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In this study, the impact of engine control parameters on combustion behaviors and particle number emissions was investigated with a spark ignition direct injection (SIDI) engine used various gasoline-ethanol blended fuels. The SIDI engine was tested with the E0, E30 and E85 at a engine operation of 1500 rpm/1.5 BMEP. The combustion pressure and mass burn fraction (MBF) according to the control parameters and ethanol fractions were analyzed. To verify the PN oxidation characteristics of the ethanol blended fuels, the size-resolved PN emissions over the three-way catalyst (TWC) were determined with a DMS500. The peak pressure in the cylinder was similar regardless of the type of fuel and the particle emissions were reduced by 92 % compared to gasoline at the engine out position in the E85 fuel. The results show that gasoline-ethanol blends have potential as alternative fuels and are effective in reducing the particle emissions in internal combustion engines.

Worldwide regulations on particulate matter for passenger vehicles have become stricter in recent years, which makes it difficult to satisfy for gasoline direct injection (GDI) vehicles. In this study, the level of reduction efficiency of particle emissions with a metal-foam gasoline particulate filter (GPF) for the turbocharged GDI vehicle was evaluated in the federal test procedure (FTP)-75 mode operation. The particle number (PN) emissions were analyzed using the AVL particle counter (APC) and fast response differential mobility spectrometer (DMS500) for particle size distribution. The PN concentration from the base GDI vehicle with only TWC is 1.64 E+12 number/km (#/km), while the value of the GPF-equipped case is 5.02 E+11 #/km with 69 % filtration efficiency in the vehicle test mode. In particular, the reduction rate of small particles under 23 nm in size was strongly improved with the additional installation of the metal-foam GPF. The maximum pressure drop through the GPF reached approximately 39 mbar at the highest acceleration point of phase 1 of the FTP-75 mode. The upstream temperature of the GPF was distributed at approximately 380 ∼ 510 oC in the vehicle test. The results show that the GPF-equipped GDI vehicle can satisfy the stringent particle regulation by Euro 6 in a straightforward manner.

Test flexibilities, such as the tire pressure, adjustment of brakes, vehicle preconditioning, test mass, and running-in period, are multiple factors that can confound vehicle emissions and fuel economy tests. The road load force is the most influential flexibility factor for a type-approval vehicle certification test. Because of these various factors, it was revealed that there was a substantial difference between the type-approval emissions and those from a real-driving emissions test. In this study, the test cycle road load energy using the road load coefficients determined by the TA coast-down procedure was the base condition. After calculating the test cycle road load power, the constant term of the road load coefficient was adjusted by the energy loss. The tolerance of the road load in domestic regulation is 15%, so the constant term of the road load coefficient was increased by 5% in the cycle road load energy loss. Then, the road load power and tractive power were calculated from the force and vehicle speed. The vehicle fuel efficiency, under the road load variation conditions, was determined for modern 2.4 L gasoline direct injection and lean NOxtrap-equipped diesel vehicles on a chassis dynamometer. To assess the impact of different road load values on the FE and carbon dioxide emissions, the test cycle was performed over the combined modes of the federal test procedure-75 and the highway fuel economy test. To investigate the road load variations of the vehicle fuel economy in correlation with the energy difference, the statistical approach of the one-way analysis of variance was applied. The results showed that the variations of the road load energy of the tested cycle were closely related in a trade-off relationship with the vehicle fuel economy.

Certified testing of motor vehicle driving resistance, fuel economy and emissions requires that the vehicle has reached the target distance specified for each country through running-in. In general, motor vehicles experience different tire wear and internal resistance profiles from their moving parts, including the brake, hub bearing, drive shaft and transmission, depending on how they have performed running-in over what range. This means that such differences can result in a discrepancy in the level of mechanical resistance that consists of tire rolling resistance and internal resistance. There is thus a potential impact on the fuel economy and emissions as tested by the chassis dynamometer. In this study, the nomenclatures define where the running-in testing takes place (“Location”), how the testing is performed (“Mode”) and over which distance the testing takes place (“Distance”) as the factors having the major impact on the mechanical resistance of a motor vehicle. Then the mechanical resistance was measured under different running-in distances using a chassis dynamometer and the determination was made on how the resistance decrease over the range to understand statistically how Location and Mode affect the reduction in mechanical resistance under different Distances. This study was also evaluated on which running-in test mode is the best for fuel economy and emissions certification through total cost analysis over the 6,500 km running-in distance. In addition, the process to identify the impact of vehicle running-in test conditions on the reduction in the mechanical resistance of the vehicle was suggested.

To meet greenhouse gas (GHG) emission target, automotive manufacturers should promote low carbon emission technology, including gasoline direct injection (GDI) systems. However, recent studies have shown that excessive levels of nanoparticles were emitted from GDI vehicles compared to port fuel injection (PFI) vehicles. One of the many ways to decrease nanoparticle emissions from GDI engine is to use alternative fuel This study used turbo charged 2.0 L 4-cylinder LPG direct injection engine (T-LPDi) that was converted from a turbo charged gasoline direct injection engine (T-GDI) with dedicated LPG fuel supply and control system. To analysis on combustion phenomena and nanoparticle emissions, in-cylinder pressure and exhaust gas were measured under engine dynamometer test. Additionally, various engine control parameters were swung to understand the effects of the control parameters on combustion and nanoparticle characteristics. Throughout this study, T-LPDi engine, compared to T-GDI engine, showed ∼ 9 % and 76 % reduction of CO2 and PN emissions respectively. By optimizing engine parameters based on parametric study, PN emissions were improved 70 % from the baseline of T-LPDi engine emissions.

As global warming and fine dust problem became issues, the regulation for relevant exhaust emissions has been strengthened gradually. Thus, a major challenge of automotive engineers is reducing the CO2 and particle emissions at the same time. Especially for gasoline direct injection (GDI) engines, which are widely used due to its higher fuel efficiency, an excessive particle emissions problem compared to port fuel injection system is the big nuisance. The LPG fuel, which has great fuel properties for applying this direct injection scheme, could deal with this. Also, downsized turbocharged system can reduce additional fuel consumption and CO2 emissions sequentially. In this study, a GDI passenger car and the same vehicle equipped with a downsized turbocharged liquefied petroleum gas direct injection (T-LPDi) engine were evaluated under chassis dynamometer test to verify the exhaust emission abatement capability of T-LPDi vehicle. The T-LPDi engine was developed for research use, which has dedicated fuel supply and control strategy for LPG fuel. Comparing the T-LPDi and GDI vehicles, the CO2 emissions were decreased by > 20% under the vehicle test condition, while particle number and mass emissions were decreased by > 90% and >50% from the T-LPDi vehicle respectively. These results showed a potential of T-LPDi concept as a good alternative with the environmental competitiveness, though there is room for further improvement of engine control and optimization of emission catalyst to meet more stringent future regulations.

Particle number (PN) emissions must be below 9.0 × 1011 #/km according to the Euro 6d regulation with a conformity factor (CF) of 1.5 during a real driving emissions (RDE) test, including the cold start phase. Thus, the object of this study is to analyze the on-road PN emissions characteristics under a cold start condition of a gasoline direct injection (GDI) vehicle depending on a catalytic stripper (CS), a gasoline particulate filter (GPF), the cold start phase, and the trip section using a corona charger type particle sensor, a CS, and an exhaust flow meter. Because the fuel-rich mode and retarded injection timing were applied to compensate for engine instability and caused incomplete combustion and deterioration of fuel vaporization during the cold start phase, PN emissions during the cold start phase accounted for a significant portion of the total PN. On-road PN emissions for the total trip were 2.71 × 1012 (without CS and GPF), 1.72 × 1012 (with CS and without GPF), 1.47 × 1012 (without CS and with GPF) and 9.50 × 1011 (with CS and GPF) #/km for cases A, B, C and D, respectively. The average CS effects on the decrease of PN emissions were 35.4% and 32.2% in the urban, 52.2% and 63.4% in the rural, 22.8% and 88.6% in the motorway, and 36.5% and 35.6% in the total trip sections without and with GPF, respectively. The average GPF effects on the reduction of PN emissions were 42.7% and 39.9% in the urban, 58.2% and 68.0% in the rural, 27.9% and 89.3% in the motorway, and 45.6% and 44.8% in the total trip sections without and with CS, respectively.

Since it is common for vehicles with idle engines to be stored indoors during the winter season to remain warm, better constraints are needed for idling emissions at low ambient temperature. CH4 (methane), C2H6 (ethane), C2H4 (ethylene), HNCO (isocyanic acid), N2O (nitrous oxide), NH3 (ammonia), C3H6 (propylene), and HCHO (formaldehyde) from many unregulated exhaust emissions were selected and measured by a Fourier Transform Infrared Spectroscopy (FTIR) analyzer in this study. This paper investigates the idling regulated and unregulated emissions of Euro 5/6 diesel vehicles at cold start and hot restart near 0 °C conditions. The impact of cold start and hot restart on NOx idling emissions was lower than CO and HC idling emissions in diesel vehicles. With regard to unregulated emissions, high fuel–air equivalence ratios and longer ignition delay in the idle cold start condition may increase incomplete combustion and affect the thermal cranking processes, leading to the increase of CH4, C2H4 and C3H6. Furthermore, as the formation of N2O is considerably affected by the equivalence ratio and cylinder temperature, a high fuel-air equivalence ratio at low ambient temperature in the cold start condition resulted in the increase of N2O emissions.

Although the chassis dynamometer type approval test considers real-world conditions, there are a few limitations to the experimental test environment that may affect gaseous or particulate emissions such as road conditions, traffic, decreasing tire pressure, or fluctuating ambient temperature. Furthermore, the real driving emission (RDE) test takes a long time, and it is too long to repeat under different experimental conditions. The National Institute of Environmental Research (NIER) test modes that reflect the driving pattern of Korea are not certification test modes, but can be used to evaluate the influence of traffic conditions because these modes consist of a total of 15 test modes that vary according to average speed. The use of the NIER #03, #09, and #13 modes as low-, medium-, and high-speed modes allow for gaseous and particulate emissions to be measured and analyzed. Additionally, the worldwide harmonized light-duty vehicle test procedure (WLTP), the certification mode of Europe, is used to test cycles to investigate the difference under cold- and hot-engine start conditions. The engine operating parameters are also measured to evaluate the relationships between the various test conditions and test cycles. The regulated and greenhouse gas levels decrease under various driving conditions, but the particle number (PN) emission level shows a different trend with gaseous emissions. While the PN and CO2 results dramatically increase when the air conditioner is on, tire pressure conditions show different PN size distributions: a large-sized PN fraction, which contains particles larger than 100 nm, increases and a sub-23 nm-sized PN fraction decreases. Under cold-start conditions in the WLTP modes, there are much higher PN emissions than that of an engine under hot-start conditions, and the sub-23-nm-sized PN fraction also increases.

This study investigated the effects of various ethanol-gasoline blends on the hazardous air pollutants (HAPs) emissions from a wall-guided direct injection passenger vehicle. The fuel economy (FE) as well as regulated and unregulated gaseous emissions was evaluated on a chassis dynamometer using the federal test procedure (FTP-75) mode. Five fuels with varying ethanol contents of E0, E10, E30, E50, and E85 were prepared by blending ethanol into commercial gasoline on a volumetric basis and were analyzed each fuel specification. The engine control schemes of fuel injection quantity for various ethanol blends were adjusted to optimize the engine starting capability, vehicle drivability and emissions performance. The FE of the E85 fueled vehicle decreased by 29% relative to gasoline fuel due to the low energy content of ethanol. Blending ethanol into gasoline produced a dramatic decrease of particulate emission, because pure ethanol has no aromatic compounds and carbon content lower than that of gasoline. As a result, nano-particles were rarely emitted in the vehicle tests of fuels with more than 30% ethanol. Carbonyl compounds emissions, which originate from partial oxidization or incomplete combustion of ethanol, also rose sharply as the ethanol content increased, while volatile organic compound (VOC) emissions were reduced considerably with medium- and high-ethanol formulations due to the lower proportion of aromatic components in these fuels.

Construction of harmful emission inventory from conventional and sustainable low carbon fueled vehicles is important issues to improve urban air quality and human health. In this study, the gaseous, nanoparticle, and unregulated gaseous emission formation behavior from a medium-duty minibus were investigated using the World Harmonized Vehicle Cycle (WHVC). The state-of-the-art diesel and turbocharged direct-injection liquefied petroleum gas (LPG) vehicle were tested on a chassis dynamometer. The after-treatment system of the 3.9-L diesel engine was composed of the DOC, DPF and SCR, which satisfy the Euro 6 emission regulation. The 3.3-L stoichiometric spark ignition direct injection LPG engine was a TWC-only system. The formation of harmful emission components from the light-duty minibus operation was closely related to powertrain types, combustion mechanisms, after-treatment devices, and physicochemical properties of the tested fuels. Additionally, the chemical composition and low heating value (or energy content) of the respective fuels substantially affected the vehicle CO2 emissions and fuel economy performance. Compared to LPG vehicle, the THC and NOx emissions from diesel vehicle were 63% and 511%. Similar PN concentrations were measured with each powertrain, but 2–3 times higher nucleation mode particles were released with diesel vehicle. Two vehicles showed comparable CO2 emissions, while fuel economy from diesel and LPG vehicle were 6.81 km/L and 4.60 km/L. The proportions of N2O and CH4 emissions with ozone forming potential (OFP) were 1.2% (diesel) and 0.3% (LPG), which showed the potential to mitigate the CO2-equivalent emissions from LPG minibus.

Euro 6-compliant diesel passenger cars have tended to feature lean NO x traps (LNTs) to satisfy the increasingly stringent NO x regulations. This paper focused on NO x emission characteristics by the NO x sensors installed at both before and after LNT from a Euro 6 diesel vehicle on a chassis dynamometer. The vehicle was repeatedly driven according to the new European driving cycle (NEDC) and the world-harmonized light-duty vehicle test cycle (WLTC) at various ambient temperatures (23, 14 and −5 °C). LNT regeneration was detected twice in the NEDC but 5 times in the WLTC due to the longer period, increased mileage and more frequent acceleration in the WLTC. Accordingly, the NO x conversion rate was higher, and the NO x emission factor was lower for the NEDC than for the WLTC. Additionally, as the ambient temperature decreased, the NO x concentration increased considerably. Because of the poor mixing of fuel and air and the reduced combustion efficiency and stability, the exhaust gas recirculation (EGR) rates decreased. Because the LNT did not reach the light-off temperature (LOT) in the cold start phase, the chemical reactions in the LNT did not occur, and only NO was detected. For the LNT regeneration process, the EGR rates decreased, and the fuel rates increased to release the stored NO x in the LNT. The emissions characteristics of the products, such as NO, NO 2 , N 2 O and NH 3 , during regeneration varied depending on the stored NO x , the after-treatment temperature, and the vehicle driving condition. The results from this comparative study can contribute to monitoring the NO x emission characteristics and optimizing the engine management system to meet future emission regulations including WLTC and low ambient temperature conditions.

In this study, the regulated, particulate, and unregulated emissions, and the fuel economy (FE) from a direct injection spark ignition (DISI) vehicle were investigated on a chassis dynamometer. Two vehicle test cycles, the congested urban (NIER03) and rural modes (NIER09), which reflect vehicle driving patterns in Korea, were tested with varying ethanol contents of gasoline (E0), and low- (E10), medium- (E30 and E50), and high-ethanol blended fuels (E85). The particle number (PN) concentration from E0 was substantially reduced by one or two orders of magnitude with medium- or high-ethanol blended fuels, respectively. The E10 fuel showed the highest PN concentration because of the physicochemical mixture properties of the azeotropic characteristics. As the ethanol fraction increased, the particle sizes shifted to smaller sizes that were dependent on the vehicle test modes and oxygen proportions in the fuels. The regulated and unregulated emissions showed close relationships with the vehicle test modes and ethanol blends. Vehicle running with frequent idle-stops at an extremely low speed and dynamic transient driving under NIER03 showed higher BTEX emissions than the NIER09 mode, and produced lower emission levels due to the higher oxygen and lower aromatic proportions of the ethanol blends. Compared to the NIER03 mode, the CO2 emissions and FEs under the NIER09 mode were substantially improved, with a higher vehicle speed and more energy efficient engine operation points. The low energy contents of the E85 fuel resulted in slight increases in the CO2 emissions and reductions in the FEs of the NIER modes.

The nanoparticle emissions from gasoline direct-injection engines are of concern because of the high particle number concentrations compared with those from a gasoline port fuel injection engine. A gasoline particulate filter is a potential solution for reducing the particulate matter emissions. In this study, a 2.0 l turbocharged gasoline direct-injection vehicle with a metal-foam-type gasoline particulate filter was tested using the New European Driving Cycle and steady vehicle operating conditions. The particle number concentration, the particle-size distribution and the filtration efficiency were determined using a condensation particle counter and a fast response differential mobility spectrometer (DMS500). The particle number emissions (particle numbers per vehicle travelling distance (particles/km)) over the New European Driving Cycle were 1.95 × 1012 particles/km for a base vehicle equipped with a three-way catalytic converter and 5.68 × 1011 particles/km for the additional installation of a gasoline particulate filter on the base gasoline direct-injection vehicle. The filtration efficiency of the particle number and the particulate matter mass reached approximately 71% and 67% respectively. The nucleation-mode particles in the size range less than 23 nm for the gasoline direct-injection vehicle equipped with a three-way catalytic converter were further reduced on installation of a gasoline particulate filter at the downstream position of the three-way catalytic converter. A sharp pressure drop between the gasoline particulate filter of 21.0 mbar was obtained at a vehicle speed of 120 km/h in the New European Driving Cycle. The exhaust gas temperature before the gasoline particulate filter reached around 380–610 °C at steady vehicle speeds of 60–120 km/h. The installation of the gasoline particulate filter has the potential to satisfy the Euro 6c particle number emissions regulations for light-duty gasoline direct-injection vehicles.

Mobile source air toxic (MSAT) emissions from a direct injection spark ignition (DISI) passenger vehicle fueled with gasoline and liquid phase liquefied petroleum gas (LPG) were compared using a chassis dynamometer under several in-use vehicle driving conditions. For operation of a dedicated LPG-DI engine, low-pressure fuel systems were specially installed and various engine control parameters were recalibrated considering different chemical properties of LPG. A series of the National Institute of Environmental Research (NIER) modes for determining the emission factors of in-use vehicles in Korea were chosen to quantify not only the regulated emissions with particles but also the unregulated emissions of carbonyls, BTEX, and PAHs from a DISI light-duty vehicle (LDV) with gasoline and LPG. The regulated and particle emissions of LPG-DI vehicles showed strong reduction, and the proportions of sub-23 nm particles were 32–35% in gasoline and 50–65% in LPG. The results revealed that the levels of the MSAT emissions from a DISI engine were closely related to the driving patterns and the fuel properties. A substantial reduction of regulated emissions, particulates, BTEX, and particle-bound PAH emissions was achieved from a LPG-DI vehicle in real driving conditions. Carbonyl compounds acetaldehyde and acrolein showed significant increment from a LPG-DI vehicle.

This study was focused on experimental comparisons of the effects of various vehicle certification modes on the nano-particle and regulated emission characteristics of light duty vehicles with gasoline, diesel particulate filter (DPF) diesel, liquefied petroleum gas (LPG) and non-DPF diesel. The particulate matter, regulated emissions, and CO 2 emission of various fueled vehicles were analyzed with the golden particle measurement system, as recommended by the particle measurement program. The solid particles with a diameter above 23 nm, which in only non-volatile, were measured using a particle number counter (CPC). The vehicle tests were performed on the federal test procedure-75 (FTP-75) and the new European driving cycle (NEDC) mode, and the results were compared to evaluate particle formation with both CPC and a differential mobility spectrometer (DMS500). Particle formation was highly dependent on the vehicle speed and load conditions of each mode. In particular, the particle numbers of conventional fuels sharply increased during cold start, fast transient acceleration, and high-load operation phases of the vehicle emission tests. The DPF diesel vehicle fitted with a particulate filter showed substantial reduction of particulate matter whose number concentration was equivalent to those of gasoline and LPG fueled vehicles. It was found that particle emission and regulated emissions as well as CO 2 emission, and fuel economy were closely related with vehicle driving patterns and fuel composition, simultaneously. Finally, sub-23 nm nucleation mode particles using DMS500 were majority in the gasoline and LPG vehicles, whereas accumulation mode particles were mainly discharged in the diesel vehicles.

In this study, to evaluate the potential of a dedicated liquefied petroleum gas-direct injection (LPG-DI) vehicle, regulated and unregulated emissions from a light-duty gasoline direct injection (GDI) vehicle were compared. The vehicle tests were performed on a chassis dynamometer with constant volume sampler (CVS) over the federal test procedure (FTP)-75, highway fuel economy test (HWFET), and new European driving cycle (NEDC), which include the engine starting, transient and warm-up operation. The emissions of total hydrocarbon (THC) as well as nitrogen oxides (NOx) and nano-particles from the LPG-DI vehicle showed significantly superior performance relative to gasoline with excellent gaseous mixture preparation and low carbon fuel. The CO 2 emission of the LPG-DI vehicle decreased approximately 4–6% compared to the GDI vehicle. Aldehydes formation was influenced by vehicle test modes, such as the proportions of vehicle low speed patterns as well as long idle duration and the inclusion of engine warm-up periods. Formaldehyde, acetaldehyde, and acrolein compounds significantly increased with the LPG-DI vehicle, and this increase was related with partial oxidation during the combustion process of butane and propane. Except for the slightly increase in the HWFET mode, strong decreases in BTEX were observed with the application of LPG fuel in the FTP-75 and NEDC mode. It was found that the regulated and unregulated emissions were closely related to both the vehicle driving patterns and fuel compositions.

Lean NOx Trap (LNT) catalysts are capable of reducing exhaust NOx emissions from diesel engines. LNT stores NOx in lean condition and exhausts N2 by reducing NOx in rich condition. NOx reduction characteristic of LNT catalysts using throttle position sensor and fuel injection timing control for light-duty diesel engine was investigated. In contrast to SCR system, LNT catalyst uses diesel fuel in resuctant. Also if the concentration of reductant is exceeded, excessive amount of reductant will slip throughout LNT and cause another emission problem. Thus LNT regeneration with precise engine control established that can make higher NOx conversion efficiency and lower fuel penalty, prevent another emission problem. NOx and reductant concentration were measured by the NOx sensor and Mexa7100D equipped inlet and outlet of catalyst. As a result of engine test, regeneration strategy has reached high of 77.8% NOx conversion efficiency according to engine operation condition. Moreover, we have proved that it is possible to use regeneration strategy of LNT within 5% fuel penalty.

Cooled EGR system is widely used to reduce NOx emissions in diesel engine. But when EGR rate was increased, combustion stability was worsened and PM level was increased. So determining optimized control point of EGR rate is important. In order to determine this point, it is important to figure out the effect of EGR system on the exhaust emissions. In this research, NOx and PM emissions were analyzed with various coolant temperature supplied to the EGR cooler at several positions such as downstream of turbocharger, upstream and downstream of DPF. Effects of some variables such as EGR rate, hot / cooled EGR and change of injection timing were estimated. And CO 2 emissions were measured at exhaust and intake manifold to calculate EGR rate at each engine operating condition. Also combustion analysis was performed in each engine operating conditions. In the result of this study, there was trade-off between NOx emissions and PM emissions. When EGR rate was increased, combustion pressure was decreased and COV of IMEP was increased.

This study is mainly focused on the assessment of return, semi return, and returnless fuel supply system for an LPi engine. In order to compare the return type with returnless one with various LPG blends, combustion analysis and cyclic THC emission characteristic were tested at the part load operating condition of the LPi engine. Considering heat balance of each fuel supply systems, pressure and temperature increment of return type showed lower at the fuel rail during idle warm up operation. However, those of returnless type at LPG tank maintained stable and slow increment because the heat transfer from the LPi engine was minimized. Finally, hot restartability of each fuel supply systems were evaluated with the various LPG blends and fuel temperatures. As a result, semi return type has equivalent performance to return type considering combustion and emission characteristic, hot restartability performance for LPi engine. 1. 서 론 기존 믹서방식 연료공급시스템의 단점을 개선한 LPi(Liquid phase injection) 시스템은 LPG 탱크 내부에 장착된 연료펌프를 이용하여 LPG 연료를 가압 후 연료탱크의 토출부에서부터 인젝터까지 액체 상태를 유지한 다음 이를 전자식 인젝

In a gasoline SI engine, valve events and spark timings put forth a major influence on overall efficiency, fuel economy, and exhaust emissions. Residual gases controlled by the valve overlap can be used to reduce NOx emissions and the spark retardation technique can be used to improve raw THC emissions and catalyst light-off performance during the cold start phase. This paper investigated the behaviors of the engine and its combustion characteristics with various intake valve timings and spark timings during the fast idle condition and cold start. And cyclic THC and NOx emissions were measured at the exhaust port and their formation mechanisms were examined with fast response gas analyzers. As a result, THCs and NOx were reduced by 35% and 23% with optimizing valve overlap and spark advance during the cold transient start phase. Consequently, the valve events and ignition timings were found to significantly affect combustion phenomena and cold-start emissions.

The regulations for hydrocarbon emission from vehicles have become much more stringent in recent years. These more stringent regulations request vehicle manufacturers to develop the advanced exhaust system for reducing exhaust emissions. The exhaust emissions has many sources in vehicle. In order to investigate the characteristics of hydrocarbon(HC) in the exhaust manifold, concentrations of individual HC species were measured in exhaust process. Using sampling valve, the light hydrocarbon emissions were captured in the exhaust manifold(catalyst before and after) and analyzed from LPLi engine exhaust manifold(catalyst before and after) using different fuel properties. Then exhaust samples were measured by gas chromatography(GC) and exhaust gas analyzer. Catalyst conversion efficiency for fuel properties of Butane 100% was better than Propane 100%. Start delay of LPLi engine was observed as increment of propane contents in LPG fuels.

The air fuel ratios of current gasoline engines are almost controlled by several air flow meters. When CVVT (Continuous Variable Valve Timing) is applied to a gasoline engine for higher engine performance, the MAP (Manifold Absolute Pressure) sensor is difficult to follow the instantaneous air fuel ratio due to the valve timing effect. Therefore, a HFM (Hot Film Flow Meter) is widely used for measuring intake air flow in this case. However, the HFMs are incapable of indicating to reverse flow, the oscillation of intake air flow has an negative effect on the precision of the HFM. Consequently, the various duct configurations in front of the air flow sensor affect the precision of HFM sensitivity. This paper mainly focused on the analysis of the reverse flow, flow fluctuation in throttle upstream and the geometry of intake system which influence the HFM measurement.