Residual Gas Fraction Research Articles

Turbocharged DISI engine low-load performance improvement investigation through ozone seeding with residual gases and excess air charge dilution

The automotive industry has long prioritized the search for more efficient engines, driven by environmental concerns, fuel prices, and consumer demand for fuel-efficient vehicles. Various technologies and strategies are explored to enhance performance while reducing fuel consumption and emissions. Despite potential combustion stability issues, techniques like using lean mixtures or retaining exhaust gases are commonly employed. Ozone seeding has emerged as a combustion enhancer for internal combustion engines, particularly effective under lean mixtures or high residual gas levels, aiming to stabilize de-throttling conditions, minimize pumping losses, and enhance engine efficiency by enhancing the reactivity of the mixture through the release of radicals that facilitate fuel oxidation. This study investigates the impact of ozone addition on engine performance, emissions, and fuel consumption using a turbocharged SI vehicular engine on a dynamometer bench under different loads. Ozone was introduced to the engine intake using an ozone generator with compressed air, considering two mixture dilution strategies: fresh air and residual gases. Results show that ozone application, with Brazilian Gasoline Type C, induces autoignition of the end-gas under specific low-load, low-engine speed conditions. Up to 1000 ppm, ozone has no discernible impact on DISI engine operation under excess air dilution, maintaining performance equivalent to the baseline. For specific operating conditions with 3 and 4 bar BMEP, where ozone stabilizes combustion with higher residual gas fraction (RGF) percentages, there is a notable reduction in specific fuel consumption, suggesting a potential 1%–1.5% increase in brake efficiency. However, ozone seeding with high RGF percentages leads to a slight increase in CO emissions, elevated NOX emissions, and a tendency to reduce THC emissions up to a certain RGF limit.

Effects of exhaust gas recirculation on nitrogen oxides, brake torque and efficiency in a hydrogen direct injection spark ignition engine

This study investigated the effects of exhaust gas recirculation (EGR) on emission and efficiency in a hydrogen direct injection spark ignition engine. EGR was supplied as the low-pressure (LP)-EGR system by controlling EGR valve from zero to 18.7% in terms of mass fraction. The result showed that EGR effect on nitrogen oxides (NOx) reduction became enlarged as higher engine speed due to increasing residual gas fraction. Also, under the same excessive air ratio (λ:2.2), EGR addition made NOx reduction from 89.9 to 98.7 % as varying engine speed. As NOx limit was low, the maximum brake torque was also reduced. However, by using appropriate EGR, NOx margin could be converted to increasing brake torque under the same NOx concentration level from 1.9% to 18.2% as varying engine speeds. From this result, to achieve the maximum output when reaching the turbocharger’s limit in a hydrogen engine and effectively reduce nitrogen oxide emissions, it is not only dependent on lean combustion but also effective to incorporate approximately 20% EGR into the operating strategy.

Combustion stability, RGF and pressure referencing effect on HRR for a high compression ratio SI engine with natural gas lean mixtures

The knocking and heat release based on cylinder pressure trace is a widespread practice in combustion diagnostic for conventional SI engines. The accuracy depends on quality of measured in-cylinder pressure, thermodynamic models and parameters feeding such models. In non-conventional engine, common models to assess engine operation, do not satisfy properly expected standard, thus application of new methods and models is required. This study presents the determination of knocking intensity by in-cylinder pressure and cycle-to-cycle variability for operation analysis, the effect of referencing pressure and residual gas fraction on heat release for non-conventional SI engines with high compression ratio with natural gas at partial loads and lean mixture. Higher spark timings was achieved at 21 degrees, limited by low occurrence audible knock for KI20 over 0.04 bar. Compression ratio 15.5, engine speed at 1800 rpm, air-cooled system, and equivalence ratio of 0.73 make limited the operation. KI20 of 0.072 was reached at IMEP 3.96 bar and spark timing of 21 degrees. Maximum CoV of KI20 was 27.1. Pressure referencing shows low differences in polytropic coefficients of 1.34. Slight difference for RGF generates differences in the mass burned up to 12%, and around 0.4 degrees in combustion duration.

Potential of ozone addition on dethrottling of a gasoline/ethanol blend-fueled direct injection spark ignition engine in part load

Several efforts are required to improve engine efficiency and decrease global carbon dioxide (CO2) emissions and local pollutant products. In countries like Brazil, with a four-decade long experience with ethanol, the use of fossil fuels, although widespread, is being put under intense scrutiny. Governmental programs like ROTA 2030 stimulate engine research and development focused on environment-friendly fuels such as bioethanol-gasoline blends. Brazilian gasoline has about a quarter of ethanol, reducing the carbon footprint while maintaining suitable energy density. Regardless of the fuel, the load control method in part load operation of spark ignition engine causes a considerable penalty in fuel conversion efficiency. For these reasons, ozone addition was tested as an ignition enhancer that would allow higher de-throttling to reduce part-load pumping losses. The residual gas was used to dilute the mixture due to the possibility of keeping the three-way catalyst working properly with the stoichiometric mixture. An experimental investigation on efficiency, emissions and combustion related parameters was carried out in a downsized 1.0 l turbocharged direct-injected engine. Experimental tests were performed at 3 bar of indicated mean effective pressure (IMEP), 1500 rpm and stoichiometric air-fuel ratio. Spark timing (ST) was adjusted to achieve maximum indicated efficiency and the fuel used was Brazilian gasoline. Different ozone concentrations were used as a mixture with the intake air to overcome unstable engine operation by enhancing ignition. The results showed that it is possible to increase the gas exchange efficiency with ozone addition by promoting de-throttling operation with residual gases. Furthermore, the ozone addition exhibits the potential to promote autoignition of the end gas with spark assistance, even with a low compression ratio and residual gas fraction higher than 30%. However, the combustion efficiency is impaired by the higher residual gas fraction in some operation points that leave room for improvements.

Physics-based modeling of homogeneous charge compression ignition engines with exhaust throttling

Homogeneous charge compression ignition (HCCI) engines create a more efficient power source for either stationary power generators or automotive applications. Due to the absence of direct actuation of ignition, HCCI based combustion control is quite challenging. For the purpose of control synthesis and design, a crank-angle based dynamic model of an HCCI engine with internal exhaust gas recirculation (EGR) is proposed in this paper. The HCCI autoignition timing is controlled by the amount of internal EGR induced by the cost effective exhaust throttling strategy. The zero dimensional single zone model is developed based on conservation of mass and energy and ideal gas law. The model is comprised of five subsystems: cylinder volume, intake, and exhaust runners along with combustion and heat-transfer models. Inputs to the model include engine speed, intake temperature, fueling rate, intake, and exhaust throttle positions. Outputs of the model contain the pressure, temperature, mass and burned gas fraction in the intake, exhaust and cylinder, air-to-fuel ratio (AFR), heat release rate, combustion phasing, and the indicated mean effective pressure (IMEP). The model is developed based on MATLAB/Simulink and validated against experimental data under steady-state and transient conditions at various intake temperatures, fueling levels, and exhaust throttle positions. Results demonstrate that by changing the exhaust throttle position, the pressure in the exhaust runner is regulated. As a result, the residual gas fraction is altered, leading to changes in mixture temperature and thus control of the HCCI combustion phasing. In the end, closed loop simulation is conducted with a linear quadratic Gaussian (LQG) controller applied to the crank-angle based model for regulation of combustion timing CA50 using exhaust throttle during load (fueling level) changes. In the future, this model can be utilized for control development and hardware in the loop (HIL) simulation.

The message of oldhamites from enstatite chondrites

We have determined rare-earth element (REE) abundances in oldhamites (CaS) from 13 unequilibrated and equilibrated enstatite chondrites (5 EH and 8 EL) and in a few enstatites by in situ, laser ablation ICP-MS. In EH chondrites, oldhamite REE patterns vary from the most primitive petrographic types (EH3) to the most metamorphosed types (EH5). In EH3, CI-normalized REE patterns are convex downward with strong positive Eu and Yb anomalies, whereas EH5 display flat patterns with enrichments reaching about 80 times CI abundances. The positive anomalies of Eu and Yb found in oldhamites of primitive EH chondrites indicate that they represent the condensation of a residual gas fraction, in a manner similar to fine-grained CAIs of carbonaceous chondrites. The early condensate may have been preserved in the matrix of unequilibrated EH. Equilibrated EH oldhamite patterns may result from metamorphic evolution and REE redistribution on the EH parent body. On the contrary, all the oldhamites from EL chondrites (EL3 to EL6) display a single kind of patterns, which is convex upward and is about 100 times enriched relative to CI, with a negative Eu anomaly. In addition, the EL pattern is similar to that of oldhamites from aubrites (enstatite achondrites). The latter observation suggests that oldhamites of all EL metamorphic types (including primitive ones) bear the signature of a magmatic event accompanied by FeS loss as vapor, prior to the assembly of the EL parent body. Given the difficulty of obtaining precise ages on enstatite chondrites, it is not possible to discuss the chronology of the events recorded by the oldhamite REE patterns.

Prediction of knock propensity using stochastic modeling in a spark-ignition engine

To comply with stringent CO2 regulations, enhanced thermal efficiency has been prioritized in internal combustion engine development; however, this has strongly driven the development of engines with operating conditions more prone to knock. Current knock sensors have its limitations to decompose knock signal by degradation so that it required a cross-referencing signal. In addition, knock control intervention is currently preceded by the occurrence of the knock, leading to decrease in thermal efficiency by retarding spark timing. In the present work, a novel prediction model for knock propensity (incidence) is presented, aiming to enable active control of knock or autoignition, and to support conventional knock sensor for cross-referencing by facilitating virtual knock sensor. A zero-dimensional model-based prediction of the in-cylinder pressure is demonstrated to prevent using in-cylinder pressure transducer, along with other incorporated predictive sub-models for the residual gas fraction, heat loss, burn duration, and heat release rate. Ignition delay correlation and Livengood-Wu relation are used to predict the onset of knock, and a burn point-based criterion is newly proposed for application in stochastic modeling for determining the knock propensity. The predicted knock propensity from the combined holistic model shows a remarkable agreement with experimental results.

Exergy evaluation of equivalence ratio, compression ratio and residual gas effects in variable compression ratio spark-ignition engine using quasi-dimensional combustion modeling

This study is founded on previously validated, in-house, comprehensive, two-zone, quasi-dimensional combustion model, predicting performance and emissions in spark-ignition engines. The model is extended to include exergy terms complementing the first-law analysis results, which provide further useful information by implementation on test results acquired from an experimental, Ricardo E6, variable compression ratio (VCR) gasoline engine at the authors’ laboratory, operated under various CR and equivalence ratio (EQR) values at wide-open throttle. The model consists of unburned and burned zones simulating the combustion process, following strictly the flame-front movement in combustion chamber. The eventual combustion of the unburned mixture turbulent entrainment into burned zone through the flame-front area is followed closely. The exergy terms of each simulated zone are identified and computed, considering also chemical exergy components (diffusion plus reactive). The accurate account of temperature and species histories in burned zone after entrainment from the unburned one, should lead to more precise evaluation. This is important if irreversibility is computed from balance of all other exergy terms. The investigation examines and compares exergy-wise various EQR, CR and residual gas fractions. Presented diagrams of exergy terms for each zone and cylinder charge provide detailed information for chemical exergy, irreversibility and exergy losses.

Effects of Dilution and Flammability Changes on Mixture Reactivity in a Natural Gas Internal Combustion Engine

ABSTRACT Changes in the flammability characteristics of a combusting mixture and its ‘dilution’ levels – characterized, respectively, by the mixture’s equivalence ratio and residual gas fraction – can have significant impacts on the nature of combustion in internal combustion engines. These combustion changes can manifest as variations in combustion phasing and repeatability, and affect engine efficiency, emissions, and performance. The current work uses experimental, high-speed, in-cylinder CO2 concentration data from a single-cylinder, natural gas-fueled engine to track compositional variations in the combusting mixture; and then uses a chemical kinetics solver to isolate the effects of flammability and dilution changes on the mixture’s ‘reactivity,’ which is characterized by its laminar flame speed (LFS) and ignition delay (ID). It is found that LFS changes are driven strongly by the trapped equivalence ratio, while ID changes are driven primarily by dilution and pressure changes. Additionally, the effects of LFS changes on the overall combustion phasing are found to be more pronounced than those from ID changes, as the former influences both the combustion initiation and propagation processes.

Effect of the novel continuous variable compression ratio (CVCR) configuration coupled with spark assisted induced ignition (SAII) combustion mode on the performance behavior of the spark ignition engine

The paradox of low efficiency and high fuel consumption at low-load and high efficiency and knocking combustion at high-load are pushing the engine community to optimize compression ratio (CR) in the spark ignition (SI) engine. However, it is difficult to balance the performance under a wide load range with using a fixed CR. In this paper, a novel continuous variable compression ratio (CVCR) system was proposed and successfully used in a SI engine, which could continuously change the auxiliary combustion chamber volume, thereby achieving different compression ratios from 10.0:1 to 17.8:1. The results indicated that the total mass of residual exhaust gas in the cylinder of the engine equipped with CVCR system was increased, and the residual gas fraction (RGF) in the auxiliary cylinder was increased, while the RGF in the main cylinder wasn’t changed dramatically with increasing CR. In addition, combustion rate was increased and combustion duration was decreased with increasing CR. The heat transfer rate and its percentage in the total fuel energy was decreased with the increase of the CR. The BSFC and effective thermal efficiency of the engine equipped with CVCR system could be improved by 15.85% and 15.57% by adopting CR 17.8:1 and 10% external EGR under the operating condition of 2000 r/min and BMEP 9.59 bar, respectively. However, the intensity of knocking combustion was increased with CR and limited the utilization of the high CR in the SI engine. Using external exhaust gas recirculation strategy could greatly alleviate the knocking combustion and reduced the heat transfer rate through the combustion chamber wall, which was beneficial to increase the indicated thermal efficiency and adiabatic efficiency.

Machine Learning Integration With Combustion Physics to Develop a Composite Predictive Model for Reactivity Controlled Compression Ignition Engine

Abstract Phasing of combustion metrics close to the optimum values across operation range is necessary to avail benefits of reactivity controlled compression ignition (RCCI) engines. Parameters like start of combustion occurrence crank angle (CA) (θsoc), occurrence of burn rate fraction reaching 50% (θ50), mean effective pressure from indicator diagram (IMEP), etc. are described as combustion metrics. These metrics act as markers for the macroscopic state of combustion. Control of these metrics in RCCI engine is relatively complex due to the nature of ignition. As direct combustion control is challenging, alternative methods like combustion physics-derived models are a subject of research interest. In this work, a composite predictive model was proposed by integrating trained random forest (RF) machine learning and artificial neural networks (ANNs) to combustion physics-derived modified Livengood–Wu integral, parametrized double-Wiebe function, autoignition front propagation speed-based correlations, and residual gas fraction model. The RF machine learning established a correlative relationship between physics-based model coefficients and engine operating condition. The ANN developed a similar correlation between residual gas fraction parameters and engine operating condition. The composite model was deployed for the predictions of θsoc, θ50, and IMEP as RCCI engine combustion metrics. Experimental validation showed an error standard deviation (σ68.3,err) of 0.67°CA, 1.19°CA, 0.223 bar and symmetric mean absolute percentage error of 6.92%, 7.87%, and 4.01% for the predictions of θsoc, θ50, and IMEP, respectively, on cycle to cycle basis. Wide range applicability, lesser experiments for model calibration, low computational costs, and utility for control applications were the benefits of the proposed predictive model.

Evaluation of residual gas fraction estimation methods for cycle-to-cycle combustion variability analysis and modeling

Cycle-to-cycle combustion variability in spark-ignition engines during normal operation is mainly caused by random perturbations of the in-cylinder conditions such as the flow velocity field, homogeneity of the air-fuel distribution, spark energy discharge, and turbulence intensity of the flame front. Such perturbations translate into the variability of the energy released observed at the end of the combustion process. During normal operating conditions, the cycle-to-cycle variability (CCV) of the energy release behaves as random uncorrelated noise. However, during diluted combustion, in either the form of exhaust gas recirculation (EGR) or excess air (lean operation), the CCV tends to increase as dilution increases. Moreover, when the ignition limit is reached at high dilution levels, the combustion CCV is exacerbated by sporadic occurrences of incomplete combustion events, and the uncorrelation assumption no longer holds. The low or null energy released by partial burns and misfires has an impact on the following combustion event due to the residual gas that carries burned and unburned gases, which contributes to the deterministic coupling between engine cycles. Many residual gas fraction estimation methods, however, only address the nominal case where complete combustion occurs and combustion events are uncorrelated. This study evaluates the efficacy of such methods on capturing the effects of partial burns and misfires on the residual gas estimate for high-EGR operation. The advantages and disadvantages of each method are discussed based on their ability to generate cycle-to-cycle estimates. Finally, a comparison between the different estimation techniques is presented based on their usefulness for control-oriented modeling.

Model-based residual gas fraction control with spark advance optimization

Abstract Residual gas fraction and combustion phase are two important variables in spark ignition engines since affect thermal efficiency, emissions and combustion stability. In-cylinder pressure sensors are the most extended signal used as feedback for closed-loop spark advance and residual gas fraction control. However, pressure sensors are still affected by challenges such as durability and cost. This work presents a model-based residual gas fraction control with spark advance optimization. The controller is validated in a light-duty spark ignition engine, being able to control the residuals both in steady and transient conditions, showing the potential to replace in-cylinder pressure sensors.

Novel strategies to overcome the limitations of a low compression ratio light duty diesel engine

Low compression ratio (LCR) approach in diesel engines can reduce the oxides of nitrogen (NOx) and soot emissions simultaneously owing to lower temperatures and longer fuel-air premixing time. The present work investigates the effects of lowering the geometric compression ratio (CR) from 18:1 to 14:1 in a naturally aspirated (NA) single cylinder common rail direct injection (CRDI) diesel engine. Based on the investigations done across the entire speed and load range, significant benefits were observed in the NOx and soot emissions. However, lowering the compression ratio had adverse effects on brake specific fuel consumption (BSFC), unburned hydrocarbon (HC) and carbon monoxide (CO) emissions, especially at low-load and high-speed operating points. To overcome these limitations, novel strategies including split-cooling system (SCS) and secondary exhaust valve opening (SEVO) are proposed in the present work. While the fuel injection parameters optimization specific to LCR could help to improve the BSFC, HC and CO emissions penalty to a reasonable extent, the SCS concept can provide further benefits by reducing the heat loss to coolant and improving the engine component temperatures. Increasing the residual gas fraction using the optimized SEVO concept could further improve the charge temperature leading to a further reduction in the BSFC, HC and CO emissions. The net benefits of the optimized LCR approach are quantified for the modified Indian drive cycle (MIDC) using a one-dimensional simulation tool. The results obtained show a signification reduction of 22% and 74% in NOx and soot emissions respectively as compared to the base 18 CR engine results. Moreover, the penalty in HC and CO emissions could be contained to a large extent resulting in only a slight penalty of 23% and 20% respectively. Furthermore, the higher BSFC with the LCR approach could be successfully addressed and the final values were found to be better than the stock compression ratio by 1.5%. Overall, the strategies proposed in the present work are found to be beneficial to develop modern diesel engines in compliance with the future emission regulations which demand extreme control on NOx and soot emissions.

An assessment of the availability and efficiency of a gasoline fueled spark ignition internal combustion engine

ABSTRACT The energy losses of engines are usually estimated based on the first law of thermodynamics; however, it is incapable to reveal the quality of these losses. In this framework, the engagement of second law analysis (availability) has become progressively attractive. This paper aims to thermodynamically assess the availability and efficiency of a gasoline spark ignition internal combustion engine. For this purpose, a new subroutine of the second law of thermodynamic model was incorporated with an adapted program of the first law of thermodynamic model, which was formerly developed based on the two-zone combustion hypothesis. Details of an experimental setup were employed for model buildup. The measured results were adopted for model validation. In terms of the first law analysis, the modified model was well matched with the experimental observation of the in-cylinder pressure trend. In addition to influence of equivalence ratio and engine speed, analysis was performed to consider not extensively assessed parameters, namely, the combustion duration and residual gas fraction. The results showed that the stoichiometric condition (ϕ = 1) gave the best trends of the availability components. While, these trends were deteriorated as the combustion duration extended, and the residual gas fraction increased. In terms of availability distribution, its lost with exhaust gases was the highest one for all investigated parameters. Furthermore, the medium engine speed, 2000 rpm for current study, was nominated as the optimum operating condition. Maximum levels of engine efficiencies obtained for the first and second laws analyses were about 47.574% and 43.728%, respectively. The developed model can be extending for further evaluation in terms of alternative fuels aspect.

Exergy-based performance analysis and evaluation of a dual-diesel cycle engine

Performance examinations of a dual-Diesel cycle engine in point of engine performance characteristics such as exergy efficiency, power and power density have been conducted. The effect of design parameters of the engine cycle such as intake temperature, intake pressure, piston friction coefficient, average piston velocity, engine revolution, stroke length, residual gas fraction, engine pressure ratio, engine temperature ratio, compression ratio, ratio of bore diameter to stroke length, and equivalence ratio, on the performance characteristics are evaluated by considering variable specific heats and irreversibilities resulting from exhaust output, heat transfer, incomplete combustion and friction. The results can provide substantial information researchers who study on dual-Diesel cycle engine design and manufacture.

Taguchi‐Grey and ANOVA optimization techniques for engine performance with water in diesel emulsion fuels

AbstractIn the current study, optimization of the performance parameters like effective power (EP), effective power density (EPD), effective efficiency (EE), and different heat losses with respect to six engine control parameters, that is, emulsion fuel, compression ratio, equivalence ratio, engine speed, residual gas fraction, and fuel injection pressure with three levels of each, were performed. Taguchi method is used to design the L27 orthogonal array, using Minitab17 software. Optimization of individual performance parameters is performed with the signal to noise ratio curve, and Grey analysis is used to optimize the overall output performance parameters. Furthermore, an analysis of variance method is investigated to calculate the contribution percentage of control parameters. The theoretical analysis revealed that the overall optimum response of output parameters is found with 10% blend of water (A3), 18 compression ratio (B3), 0.8 equivalence ratio (C1), 2100 rpm engine speed (D3), 10% residual gas fraction (E3), and 100 kPa fuel injection pressure (F1). The EP and EPD are improved by 9.6% and 9.19%, respectively. Also, an average GRG for optimum response setting coincides with the average GRG value of the initial setting. The resulted optimization models are anticipated to be positive instruction for diesel engine operating parameters.

Prediction of Fuel Maps in Variable Valve Timing Spark Ignited Gasoline Engines Using Kriging Metamodels

<div class="section abstract"><div class="htmlview paragraph">Creating a fuel map for simulation of an engine with Variable Valve Actuation (VVA) can be computationally demanding. Design of Experiments (DOE) and metamodeling is one way to address this issue. In this paper, we introduce a sequential process to generate an engine fuel map using Kriging metamodels which account for different engine characteristics such as load and fuel consumption at different operating conditions. The generated map predicts engine output parameters such as fuel rate and load. We first create metamodels to accurately predict the Brake Mean Effective Pressure (BMEP), fuel rate, Residual Gas Fraction (RGF) and CA50 (Crank Angle for 50% Heat Release after top dead center). The last two quantities are used to ensure acceptable combustion. The metamodels are created sequentially to ensure acceptable accuracy is achieved with a small number of simulations. Two optimization problems are then solved using the developed metamodels, for full load and part load conditions, respectively. We demonstrate that the estimated fuel map is of high accuracy compared to the actual map. The map is obtained with about one tenth of the number of engine simulations for a full factorial design, leading to much faster predictions.</div></div>

Performance analysis of a novel six-stroke Otto cycle engine

In this study, a simulation model with finite time thermodynamics was presented for an Otto cycle six-stroke engine. In this six-stroke engine, two free strokes occur after the exhaust stroke. These free strokes cause the engine to have higher thermal efficiency. Due to high thermal efficiency, these six-stroke engines can be used in hybrid electric vehicles. In this study, the effect of residual gas fraction and stroke ratio on the effective power and effective thermal efficiency were investigated. In addition, heat balance was obtained for the engine and the use of fuel energy in the engine was examined with the help of performance fractions. In the simulation model, the results are quite realistic as the working fluid was assumed to consist of fuel-air-residual gases mixture.

Comparative Study of the Effective Release Energy, Residual Gas Fraction, and Emission Characteristics with Various Valve Port Diameter-Bore Ratios (VPD/B) of a Four-Stroke Spark Ignition Engine

In this research, the residual gas, peak firing pressure increase, and effective release energy were completely investigated. To obtain this target, the experimental system is installed with a dynamo system and a simulation model was setup. Through combined experimental and simulation methods, the drawbacks of the hardware optimization method were eliminated. The results of the research show that the valve port diameter-bore ratio (VPD/B) has a significant effect on the residual gas, peak firing pressure increase, and effective release energy of a four-stroke spark ignition engine. In this research, the engine was performed at 3000 rpm and full load condition. Following increased IPD/B ratio of 0.3–0.5. The intake port and exhaust port diameter has a contrary effect on engine volumetric efficiency, the residual gas ratio increase 27.3% with larger intake port and decrease 18.6% with larger exhaust port. The engine will perform optimal thermal efficiency when the trapped residual gas fraction ratio is from 13% to 14%. The maximum effective release energy was 0.45 kJ at 0.4 intake port-bore ratio, and 0.451 kJ at 0.35 exhaust port-bore ratio. The NOx emission increases until achieved a maximum value after that decrease even VPD/B was still increasing. With a VPD/B ratio of 0.35 to 0.4, the engine works without the misfiring.