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everal General Motors vehicles are equipped with a 2.2L engine called ECOTEC. This four-cylinder, fourvalves-per-cylinder, all-aluminum power plant was first installed in some Saturn models, beginning with the 2000 L-series. Saturn VUE and ION models followed. It was the optional engine in the 2002 Pontiac Sunfire and Grand Am, Oldsmobile Alero and Chevrolet Cavalier and Malibu, and standard equipment starting in 2003. The ECOTEC is also used in the Saab 9.3. The ECOTEC engine uses a speed density-based fuel injection system, along with a waste-spark electronic ignition system. The waste-spark ignition is part of a unique Compression Sense Ignition (CSI) system that allows the powertrain …ver más…

Over a period of 5 to 10 microseconds, this voltage level becomes high enough to reach the spark plug gap breakdown voltage level. Each spark plug gap breakdown level is determined by the impedance value of the individual spark plug gaps. At the breakdown point, the air gap between the spark plugs’ electrodes will ionize and quickly conduct current, break over and establish an arc across the electrodes. One of the important characteristics of this event is the voltage level at which any spark plug gap impedance will reach its breakdown voltage level. The greater the spark plug gap imped-

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INVESTIGATING GM’S COMPRESSION SENSE IGNITION ance, the greater the voltage level that must be reached for the plug gap to break down. The greater the voltage level required in order to reach breakdown, the greater the required time to reach this voltage level. The spark plug gap impedance is affected by several factors. The greatest variable is the pressure in the cylinder when the spark is generated by the coil. A cylinder on its exhaust stroke has less incylinder pressure than a cylinder on its compression stroke. Remember, a DIS coil releases its energy to two cylinders simultaneously—to one cylinder on its exhaust Fig. 1 stroke, to the other on its compression stroke. However, due to the pressure-related uneven plug gap impedances, both