NANO

ENGINE 5 A Fuel Selector Switch is provided on the dashboard to select the fuel desired by the driver Starting: Winter: The engine starts in petrol mode irrespective of the fuel mode selected when the engine /coolant temperature is 10deg C and below which typically occurs during the winter season. The engine converts to CNG mode automatically when the engine warms up. Once warmed up, the engine starts and runs in CNG, if CNG mode is selected Other seasons: The engine starts and runs in CNG, if CNG mode is selected Starting time in CNG will be longer than in petrol (approx 1 sec longer than petrol starting time) due to the physical characteristics of the fuel. To start, turn the ignition “ON”, press the clutch pedal fully and crank. Do not press the accelerator pedal. Important: Your car will run automatically in petrol mode for almost 2 to 3 km after every 60-70 Kms covered in CNG mode to keep the petrol system & CNG system in good condition . Idle Air Control: Proper Idling of the engine is ensured irrespective of the fuel modes - CNG or Petrol - under different operating conditions with the help of closed loop control. The ECU controls the IACV to ensure stable idling. Engine Load Determination: CNG Fuelling and Ignition timing requirements of the engine are dependent on the Engine load. The Load determination is done using the 'Model Based Fuelling' (MBF) strategy. The strategy uses the estimated temperature and pressure at the intake port together with the engine speed to estimate the amount of air entering the cylinder at the next induction stroke. To calculate the airflow as precisely as possible, a thermal model of the Intake manifold is used, which is a correction factor applied to the load equation to determine the correct amount of the fuel to deliver to the engine. This model also serves as a backup strategy if either the Throttle Position or Manifold Absolute Pressure Sensors fails. The manifold also takes into account of all temperature variations (E.g.: purging) that will occur during the running. Fuelling (CNG): The CNG in the form of a ‘gas’ is injected into the Inlet ports by the Gas Injectors. These injectors are controlled by the ECU for the precise injection quantities and timings. The amount of the fuel delivered during each engine cycle is proportional to duration of the Injector open time. Injector timing (phasing) is controlled to optimise performance. The injection is sequential i.e. each injector is opened relative to its own cylinder timing. Amount of the ‘fuel’ required (i.e. the Injector pulse time) depends largely on the engine load and speed. Further adjustments are to account for the variations in the operating conditions (CNG temperature & CNG pressure). A closed loop fuelling system is used – a further correction is applied to the open loop pulse time to maintain a stoichiometric air fuel ratio. The closed loop system also provides adaptive (‘Learning’) fuelling to compensate for the component tolerances and aging. The deceleration fuel cut-off is provided for fuel economy and improved emission performance. Ignition: The Ignition is controlled electronically by the ECU. The optimum ignition timing is maintained depending upon the engine speed and load. Further small corrections are applied to improve drivability and to account for the variations in the operating conditions (e.g. engine temperature, Inlet air temperature). The ignition timing is also adjusted in conjunction with the Idle Air Control Valve to control the idle speed of the Engine. In order to provide the best torque in both petrol and CNG modes, the ECU has dedicated ignition timing maps for check fuel mode which is mapped to provide optimum torque without knocking. Throttle Position and Adaptation: The throttle position potentiometer output may differ between vehicles and can also change overtime due to component aging. A corrective term is applied to compensate for this effect; this is an adaptive (‘learning’) value that’s updated throughout the vehicle’s life