Methods and systems for operating an engine

Abstract

Systems and methods for improving operation of a hybrid vehicle are presented. In one example, engine operation is adjusted in response to a change in engine operating conditions that result in a fractional amount of cylinder charge comprised of exhaust gas changing by more than a threshold percentage. The approaches describe may improve vehicle drivability and fuel economy.

Description

technical field [0001] The present invention relates to systems and methods for improving drivability and fuel economy of vehicles. This method is especially useful for engines connected to electric motors. Background technique [0002] It may be desirable to operate the engine with a mass of gas drawn into the cylinder containing more than 25% recirculated exhaust gas. Operating the engine with a higher concentration of recirculated exhaust gas increases engine efficiency and reduces the likelihood of engine knock. The engine may be operated at a higher concentration of EGR between a lower intermediate engine load to a higher intermediate engine load. Since combustion stability at lower engine loads and higher EGR rates may be less than expected, the engine may be operated at lower exhaust gas recirculation (EGR) levels at lower engine loads. [0003] During travel from one location to another, the driver may frequently change engine load such that the engine changes fro...

AI Technical Summary

Problems solved by technology

However, the response of the engine EGR valve and the EGR flow dynamics may cause the EGR fraction into the engine cylinder to be temporarily increased when it may be necessary to decrease the EGR fraction into the engine cylinder

So the increased EGR ratio could cause the engine to misfire

Engine emissions and vehicle drivability may be degraded if the engine misfires

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