Multi-cylinder Engine Research Articles

Environmental Sustainability Achievement on Diesel Engine Emissions Using Mahua Biodiesel Influenced by Graphite

Aims: To assess the performance and emission parameters of graphite-included mahua biodiesel at various proportions such as 10 ppm, 40 ppm, and 70 ppm. Background: The fuels derived from petroleum are harmful to the environment and deplete traditional energy sources. The discovery of alternative fuels has paved the way for various options. Studies suggest replacing diesel with vegetable oils. Neat vegetable oil has a high viscosity and low volatility characteristics, making it unsuitable for diesel engines. Methods: Transesterification of mahua seed oil produces biodiesel with graphite distributed in varying concentrations by ultra sonification. Mahua biodiesel shows reduced viscosity compared to neat vegetable oil, and it will be used as diesel in diesel engines. Graphite nanoparticles contained in mahua biodiesel mix (B30) indicate improved brake thermal efficiency, reduced brake-specific fuel consumption, and reduced carbon monoxide, unburned hydrocarbon, nitrogen oxide, and smoke density. Conclusion: The results of this investigation showed that multi-cylinder diesel engines with direct injection can use optimal blend B30, which incorporates graphite nanoparticles, without requiring any modifications to the engine.

Ultra-low soot/ particulate emissions from a dimethyl ether-fueled agricultural tractor engine

This study eveluates using dimethyl ether (DME) fuelled engine for marching towards zero soot and particulate matter (PM) emissions in the agricultural sector. Comparative emissions and particulate characteristics were analysed for a customised DME-fuelled engine and an unmodified baseline diesel engine. The experimental investigations were performed on a multi-cylinder tractor engine using a dedicated DME fuel injection equipment (FIE) and an unmodified diesel FIE. Regulated emissions, namely carbon monoxide (CO), hydrocarbons (HC), and oxides of nitrogen (NOx), smoke opacity, and particulates were measured at three engine speeds (1200, 1600 and 2000 rpm) and five loads (1.29, 2.59, 3.88, 5.18, and 6.47 bar BMEP). The static fuel injection timing for both test fuels was maintained constant; however, the actual injection timing could be slightly different for both test fuels because of their different physicochemical properties. DME-fuelled engine exhibited relatively higher HC and CO emissions than diesel at low loads; however, both test fuels exhibited nearly identical emissions at higher loads. NOx emissions were lower for DME-fuelled engine than baseline diesel, and its smoke opacity was also negligible at all engine loads and speeds. The particulate number concentration for DME-fuelled engines was much lower than baseline diesel at all test conditions, except 1.29 bar BMEP. Particulate emissions from DME-fuelled engine were mainly in the form of nanoparticles and nucleation mode particles, with negligible numbers of accumulation mode particles. This experimental study demonstrated that DME-fuelling of the tractor engine reduced emissions and it can be used as a sustainable and greener fuel to develop cleaner engines for agriculture/ transport sectors.

Design Optimization of an Ethanol Heavy-Duty Engine Using Design of Experiments and Bayesian Optimization

Abstract Diesel-fueled engines still hold a large market share in the medium and heavy-duty transportation sector. However, the increase in fossil fuel prices and the strict emission regulations are leading engine manufacturers to seek cleaner alternatives without a compromise in performance. Alcohol-based fuels, such as ethanol, offer a promising alternative to diesel fuel in meeting regulatory demands. Ethanol provides cleaner combustion and lower levels of soot due to its chemical properties, in particular its lower level of carbon content. In addition, the stoichiometric operating conditions of alcohol fueled engines enable the mitigation of NOx emissions in aftertreatment stage. With the promise of retrofitting diesel engines to run on ethanol to reduce emissions, the thermal efficiency of these engines remains the primary optimization target. In order to find the optimal ethanol-fueled engine design that maximizes the thermal efficiency, a large design space needs to be investigated using engineering tools. In this study, previous research by the authors on optimizing the design of a single-cylinder ethanol-fueled engine was extended to explore the design space for a heavy-duty multicylinder engine configuration. A heavy-duty engine setup with multiple operating conditions at different engine speeds and loads was considered. A design optimization analysis was performed to identify the potential designs that maximize the indicated thermal efficiency in an ethanol-fueled compression ignition engine. First, a computational fluid dynamics (CFD) model of the engine was validated using experimental data for four drive cycle points. Using a design of experiments (DoE) approach and a parameterized piston bowl geometry, the model was then exercised to explore the relationship among geometric features of the piston bowl and spray targeting angle and indicated thermal efficiency across all tested operating conditions. After evaluating 165 candidate designs, a piston bowl geometry was identified that yielded an increase between 1.3% and 2.2% points in indicated thermal efficiency for all tested conditions, while satisfying the operational design constraints for peak pressure and maximum pressure rise rate. The increased performance was attributed to enhance mixing that led to the formation of a more homogeneous distribution of in-cylinder temperature and equivalence ratio, higher combustion temperatures, and shorter combustion duration. Finally, a Bayesian optimization (BOpt) analysis was employed to find the optimal piston bowl geometry with a fixed spray injector angle for one of the operating conditions. Using BOpt, a piston candidate was identified that resulted in a 1.9% point increase in thermal efficiency from the baseline design, yet only required 65% of the design samples investigated using the DoE approach.

Exploring dilution potential for full load operation of medium duty hydrogen engine for the transport sector

The current political scenario and the concerns for global warming have pushed very harsh regulations on conventional propulsion systems based on the use of fossil fuels. New technologies are being promoted, but their current technological status needs further research and development for them to become a competitive substitute for the ever-present internal combustion engine. Hydrogen-fueled internal combustion engines have demonstrated the potential of being a fast way to reach full decarbonization of the transport sector, but they still have to face some limitations in terms of the operating range of the engine. For this reason, the present work evaluates the potential of reaching full load operation on a conventional diesel engine, assuming the minimum modifications required to make it work under H2 combustion. This study shows the methodology through which the combustion model was developed and then used to evaluate a multi-cylinder engine representative of the medium to high duty transport sector. The evaluation included different strategies of dilution to control the combustion performance, and the results show that the utilization of EGR brings different benefits to engine operation in terms of efficiency improvement and emissions reduction. Nonetheless, the requisites defined for the needed turbocharging system are harsher than expected and result in a potential non-conventional technical solution.

The effect of intake port shape on in-cylinder flow field and turbulence distribution in a high-tumble production engine with endoscope accesses

Three cylinder heads with varied intake port shapes are experimentally investigated to evaluate intake flow structures and their influence on near top dead centre (TDC) flow fields and turbulence distributions in a motored high-tumble engine. The endoscopic high-speed particle image velocimetry (eHS-PIV) is implemented in multi-cylinder engines with two laser endoscopes and a camera endoscope installed in the cylinder head. For a range of engine load and speed conditions, particle seeded and laser illuminated high-speed movies are recorded for 100 cycles with which ensemble-averaged flow fields and spatial-filtered high-frequency flow magnitude distributions are analysed. The results show that a straighter intake port producing a more lateral flow direction results in a larger swinging arc, which is related to enhanced flow later in the compression stroke. The tumble vortex shows an asymmetric structure; the flow field during the compression stroke exhibits higher magnitude vectors at the leading head. This surging flow head becomes stronger with a straighter intake port, which leads to enhanced tumble vortex formation near TDC. As it becomes very strong, the flow vectors originally directed towards the exhaust valves bounce back towards the intake valves, causing a very complex flow structure involving multiple flow components. The result is enhanced turbulence throughout the late compression stroke including the spark timing. However, the impact of the straighter intake port shape on TDC turbulence becomes less significant at lower engine load and speed conditions as the lower intake air momentum limits the enhancement.

Parametric evaluation of neat methanol combustion in a light-duty compression ignition engine

Methanol is currently considered a promising alternative fuel for energy de-fossilization due to its simplicity and adequacy for renewable production. This study investigates the feasibility of using neat methanol in high-efficiency compression ignition engines, with a focus on its potential to reduce CO2 emissions compared to conventional diesel. However, achieving efficient combustion of neat methanol in compression ignition engines presents challenges due to its low ignition capability, requiring higher compression ratios, intake temperatures, and pressures than diesel for autoignition. Furthermore, the high latent heat of vaporization contributes to significant cycle-to-cycle combustion variability. This work evaluates the combustion characteristics of neat methanol in a light-duty multi-cylinder compression ignition engine with a 19:1 compression ratio, examining its suitability for commercial applications. Performance indicators such as engine efficiency, fuel consumption, and engine-out pollutant emissions are assessed. The findings contribute to advancing research and implementation of methanol fuel as an energy source for internal combustion engine vehicles, addressing both the advantages of the fuel and the challenges that need to be overcome, particularly with respect to its low auto-ignition characteristics. Notably, despite methanol's lower energy density compared to diesel, the achieved combustion efficiency is comparable, with remarkable improvements in NOx and soot emissions trade-off.The study reveals that neat methanol combustion poses difficulties, especially at low loads, speeds, and during engine startup, due to its high ignition energy requirement and long ignition delay. Even with modifications such as increased compression ratio, and the addition of intake heaters and glow plugs, sustaining combustion at low load conditions remains a challenge. However, once the engine is warmed up, methanol combustion can be sustained at medium to high loads without additional heating accessories, although the use of such accessories improves combustion stability.

Execution and emission characteristics of automotive compression ignition engine powered by cerium oxide nanoparticles doped water diesel emulsion fuel

The rising consumption of oil and air pollution in developing countries compelled us to seek suitable alternative fuels for the existing compression ignition engines used in power generation, transportation, and industrial sectors, all of which play a strong role in the development of the nation's economy. Moreover, rising demand and consumption also causes a huge impact on our economy as we are dependent on other nations to cater to our needs as domestic production fails to fulfill the present requirement and leads to huge import bills that affect the ordinary man. A water/diesel (W/D) emulsified formulation helps to diminish the engine exhaust discharge without compromising the engine’s performance. The current task experimentally evaluates the execution and discharge characteristics of cerium oxide nano-particles doped water diesel emulsion fuel viz E15, E15CeO2(40), E15CeO2(60), and E15CeO2(80) on multi-cylinder automotive compression ignition engine at steady 1650 rpm, under variable test load situation. Mechanical stirring was used to make E15 water diesel emulsion fuel, whereas ultrasonicator and mechanical stirrer were used to make E15CeO2(40), E15CeO2(60), and E15CeO2(80) blends. Surfactants span 80 and tween 80 were used. The concentrations of cerium oxide nanoparticles in emulsion fuel samples were 40, 60, and 80 ppm, respectively. The characteristics like thickness, flash point, and heating value of test fuels were evaluated and reported within the range as specified by governing standards. The execution and discharge characteristics of various emulsion fuel samples were compared to standard diesel. At maximum load, cerium oxide doped fuels greatly improve engine performance while lowering environmentally harmful engine pollutants such smoke opacity, NOx, carbon monoxide, and hydrocarbon emissions by 40.27%, 33.60%, 30%, and 18.75%, respectively.

Instantaneous Angular Speed-Based Fault Diagnosis of Multicylinder Marine Diesel Engine Using Intrinsic Multiscale Dispersion Entropy

Due to coupling of multiple cylinders during operation and association of high environmental noise, the existing waveform analysis is inefficient to identify the working status of large multi-cylinder marine diesel engines (MCMDE). In order to solve this problem, a new framework named intrinsic multiscale dispersion entropy (IMDE) is proposed by calculating the multiscale dispersion entropy (MDE) of intrinsically reconstructed instantaneous angular speed (IAS) signal. Firstly, intrinsic characteristic scale decomposition (ICD) has been utilized to decompose an IAS signal into principal components. Then, appropriate components are selected for reconstruction of the intrinsically denoised IAS signal. Lastly, working state of the MCMDE is identified by quantifying the intrinsically reconstructed IAS signal with the help of multiscale dispersion entropy (MDE) leading to concept of IMDE. Simulation model corresponding to a v-16 cylinder engine and experimental data collected from a real life v-16-cylinder marine diesel engine are utilized for validation. Results show that the proposed IMDE can extract the effective fault features under different working conditions and has the highest classification accuracy in compare to other existing techniques: MDE, MSE and MFE.

Hydrogen production in ammonia-fueled spark ignition engines

Anhydrous ammonia (NH3) is a promising carbon-free fuel for internal combustion engines (ICEs) that can be generated from renewable energy sources and stored at high energy density. Ammonia is typically mixed with a small fraction of hydrogen (H2), which serves as combustion promoter to achieve stable combustion over a large range of engine operation. To overcome the difficulties of storing hydrogen, ammonia can be converted to hydrogen onboard by means of a catalytic reactor fed by waste thermal energy from the engine exhaust or by partial oxidation. This work explores an alternative method of producing hydrogen by partial oxidation of fuel-rich ammonia–air mixtures to hydrogen in an engine cylinder while generating useful work. Such an approach eliminates the need for costly catalyst materials and poses the possibility of a dedicated reforming cylinder to provide hydrogen for other cylinders in a multi-cylinder engine. Experiments were conducted in a single-cylinder spark-ignition (SI) engine with parametric sweeps of intake temperature, intake pressure, equivalence ratio, and spark timing. Experimental results show that 6% exhaust gas hydrogen concentration is attainable and 40% of the unburned fuel energy can take the form of hydrogen. Rich equivalence ratios produced higher concentrations of hydrogen and elevated intake temperatures extended the rich stable-operation limit of the engine. Low order chemical modeling yields insights into hydrogen production throughout the engine cycle, revealing that initial consumption of ammonia is advanced of hydrogen production and that competing elementary reactions for the formation and destruction of hydrogen drive its net quantity in the exhaust.

Experimental Underperformance Detection of a Fixed-Speed Diesel–Electric Generator Based on Exhaust Gas Emissions

Low load is one of the most challenging combustion stages for a fixed-speed diesel electric generator. Due to incomplete combustion during this phase, a significant proportion of contaminants form inside the cylinder. This can lead to numerous chemical and mechanical harms to the diesel engine, resulting in friction, efficiency reduction, increased fuel consumption, and prematurely ending the generator’s life. These phenomena are qualified as underperformance, possibly due to a misfire and/or a low-efficiency value (air fuel–fuel ratio). Therefore, detecting and preventing underperformance and reducing its extended operation is crucial. This paper deals with the performance and emission analysis of a multicylinder fixed-speed diesel engine driving an electric generator (300 kW) fueled with ultra-low sulfur diesel (≤15 mg/kg) to provide energy in an isolated Canadian community. The tests were carried out according to ISO 3046-1:2002 standard in a remote site to identify clues that can prevent prolonged operation in underperformance. Among the tests conducted, emissions such as sulfur (S), carbon dioxide (CO2), nitrogen oxide (NOx), and exhaust gas temperature are considered the best indices for detecting the underperformance of a fixed-speed diesel–electric generator under very-low and low load (0–30%) with the following registered values: 18 ppm for S, 4% for CO2, 150 ppm for NOx, and 210 °C for the temperature.

The Non-Uniformity Control Strategy of a Marine High-Speed Diesel Engine Based on Each Cylinder’s Exhaust Temperature

To improve the non-uniformity of a multi-cylinder marine diesel engine caused by manufacturing assembly errors and performance degradation of the fuel injection system, with the instantaneous speed applied as the control target, the feedback variable of each cylinder’s exhaust temperature was used to obtain the non-uniformity information and the injection quantity of each cylinder was applied as the control variable; the inhomogeneity control was accomplished by modifying the injection pulse spectrum. The model of AVL Cruise M was established and validated by bench test data. The non-uniformity control strategy based on the instantaneous speed and the exhaust temperature of each cylinder was developed in SIMULINK, and the control effect was compared with the closed-loop control of cylinder pressure by software in-loop simulation. The results showed that the non-uniformity control strategy based on exhaust temperature could significantly improve the uniformity of each cylinder; although the improvement effect was not as great as the non-uniformity control strategy based on cylinder pressure, the cost was significantly reduced, and the practicality and reliability were better. With the closed-loop control of exhaust temperature and instantaneous speed, the CV (Coefficient of Variation) of IMEP (indicated effective pressure) was close to the closed-loop control of cylinder pressure; the maximum occurred at 25% load when it was 0.199%. This co-simulation provided a theoretical basis for the subsequent hardware-in-the-loop simulation and actual engine tests.

Experimental investigation into the effects of Argemone biodiesel/diesel blends on cyclic variations in a multi-cylinder CRDI engine

Abstract Internal combustion engines suffer from high cyclic variations that result in higher emissions, lower efficiency, higher fuel consumption and poor drivability. The purpose of this study is to investigate how Argemone mexicana biodiesel (AGB)/diesel blended fuels affect the cyclic variability of combustion parameters such as maximum cylinder pressure (Pmax) and indicated mean effective pressure (IMEP) in a four-cylinder turbocharged intercooled common-rail direct injection engine under various engine loading conditions. The chemical and physical properties of AGB produced from A. mexicana oil were measured and compared according to the ASTM D6751 standards. In various volumetric ratios, AGB and diesel fuel were blended as D100, AB10 (10% AGB + 90% D100), AB20 (20% AGB + 80% D100) and AB30 (30% AGB + 70% D100). The IMEP and Pmax time-series data were collected over 200 consecutive cycles at low, partial and high engine loads at a constant engine speed of 2000 rpm. The coefficients of variation (COV) of combustion parameters (Pmax and IMEP) were measured for different AGB/diesel blends and found to be within acceptable limits. The results show that COVPmax and COVIMEP decrease as the engine load increases. It was observed that at low load, AB10 has the lowest COV (Pmax, IMEP), and at partial and high load, AB20 has the lowest COV (Pmax, IMEP) among all the blends.

CFD simulation of in cylinder combustion of multi-cylinder diesel engine

The simulation /reproduction of in cylinder combustion for power stroke of multicylinder Diesel Engine is appropriate/fundamental to work upon for determination of temperature inside the cylinder. The current examination incorporates estimating of approximate temperature of in chamber gases during power stroke and accordingly liner temperature from gas side. The current investigation incorporates mathematical simulations dependent on Inbuilt ICE Combustion model in ANSYS 15.0 form, where burning space above cylinder during power stroke which is time transient is utilized. Correct averaged boundary limits were determined for different sections for the ignition model. The mesh modular is created. The prevailing of different ranges of temperature recorded in literature during power stroke along with differential liner temperatures from gas side are surveyed. Estimations are done for maximum and minimum temperatures also. The maximum in cylinder temperature was around 2150 K and least temperature was discovered to be 800 K. Likewise the most extreme temperature on liner from gas side along stroke was discovered to be 470 K during power stroke. It has been additionally discovered that the greatest temperature of in chamber gases and liner from gas side endures just during early power stroke.

One-dimensional numerical investigation on multi-cylinder gasoline engine fueled by micro-emulsions, CNG, and hydrogen in dual fuel mode

This research work is the novel state-of-the-art technology performed on multi-cylinder SI engine fueled compressed natural gas, emulsified fuel, and hydrogen as dual fuel. This work predicts the overall features of performance, combustion, and exhaust emissions of individual fuels based on AVL Boost simulation technology. Three types of alternative fuels have been compared and analyzed. The results show that hydrogen produces 20% more brake power than CNG and 25% more power than micro-emulsion fuel at 1500 r/min, which further increases the brake power of hydrogen, CNG, and micro-emulsions in the range of 25%, 20%, and 15% at higher engine speeds of 2500–4000 r/min, respectively. In addition, the brake-specific fuel consumption is the lowest for 100% hydrogen, followed by CNG 100% and then micro-emulsions at 1500 r/min. At 2500–5000 r/min, there is a significant drop in brake-specific fuel consumption due to a lean mixture at higher engine speeds. The CO, HC, and NOx emissions significantly improve for hydrogen, CNG, and micro-emulsion fuel. Hydrogen fuel shows zero CO and HC emissions and is the main objective of this research to produce 0% carbon-based emissions with a slight increase in NOx emissions, and CNG shows 30% lower CO emissions than micro-emulsions and 21.5% less hydrocarbon emissions than micro-emulsion fuel at stoichiometric air/fuel ratio.

A Neo Emission Reduction Approach for Minimizing Atmospheric Air Pollutants Using Ternary Fuel with Pentanol and Seaweed Anti-Oxidant in Multi-Cylinder Diesel Engine

<p>This research examines the scope for reducing the air pollution caused by the transportation sector through the infusion of biofuel and antioxidants ensuring the partial replacement of conventional fuel. A four-stroke, direct-injection, multi-cylinder and constant-speed diesel engine was employed for the experimental analysis. The ternary fuel blend with a composition of 70% diesel fuel, 20% rubber seed oil and 10% of pentanol and sea weed extract in different ratios were blended to form B20, B20A1, B20A2 and B20A3. The experimental results showed smoke and carbon monoxide reduced by 4.71%, unburned hydrocarbons by 2.2 %. The NOx emission which was slightly higher compared to diesel but not higher than B20 for the blend B20A2 by 5%. The brake thermal efficiency was increased by 3.71% when compared to diesel fuel. Consequently, the B20A2 (5% seaweed and 5% pentanol additive with 70% diesel and 20% of rubber seed methyl ester oil) was found to be an environmentally biodegradable gasoline with the best emission properties. The study findings are quite promising for future which seeks towards zero emission with optimum quantity of biofuel to replace diesel.</p>

Study of aircraft radial piston engines noise

The results of the study of acoustic characteristics of aircraft radial piston engines ASH-62IR and M-14P are presented. The tests were carried out during the race of the power plants of the AN-2 and Yak-18T light propeller-driven aircrafts under static conditions at the local aerodrome. It is shown that the method of organizing the exhaust of a multi-cylinder engine determines the main tone frequency. The influence of the engine power condition on the directivity of the tonal noise components is considered. The dependences of the sound power on the engine speed are obtained.

Numerical Analysis of Two-Stage Turbine System for Multicylinder Engine under Pulse Flow Conditions with High Pressure-Ratio Turbine Rotor

Internal combustion engine (ICE) exhaust gases provide a high amount of energy which is partially lost to the environment. Such energy can be recovered with a turbocharger turbine or other after-treatment device. As the engine exhaust flow varies not only with the engine load but also with the opening and closing of the exhaust valves, a proper matching between the engine and the turbine should be established to maximize the recovery of waste energy. That is why a twin-scroll or dual turbocharging system is implemented, especially in multi-cylinder engines. Such systems require a very complex pipeline to eliminate the interference of the exhaust pulses between the adjacent cylinder ignitions. In this study, the two-stage, multi-channel turbine system was investigated for two different rotor geometries: the old, high-performance rotor A and the smaller but more modern rotor B, which was scaled to match rotor A. Both geometries were compared at three different turbine speeds and variable turbine geometry (VTG) vane positions. It was found that the two-stage turbine system with rotor B geometry provided an 8% higher total efficiency than rotor A due to the lower flow losses within the rotor passage.

Theoretical calculations of the relative additional fuel consumed when shutting down the cylinder

Cylinder deactivation is a technique used to improve the efficiency of an engine by shutting down a certain number of engine cylinders. Cylinder deactivation allows the remaining cylinders to operate more efficiently, increasing their load and improving efficiency. This technique has gained interest both domestically and internationally, particularly for automotive engines, as it helps improve fuel economy at idle and light loads. The process of calculating effective cylinder deactivation in a multi-cylinder engine and its effect on additional fuel consumption is discussed. The need to improve engine efficiency in various speed and load modes is driven by requirements for fuel economy, reduced exhaust toxicity, and the need to improve engine transients while maintaining other characteristics. In order to effectively utilize engine power and maintain performance, the fuel supply to operating cylinders must be increased. However, deactivating cylinders during engine operation results in a decrease in engine power, which in turn reduces crankshaft speed and torque. In summary, cylinder deactivation is a technique that has the potential to improve the economic performance of engines, particularly at idle and light loads. A method for effectively deactivating cylinders in multi-cylinder engines has been developed based on the dependence of indicator efficiency on load changes. The study examined the effect of cylinder deactivation on mechanical losses and efficiency when load is reduced from 100% to 30%. The results showed that it is possible to use only two cylinders of a four-cylinder engine at 30% load, resulting in reduced mechanical losses and improved efficiency. A proposed method for determining the relative additional fuel consumption when cylinders are deactivated is presented. Deactivated cylinders do not supply air to the exhaust manifold, which reduces pumping losses and creates less rolling resistance, resulting in up to a 25% reduction in fuel consumption. This reduction is especially noticeable in urban driving.

Comparative study on multi-cylinder DI diesel engine using hybrid fuel blends (diesel-biodiesel-ethanol derivative) as fuel

Comparative study on multi-cylinder DI diesel engine using hybrid fuel blends (diesel-biodiesel-ethanol derivative) as fuel

Throttling Effect on the Performance and Emissions of a Multi-Cylinder Gasoline Fuelled Spark Ignition Engine

The throttle mechanism, a regulatory technique of engine output, is accompanied by a loss of some energy. The effect of intake air throttling on the performance and emissions of a multi-cylinder spark ignition gasoline engine was experimentally investigated. The engine was coupled to a hydraulic dynamometer equipped with a customized cooling system for both the engine and dynamometer. Experimental tests were performed for various engine speeds and air-fuel ratios at the WOT and POT conditions with optimized ignition timing. The acquired results recorded that a better engine operation could be achieved with WOT in terms of bmep, bsfc, ηb, CO, CO2 and UHC compared to POT. At the same time, the worst trend at WOT was noticed for the NOx concentration due to the higher conversion efficiency of fuel combustion. In terms of engine speed for both WOT and POT conditions, operating at 3000 rpm represents the minima of ϕ, bsfc, CO and UHC; and the maxima of ηb, CO2 and NOx with some fluctuation on both sides of this point. Maximum recorded values of ηb were about 30.55% and 28. 55%, while the minimum values of bsfc were about 274 and 293 g/kW.h for the WOT and POT conditions, respectively. The maximum bmep was obtained at 2500 rpm at WOT and POT conditions with values of about 940 kPa and 904 kPa, respectively. Maximum recorded values of NOx were about 1525 and 977 ppm for the WOT and POT conditions, respectively.