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Future engine control systems need suitable and accurate models for combustion. For this purpose, this paper presents a practical application of nonlinear autoregressive moving average polynomial models with exogenous inputs (NARMAX) technique to model pressure dynamics inside the cylinder of a direct injection compression ignition engine. Two models have been investigated taking two different sets of input variables. The first model only includes basic injection settings available from the electronic control unit. The second model uses the instantaneous crankshaft revolution speed as a main model input. Model parameter identification and validation are performed with experimental data obtained from a test engine equipped with a piezoelectric pressure sensor and with data computed from a thermodynamic-based engine cycle simulation code.

To provide fuel/air ratio quantitative measurements in an S.I engines, a transparent cylinder engine is investigated with the Fuel-Air Ratio Laser Induced Fluorescence (FARLIF) technique. In a homogeneous mixture, the two dimensional distribution for the fuel/air ratio is calibrated and measured during the compression stroke for different equivalence ratios. After spark ignition, the combustion zone and the flame front are visualized by laser sheet LIF. The direct-injection stratified-charge, new concept for gasoline engines is investigated with FARLIF. In the direct injection gasoline engine where the fuel is directly injected into a cylinder and the flow is highly turbulent, two injection timings are used: -early injection (i.e. during the intake stroke) to promote a homogeneous distribution; -late injection during the compression stroke, to generate a ultra-lean stratified charge.