Combustion In Spark Ignition Engine Research Articles

Effects of pressure rise rate on laminar flame speed under normal and engine-relevant conditions

Laminar flame speed (LFS) is one of the most important physicochemical properties of a combustible mixture. At normal and elevated temperatures and pressures, LFS can be measured using propagating spherical flames in a closed chamber. LFS is also used in certain turbulent premixed flame modelling for combustion in spark ignition engines. Inside the closed chamber or engine, transient pressure rise occurs during the premixed flame propagation. The effects of pressure rise rate (PRR) on LFS are examined numerically in this study. One-dimensional simulations are conducted for spherical flame propagation in a closed chamber. Detailed chemistry and transport are considered. Different values of PRR at the same temperature and pressure are achieved through changing the spherical chamber size. It is found that the effect of PRR on LFS is negligible under the normal and engine-relevant conditions considered in this study. This observation is then explained through the comparison between the unsteady and convection terms in the energy equation for a premixed flame.

Quasi-Dimensional Multi-Zone Combustion Diagnostic Tool for SI Engines with Novel NOx and CO Emissions Models

<div class="section abstract"><div class="htmlview paragraph">In this work a quasi-dimensional multi-zone combustion diagnostic tool for homogeneous charge Spark Ignition (SI) engines is analytically developed for the evaluation of heat release, flame propagation, combustion velocities as well as engine-out NOx and CO emissions, based on in-cylinder pressure data analysis. The tool can be used to assess the effects of fuel, design and operating parameters on the SI engine combustion and NOx and CO emissions formation processes.</div><div class="htmlview paragraph">Certain novel features are included in the presently developed combustion diagnostic tool. Firstly, combustion chambers of any shape and spark plug position can be considered due to an advanced model for the calculation of the geometric interaction between a spherically expanding flame and a general combustion chamber geometry. Also, the temperature stratification of the burned gas developed during the combustion phase, which has to be captured for the theoretically realistic estimation of the in-cylinder formation of pollutant emissions, is taken into account by a multi-zone thermodynamic treatment. According to this, multiple spherically allocated burned zones are sequentially generated at specified (user-defined) crank angle intervals, forming overlapping shells. Moreover, complex chemical equilibrium compositions are computed, which can include any user-defined mixture of species in the combustion products, using an advanced modular method based on the minimization of Gibbs energy. Furthermore, NOx and CO engine-out emissions are calculated based on novel in-cylinder formation models presented by the authors in the past. Specifically, NOx emissions are evaluated by a global algebraic NOx emissions formation model, accounting for both thermal and N<sub>2</sub>O pathway NO formation, based on the calculation of the characteristic timescales of the relevant NO formation mechanisms. CO emissions are assessed using a new kinetics-based model, consisting of a single Ordinary Differential Equation (ODE) that can be analytically integrated. The CO emissions model is derived considering the dynamics of a representative pool of active radicals in post-flame gases and explicitly describes the CO oxidation quenching process.</div><div class="htmlview paragraph">The combustion diagnostic tool is applied to a lean burn gas engine at various engine speeds under full load conditions and constant lambda value. Various combustion and NOx and CO emissions related results are presented and discussed to illustrate the capabilities of the tool for combustion diagnosis, while at the same time calculated engine-out NOx and CO emissions are found to be in satisfactory agreement with measured ones.</div></div>

Thermal efficiency improvement of super-lean burn spark ignition engine by stratified water insulation on piston top surface

In order to improve thermal efficiency of spark ignition engine under super-lean burn conditions (excess air ratio [Formula: see text]), thermal stratification technique by in-cylinder water injection toward piston surface (stratified water insulated combustion architecture), in which low temperature water vapor layer is formed on the surface, is proposed. From the water spray visualization using the optically accessible engine, injected water is distributed near the piston top surface at ignition timing and thermal stratification can be achieved in the case that water injection timing (SOIw) is set at earlier stage of a compression stroke. In addition, heat flux on the piston surface measured at the same time is reduced by water injection. The 0.5-L single-cylinder engine test at λ = 2.0 at a constant ignition timing also shows that water injection at earlier stage of a compression stroke makes it possible to mitigate knock without significant increase in combustion instability. On the other hand, part of water is distributed near the spark plug at ignition timing with the water injection at SOIw = −60 °ATDC, resulting in unstable combustion. In addition, the engine test at λ = 2.0 and water/fuel ratio(W/F) = 18% shows that knock mitigation by water injection enables spark advance and following combustion enhancement. As a result, combustion period becomes short and cooling loss decreases, followed by the 1.0-pt improvement of gross indicated thermal efficiency. Moreover, the engine can be operated at minimum spark advance for best torque by increasing W/F up to 35%. Finally, stratified water insulated combustion architecture concept is applied at λ = 1.9 with a higher compression ratio of 17, showing that water injection at SOIw = −120 °ATDC and W/F = 50% enables minimum spark advance for best torque operation, and remarkably high gross indicated that thermal efficiency of 52.63% can be achieved with a sufficiently low knock level and coefficient of variation of indicated mean effective pressure.

1D numerical study on hydrogen injection enabling ultra-lean combustion in a small gasoline Spark Ignition engine

This paper deals with the effects of hydrogen port injection on combustion evolution, efficiency and exhaust emissions of a small turbocharged gasoline Spark-Ignition engine through a 1D numerical code. First, the experiments on the base engine architecture are performed at different speeds and at low/medium loads. The experimental findings are used to validate a 1D model of the whole engine, developed within a commercial code. 1D model is also refined with “user-defined” sub-models for an accurate description of the in-cylinder phenomena, namely turbulence, combustion, heat transfer, and emissions. In a second step, 1D model is virtually modified through the installation of an hydrogen injector in each intake runner, while the combustion sub-model also accounts for the impact of hydrogen addition on the laminar flame speed through a dedicated correlation. 1D simulations are performed at low/medium loads and fixed speed of 2250 rpm with 5% of hydrogen by volume in the intake air. Numerical investigations show that hydrogen addition to gasoline/air mixtures allows relevant efficiency benefits (up to a maximum percent gain of 19%), while the NO emissions are almost eliminated. Consequently, hydrogen-boosted combustion represents a potential solution to achieve very high efficiency and reduced pollutant emissions of gasoline spark ignition engines equipped with a conventional combustion system.

Normal-gamma distribution–based stochastic knock probability control scheme for spark-ignition engines

Spark timing, one of the essential parameters to control combustion in spark-ignition gasoline engines, is often advanced to optimize the power output and fuel economy. An overly advanced spark timing, or equivalently a large spark advance, however, can lead to severe knocking under heavy load engine operating conditions. In a trade-off between engine damage avoidance and power enhancement, the knock probability has to be regulated at a low percentage. Based on the observation that the logarithm of the knock intensity under steady operating conditions follows a normal distribution, in this research, a Bayesian knock probability estimation method is proposed using the normal-gamma distribution and the observed knock intensity. Based on the estimation, a spark advance control algorithm is also developed. The proposed knock probability control algorithm is validated on a full-scale test bench with a production spark-ignition engine. The results show that the proposed method is capable of regulating the knock probability to be close to the target percentage. With different parameter settings, the controller can further be configured to behave more aggressively or conservatively in knock probability estimation and regulation. In comparison with the conventional controller and the maximum likelihood–based controller, and in the tip-in/tip-out test, the proposed method also presents a quick response to transient engine operating conditions and a low spark advance dispersion after the spark advance converges close to the borderline.

Numerical investigations on hydrogen-enhanced combustion in ultra-lean gasoline spark-ignition engines

Performance of lean-burn gasoline spark-ignition engines can be enhanced through hydrogen supplementation. Thanks to its physicochemical properties, hydrogen supports the flame propagation and extends the dilution limits with improved combustion stability. These interesting features usually result in decreased emissions and improved efficiencies. This article aims at demonstrating how hydrogen can support the combustion process with a modern combustion system optimized for high dilution resistance and efficiency. To achieve this, chemical kinetics calculations are first performed in order to quantify the impacts of hydrogen addition on the laminar flame speed and on the auto-ignition delay times of air/gasoline mixtures. These data are then implemented in the extended coherent flame model and tabulated kinetics of ignition combustion models in a specifically updated version of the CONVERGE code. Three-dimensional computational fluid dynamics engine calculations are performed at λ = 2 with 3% v/v of hydrogen for two operating points. At low load, numerical investigations show that hydrogen enhances the maximal combustion speed and the flame growth just after the spark which is a critical aspect of combustion with diluted mixtures. The flame front propagation is also more isotropic when supported with hydrogen. At mid load, hydrogen improves the combustion speed and also extends the auto-ignition delay times resulting in a better knocking resistance. A maximal indicated efficiency of 48.5% can thus be reached at λ = 2 thanks to an optimal combustion timing.

A semi-empirical laminar-to-turbulent flame transition model coupled with G equation for early flame kernel development and combustion in spark-ignition engines

It has been reported that early combustion in a spark-ignition engine determines the subsequent combustion. Also, the early combustion has a very strong correlation with cycle-to-cycle variability, which limits engine operating range. As such, accurate modeling of the early flame development is very important in accurate simulation of spark-ignition engine combustion. During the early flame development, the flame kernel, initiated by spark, grows initially at laminar flame speed. As the kernel grows, the flame surface wrinkles due to surface instability and interacts with the flow turbulence as the flame transitions from laminar to turbulent flame. In this study, a semi-empirical model is proposed to simulate the laminar-to-turbulent flame transition process during early spark-ignition combustion. A hyperbolic tangent function was used to emulate the laminar-to-turbulent flame speed transition process. The proposed transition function was evaluated during early flame kernel development for both Reynolds-averaged Navier–Stokes and large eddy simulation models against combustion analysis data from high-speed optical particle image velocimetry. Difference in Reynolds-averaged Navier–Stokes and large eddy simulation transition function was analyzed and discussed.

Combustion variation control strategy with thermal efficiency optimization for lean combustion in spark-ignition engines

A widespread consensus among internal combustion engine researchers is that higher thermal efficiency can be achieved with lean combustion. However, compared with a normal combustion mode (i.e., under a stoichiometric air-fuel ratio), combustion variation under lean operation is much more distinct, creating a bottleneck of thermal efficiency maximization. In this paper, a combustion variation control strategy that considers thermal efficiency optimization is proposed. This proposed strategy consists of two main components. One component focuses on diminishing combustion variation from cylinder to cylinder using a hypothesis test-based method. The other component provides the optimal value by searching for spark timing to maximize thermal efficiency. The effectiveness and performance of the proposed method are experimentally validated on a production spark-ignited gasoline engine test bench. From the experimental results, a notable combustion variation restrain performance with an average of 27% variation reduction is achieved using the proposed method. In addition, the self-optimization performance of spark timing under environmental changes is proven to be effective.

Modeling cycle-to-cycle variations in spark ignited combustion engines by scale-resolving simulations for different engine speeds

Here, internal combustion engine operating speed effects on combustion cycle-to-cycle variations (CCV) are numerically investigated. The recent study by Ghaderi Masouleh et al. (2018) is extended to higher engine speeds including 560, 800 and 1000 RPM. The 3D scale-resolving simulations are carried out in a spark ignited simplified engine geometry under fuel lean condition. The numerical results include the following main findings. (1) Flow velocity and turbulence levels are noted to increase with RPM. (2) For a fixed spark timing, the combustion duration in CAD time increases with RPM contrasting the respective trend in physical time. (3) The link between early flow conditions around the spark position and the whole cycle combustion rate is demonstrated and explained for all the RPM for the investigated three example cycles. (4) On average, the moderate increase of turbulent flame speed with RPM is not able to compensate the reduced physical time for combustion. Hence, the higher RPM cycles burn typically slower in CAD time. (5) On average, the increased combustion duration in CAD time for higher RPM increases the CAD period, where the spark kernel is highly prone to local turbulence fluctuations. (6) A noted effect of RPM on CCV is the stretched combustion duration in CAD time so that the effect of the initial fluctuations can persist for a longer CAD period. (7) In the present model, the velocity magnitude near the spark largely explains cycle-to-cycle variations in the investigated low RPM range.

Effect of swirl at intake manifold on engine performance using ethanol fuel blend

ABSTRACTEthanol fuel is widely used as an alternative fuel in spark ignition engines. The use of ethanol reduces dependence on fuel from the fraction of hydrocarbons. As such, adding swirl generators to the intake manifold aims to make the internal airflow more turbulent. The influence of swirl on the performance, emissions, and combustion in a constant speed Spark Ignition (SI) engine was studied experimentally. Also, the effects of the addition of ethanol in the fuel on engine performance and emissions under development of the intake manifold with a swirl generator were determined. Thus, the study analyses the effects of adding a swirl generator to the intake manifold on engine performance, fuel consumption, and emissions produced. Influence of the swirl generator on the airflow and swirl pattern testing is done on the three types of swirl generators, which are the concave, flat bottom, and symmetrical with different angle positions. Engine experiment was performed at 2,000, 2,500, 3,000, 3,500, 4,000, 4,500, and 5,000 rpm engine speed at WOT using a concave swirl type generator. Response Surface method (RSM) was used to find the optimum intake manifold design according to response (flow and swirl) and independent variables (a type of swirl generators and angle positions). The concave swirl type generator at 6.53 angle position is considered to be optimum for this particular engine. The highest engine torque and BSFC were with a swirl generator intake manifold. The HC and CO emissions increased with intake manifold with a swirl generator. The CO2 emission reduced with swirl generator intake manifold by 2%, 3%, and 5% with gasoline E10 and E20 compared to the standard intake manifold.

Computational Investigation of Porous Media Combustion Technology in Spark Ignition Engine

In the present work, computational fluid dynamics approach is adopted to study the possibility of using porous media in combustion and emission in a single-cylinder four-stroke spark ignition engine. The combustion behavior inside the engine without and with application of porous media is studied. The analysis with application of PM signifies enhanced combustion behavior. The compression ratio is kept at 7. Two different types of fluid computational domains are considered, namely, without and with PM. The three-dimensional modeling, meshing and simulations of the combustion chambers are performed with the ANSYS 17.1-FLUENT software. The k–e turbulence model, the premixed combustion model and the spark ignition model are used in the study. The parameters to be analyzed are the variation of cylinder pressure, temperature and turbulence at different crank angles. The results of the computational work without PM are validated with the experimental work, which is executed on the research engine setup operated in SI mode. The work is performed at different engine loads by varying the engine torque, viz. 6 Nm (25%), 12 Nm (50%), 18 Nm (75%) and 24 Nm (100%) along with the no-load condition. The analyses of the results indicate that the peak value of total pressure (1,986,868.99 Pa) and average value of total temperature (632.63 K) with PM at 100% load are lower than without PM (1,992,314.50 Pa and 604.81 K). The concentrations of NOX emissions are significantly reduced by the use of PM for all the loads. The percentage reductions in NOX emissions at no load, 25%, 50%, 75% and 100%, are found to be 2.5%, 11.1%, 9.4%, 9% and 2.12%, respectively.

A study of hydrous ethanol combustion in an optical central direct injection spark ignition engine

The aim of this experimental work was to improve understanding of the influence of hydrous ethanol on combustion in an engine demonstrating a tendency for biased flame migration towards the hotter exhaust walls as often reported for typical modern pent roof design IC engines. The work aimed to uncover the degree of residual water content that can be reasonably tolerated in terms of combustion characteristics in future ethanol SI engines (with the energy required to reduce water levels then potentially reduced). The experiments were performed in a single cylinder optical research engine equipped with a modern central direct injection combustion chamber and Bowditch type optical piston. Results were obtained under part-load engine operating conditions (selected to represent typical highway cruising conditions) with hydrous ethanol at 5%, 12% and 20% volume water. Baseline results were obtained using pure isooctane. High-speed cross-correlated particle image velocimetry was undertaken at 1500 rpm under motoring conditions with the intake plenum pressure set to 0.5 bar absolute. The horizontal imaging plane was fixed 10 mm below the combustion chamber “fire face”. Comparisons were made to CFD computations of the in-cylinder flow. Complimentary flame images were obtained via the “natural light” (chemiluminescence) technique over multiple engine cycles. The flame images revealed the tendency of an iso-octane fueled flame to migrate towards the exhaust side of the combustion chamber, with no complimentary bulk air motion apparent in this area in the horizontal imaging plane. The faster-burning ethanol offset this tendency of the flame to migrate towards the hotter exhaust walls. The fastest combustion rate occurred with pure ethanol, with higher water content (>5%) generally slowing down the flame speed rate to 10.64 m/s from 10.92 of ethanol and offsetting the flame speed/migration benefit (in good agreement with recent laminar burning velocity correlations for hydrous ethanol). When adding 20% water to ethanol the combustion rate was significantly slower (8.2 m/s) with a considerable increase in flame shape distortion as quantified by flame image shape factor values. The results demonstrate how the added water increases flame distortion and leads to higher flame centre displacement. Such flame centre displacement could potentially be offset in the future with a spark plug location biased further towards the intake side of the chamber (albeit sometimes practically constrained by the priorities given to intake valve sizing and local cooling jacket design). The results indicate that ethanol fuels offset such bias flame growth and allow residual water to be tolerated for an equivalent degree of biased flame migration. The implication is reduced fuel production energy and cost required to produce usable ethanol fuels.

Characterization of radiative heat transfer in a spark-ignition engine through high-speed experiments and simulations

A combined experimental and Large-Eddy Simulation (LES) study of molecular radiation is presented for combustion in a homogeneous pre-mixed spark-ignition engine. Molecular radiation can account for ~10% of the engine heat loss and could have a noticeable impact on the local conditions within the combustion chamber. The Transparent Combustion Chamber (TCC) engine, a single-cylinder two-valve research engine with a transparent liner and piston for optical access, was used for this study. High-speed infrared emission spectroscopy and radiative post-processing of LES calculations have been performed to gain insight into the timescales and magnitude of radiative emissions of molecular gases during the combustion process. Both the measurements and simulations show significant Cycle-to-Cycle Variations (CCV) of radiative emission. There is agreement in the instantaneous radiative spectrum of experiment and simulation, but the crank-angle development of the radiative spectrum shows disagreement. The strengths and limitations of the optical experiments and radiative simulations are seen in the results and suggest pathways for future efforts in characterizing the influence of molecular radiation. In particular, focusing on the relative changes of the spectral features will be important as they contain information about the thermochemical properties of the gas mixture.

Stereoscopic Particle Image Velocimetry Measurements and Proper Orthogonal Decomposition Analysis of the In-Cylinder Flow of Gasoline Direct Injection Engine

Intake generated flows are known to have a fundamental influence on the combustion both in spark ignition (SI) and compression ignition engines. This study experimentally investigated the tumble flow structures inside a cylinder of gasoline direct injection (GDI) engine utilizing a stereoscopic time-resolved particle image velocimetry (PIV). The experiments were conducted in a GDI engine head for a number of fixed valve lifts and 150 mmH2O pressure difference across the intake valves. A tumble flow analysis was carried out considering different vertical tumble planes. In addition, the proper orthogonal decomposition (POD) identification technique was applied on the PIV data in order to spatially analyze the structures embedded in the instantaneous velocity data sets. The results showed that the flow was dominated by a strong tumble motion in the middle of cylinder at high valve lifts (8–10 mm). Moreover, it is worth pointing out that, because of the complexity of the flow at the high valve lifts, the flow energy was distributed over a higher number of POD modes. This was confirmed by the need of a higher number of POD modes needed to reconstruct the original velocity field to the same level of fidelity.

The influence of mixing ratio of low carbon mixed alcohols on knock combustion of spark ignition engines

Alcohol fuels, owing to the characteristics of oxygen-containing and high octane number, are considered as one potential alternative fuel additive in spark ignition (SI) engines. In this paper, the ethanol and n-butanol are blended with gasoline to form the new low-carbon mixed alcohols-gasoline blended fuels. The effect of different mixing proportions of ethanol and n-butanol in gasoline on knock combustion and fuel economy of SI engine was studied by experiment and simulation. The results showed that with the increase of n-butanol ratio, brake specific fuel consumption (BSFC) increase, but knock index (KI) and knock intensity decrease. Moreover, crank angle delays under the same knocking condition when the engine fueled with E5-Bx and B5-Ey fuel, and the crank angle is delayed more significantly with the increase of engine speed. In addition, when the ethanol and n-butanol are blended as the same proportion in gasoline (i.e. x = y), the KI and knock intensity of E5-Bx fuel is lower than that of B5-Ey, which indicates that the B5-Ey fuel has better antiknock property. But the BSFC of B5-Ey is slightly greater than that of E5-Bx under the same operating condition, that is, the B5-Ey fuel has higher fuel consumption.

Reduced Kinetic Mechanism for Methanol Combustion in Spark-Ignition Engines

A reduced kinetic mechanism for methanol combustion at spark-ignition (SI) engine conditions is presented. The mechanism consists of 18 species and 55 irreversible reactions, small enough to be sui...

Differences between PREMIER combustion in a natural gas spark-ignition engine and knocking with pressure oscillations

PREMIER (PREmixed Mixture Ignition in the End-gas Region) combustion occurs with auto-ignition in the end-gas region when the main combustion flame propagation is nearly finished. Auto-ignition is triggered by the increases in pressure and temperature induced by the main combustion flame. Similarly to engine knocking, heat is released in two stages when engines undergo this type of combustion. This pattern of heat release does not occur during normal combustion. However, engine knocking induces pressure oscillations that cause fatal damage to engines, whereas PREMIER combustion does not. The purpose of this study was to elucidate PREMIER combustion in natural gas spark-ignition engines, and differentiate the causes of knocking and PREMIER combustion. We applied combustion visualization and in-cylinder pressure analysis using a compression–expansion machine (CEM) to investigate the auto-ignition characteristics in the end-gas region of a natural gas spark-ignition engine. We occasionally observed knocking accompanied by pressure oscillations under the spark timings and initial gas conditions used to generate PREMIER combustion. No pressure oscillations were observed during normal and PREMIER combustion. Auto-ignition in the end-gas region was found to induce a secondary increase in pressure before the combustion flame reached the cylinder wall, during both knocking and PREMIER combustion. The auto-ignited flame area spread faster during knocking than during PREMIER combustion. This caused a sudden pressure difference and imbalance between the flame propagation region and the end-gas region, followed by a pressure oscillation.

On autoignition mode under variable thermodynamic state of internal combustion engines

Autoignition modes under premixed combustion conditions are usually studied in constant-volume configurations. However, the autoignition events related to knocking combustion in spark-ignition engines do experience variable volumes in combustion chamber and ever-changing thermodynamic states caused by reciprocating piston motion and main flame front compression. Such combustion situations may lead to different autoignition modes from constant-volume scenarios. Using one-dimensional direct numerical simulations with detailed chemistry and transport of H2/air mixture, the autoignition modes during knocking combustion were studied under different engine combustion boundary conditions. It was the first to identify important influence of variable thermodynamic states on the development of autoignition modes through changing critical temperature gradients. Four autoignition modes—thermal explosion, supersonic deflagration, detonation, and subsonic deflagration—were observed, which, however, were quantitatively different from the constant-volume configurations in regime boundaries. Meanwhile, on comparison with intake temperature and equivalence ratio, intake pressure shows greater impact on detonation formation, characterized by a regime extension under high intake pressures. To classify the autoignition modes responsible for various knocking events with different intensities in a straightforward manner, a regime diagram was proposed based on the temperature gradients and the effective energy density used for universally quantifying various intake conditions. This diagram was found useful to determine the distributions of different autoignition modes (especially for detonation) and the potential approaches for achieving maximum thermal efficiency while suppressing engine knock. In addition, detonation mode was prevailing under high effective energy density conditions, and the underlying reasons were ascribed to the significant reduction of excitation time and pre-flame temperature increases by pressure wave.

Comparative studies of harmful exhaust emission from a hybrid vehicle and a vehicle powered by spark ignition engine

To better reflect real-world emissions of harmful exhaust, substances from light-duty vehicles, the WLTP cycle (World Light Test Procedure) was introduced in laboratory tests. This article discusses that test and conditions for its implementation in the context hitherto in force of the NEDC cycle (New European Driving Cycle). The article presents results of emission tests of two vehicles: one hybrid (electric motor + spark ignition combustion engine) and the other with an internal combustion engine with similar rated powers in the above-mentioned WLTP cycle. Reference is made mainly to the gaseous pollutant road emissions, i.e.: CO, CO2, THC, NOX. A comparison of the above emission with the one obtained for both vehicles in the NEDC cycle was also made.

Operational feasibility of a spark ignition engine which is subjected to VTEC management strategy

ABSTRACT A validated spark ignition engine combustion model was used to investigate the operational feasibility of subjecting a 5.734 l, V8 engine to the Honda variable (valve) timing and electronic lift control (VTEC) management strategy. The numerical results were found to be in good agreement with measured data during the compression and expansion strokes. However, the results of the numerical model overestimated the measured data by approximately 10%–15% during the combustion phase. The reason for this discrepancy could be due to the fact that the turbulence levels within the combustion chamber during the experiment was not specified. Therefore, we accounted for turbulence in the simulation with a flame speed multiplying factor, . The investigations cover operations at low, mid-range and full power periods; for fuel-air equivalence ratios, of . The results of the study show that operational viability of a 5.734 l, V8 engine when subjected to the VTEC engine management scheme was achievable, provided high levels of turbulence were maintained, especially for extra lean mixtures, that is, for fuel-air equivalence ratio, . This work shows that the values of the flame speed factor, have to be carefully selected in order to achieve complete combustion.