Abstract: An internal combustion engine having a crankshaft rotatable within an engine block of the engine and at least one camshaft driven by the crankshaft. The crankshaft is fixed to a crankshaft wheel having a plurality of crankshaft wheel marks and at least one crankshaft position indicia. The camshaft is fixed to a camshaft wheel having a predetermined pattern of camshaft wheel marks. A crankshaft sensor is fixed to the engine block for producing a crankshaft signal in response to detection of the crankshaft position indicia. A camshaft sensor is fixed to the engine block for producing camshaft signals in response to detection of the camshaft wheel marks. Rotation of the crankshaft generates a pattern comprising the crankshaft signal and the camshaft signals. A processor compares the generated pattern to a stored reference pattern for determining from such comparison the position of the crankshaft within the engine block.

Abstract: A method and apparatus for desulfating a NOx trap is proposed wherein the SOx purge temperature is achieved by modulating the amplitude of the A/F of the mixture supplied to the engine thereby storing oxygen in the trap during lean engine cylinder events and generating the required exotherm during rich engine cylinder events.

Abstract: A method and apparatus for desulfating a NO.sub.x trap is proposed wherein the SO.sub.x purge temperature is achieved by modulating the amplitude of the A/F of the mixture supplied to the engine thereby storing oxygen in the trap during lean engine cylinder events and generating the required exotherm during rich engine cylinder events.

Abstract: A method and apparatus for desulfating a NO.sub.x trap is proposed wherein half of the engine cylinders are operated at a rich air/fuel ratio and half are operated at a lean A/F during the desulfation process. The two exhaust gas streams, the rich stream and the lean stream, are physically or chemically separated until they enter the NO.sub.x trap. A catalyzed exothermic chemical reaction is then generated in the trap. The resulting temperature increase is sufficient to remove SOX from the trap. During desulfation spark advance is adjusted to minimize event time imbalance.

Abstract: A method and system for controlling combustion stability for a lean-burn engine having a plurality of cylinders including a plurality of cylinder pairs utilizes a speed sensor for sensing an engine speed and generating a corresponding temperature signal and an air flow sensor for sensing a cylinder air mass and generating a corresponding air mass signal. An average event time for each of the plurality of cylinders is determined, as well as an instantaneous variation in event times between each of the plurality of cylinder pairs. An actual level of engine roughness is determined based on the variation in instantaneous event times from the average event times. A desired level of engine roughness is determined based on the speed signal, the air mass signal, and a desired air/fuel ratio.

Abstract: A method and system for determining and controlling air/fuel ratio during lean engine operation relies on applying a small fuel pulse width modulation to the engine and synchronously measuring the effect of the modulation on related engine event periods. This effect is utilized in estimating air/fuel ratio, which is then compared to the desired air/fuel ratio. The difference between the estimated air/fuel ratio and the desired air/fuel ratio is used in controlling the air/fuel ratio to the desired air/fuel ratio.

Abstract: An air/fuel mixture control system for an internal combustion engine uses a closed-loop controller which varies the air/fuel mixture in response to the oxygen level in the engine's exhaust emissions to achieve stoichiometry. The oxygen level sensor produces a binary signal indicating either a rich or a lean mixture. The controller responds by generating a fuel delivery rate control signal which has three components: an integral (ramp function) component, a proportional step function component which abruptly jumps the control signal to an intermediate level at the time of each oxygen level change, and a differential overshoot component which (1) injects a compensating volume of fuel into the engine intake at the onset of each lean signal, and (2) subtracts a compensating volume of fuel from the intake at the onset of each rich signal. The compensating fuel volume minimizes the effects of fuel puddling in the intake manifold to reduce the effective closed loop delay time for better control.