dal ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 154~160
The experimental system, developed in this research, is a teaching material that trains and practices automobile electric circuit in technical high school. This system consists of a textbook, 15 kinds of instruments and 62 kinds of 'Flash' animations. Textbook includes automobile electric circuits and experimental process. Instruments have 23 kinds of drills. Its is composed of electrical relays, motors, switches, light bulbs, electrical lines and power unit so on. 'Flash' animation displays an electrical current flow on circuits actually. Both Dacum method and ISD skill have been conducted to analysis job and design syllabus. The experimental system have been implemented on technical high school class to evaluate its objectivity and effect. It is expected that this system can contribute to studying of car service.
A Study on Vehicle Steering Feel Using Objective Measurement
Kim, Jung-Sik ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 161~170
As one of the major handling performances of the vehicle and tire, the steering feel is very important in the high speed where safety and refinement is a major concern for the drivers. This paper presents both subjective and objective techniques for the assessment of the steering feel including the on-center feel and steering response. For this, subjective evaluation method of the steering feel was studied at first and then objective parameters were selected by considering the process by which the steering feel is evaluated subjectively. From statistical analysis of subjective and objective data for the several vehicles and professional drivers, it was found that the subjective assessment of the steering feel could be successfully explained by means of the suggested objective parameters. Also, the main objective parameters related to the subjective assessment of the steering feel could be found.
An Evaluation Method of Fracture Toughness on Interface Crack in Friction Welded Dissimilar Materials
Chung, Nam-Yong ; Park, Cheol-Hee ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 171~177
In this paper, an evaluation method of fracture toughness on interface cracks was investigated in friction welded dissimilar materials with interfacial edge cracks. To establish a reasonable strength evaluation method and fracture criterion, it is necessary to analyze stress intensity factor under the load and residual stress condition on friction welded interface between dissimilar materials. The friction welded specimens with an edged crack were prepared for analysis of stress intensity by using the boundary element method (BEM) and the fracture toughness. A quantitative fracture criterion for friction welded STS 304/SM 45C with interface crack is suggested by using stress intensity factor, F and the results of fracture toughness experiment.
Improvement of Emission Performance in a 3.3 Liter DI Diesel Engine by Using Dimethyl Ether Fuel
Pyo, Young-Dug ; Lee, Young-Jae ; Kim, Mun-Heon ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 178~185
A study is improvement of power and emission in a inline-pump Dr diesel engine by using Dimethyl ether Fuel. Dimethyl ether (DME) is an oxygenated fuel with a cetane number higher than that of diesel oil. It meets the ULEV emission regulation and reduces the smoke to almost zero when used in a diesel engine. But NOx emission is almost same and CO, THC emissions are lower than that of diesel engine. The emissions aren't satisfied the stronger emission regulation in the further. Generally DOC (Diesel Oxidation Catalyst) is used to reduce CO & THC emissions and EGR (Exhaust Gas Recirculation) system is used to reduce NOx emission. Test results showed that the torque and the power with DME were almost same as those of pure diesel oil, but the brake thermal efficiency increased a little. also the BSEC (Brake Specific Energy Consumption) with DME was similar that of diesel. The test results showed that the DOC was the vary effective method to reduce the CO emission in case of Dimethyl Ether Fuel in diesel engine. But, THC emission is showed a little reduction rates. Also EGR system was the very effective method to reduce the NOx emission in case of Dimethyl Ether Fuel in diesel engine.
The Effects of the Combustion Characteristics on the Exhaust System Volume of the SI Engine in Idling
Noh, Hyung-Chul ; Park, Kyoung-Suk ; Son, Sung-Man ;
Transactions of the Korean Society of Automotive Engineers, volume 15, issue 4, 2007, Pages 186~192
We research into the exhaust system volume what proving the optimum exhaust performance and combustion characteristics. Many automobile manufactures have developed complex exhaust system for environment regulation and noise reduction. This complex exhaust system provides acoustics silencing and low frequency noise for customers demand. Recently, automobile exhaust system have made the Dual muffler concerning to the noise and vibration reduction. Also it bring the engine performance down by decreasing the back pressure and temperature in the exhaust system. The experiments are carried out different volume of exhaust system. In order to establish the optimized conditions design factors which are taking exhaust system volume, it show how the exhaust performance influence on the engine performance in idling.