Controles eletrônicos do motor – Funcionamento do sistema e componentes

Electronic Engine Controls – 2.5L Duratec-HE (122kW/165PS) 303-14A-6 303-14A-6 - MI4 DESCRIPTION AND OPERATION primary circuit, thereby producing an ignition spark which passes to the cylinder via the spark plug. The spark plugs are activated in pairs (cylinders 1 and 4, and cylinders 2 and 3) and send a strong main spark to the cylinder in the compression cycle and a weak secondary spark to the cylinder in the exhaust cycle. The main spark is generated automatically in the cylinder that is in the compression cycle, because a higher resistance exists between the electrodes on account of the high compression. On one spark plug a spark jumps across from the center electrode to the earth electrode and on the other spark plug from the earth electrode to the center electrode. Crankshaft Position (CKP) Sensor E135521 The CKP sensor is an inductive sensor that allows the ECM to determine the angular position of the crankshaft and the engine speed. The CKP sensor is installed in the rear left side of the sump body, in line with the engine drive plate. The sensor is secured with a single screw and sealed with an O-ring. A two pin electrical connector provides the interface with the engine harness. The head of the CKP sensor faces a reluctor ring pressed into the outer circumference of the engine drive plate. The reluctor ring has a 60 minus 2 tooth pattern. There are 58 teeth at 6° intervals, with two teeth removed to provide a reference point with a centerline that is 21° BTDC (before top dead center) on cylinder 1 of bank A. If the CKP sensor fails, the ECM: Uses signals from the CMP sensors to determine the angular position of the crankshaft and the engine speed Adopts a limp home mode where engine speed is limited to a maximum of 3000 rev/min. With a failed CKP sensor, engine starts will require a long crank time while the ECM determines the angular position of the crankshaft. Heated oxygen (HO2S) senso E135522 The heated oxygen sensors allow the ECM to measure the oxygen content of the exhaust gases, for closed loop control of the fuel:air mixture and for catalytic converter monitoring. An upstream heated oxygen sensor is installed in the outlet of each exhaust manifold, which enables independent control of the fuel:air mixture for each cylinder bank. A downstream heated oxygen sensor is installed in each catalytic converter, which enables the performance of the catalytic converters to be optimized and monitored Oxygen sensors need to operate at high temperatures in order to function correctly. To achieve the high temperatures required, the sensors are fitted with heater elements that are controlled by a PWM (pulse width modulation) signal from the ECM. The heater elements are operated after each engine start, once it has been calculated that there is no moisture in the exhaust (between 0 and 2 minutes delay), and also during low load conditions when the temperature of the exhaust gases is insufficient to maintain the required sensor temperature. The PWM duty cycle is carefully controlled to prevent thermal shock to cold sensors. A non-functioning heater delays the sensor‘s readiness for closed loop control and increases emissions. The upstream heated oxygen sensors produce a constant voltage, with a variable current that is proportional to the lambda ratio. The downstream heated oxygen sensors produce an output voltage dependant on the ratio of the exhaust gas oxygen to the ambient oxygen.