Methods and system for central fuel injection

Abstract

The invention provides methods and system for central fuel injection. Methods and systems are provided for adjusting engine operating conditions for reduction of NOx emissions. In one example, immediately after a fuel shut-off event, in response to an oxygen content of an exhaust catalyst being higher than a threshold, manifold charge cooling may be increased by increasing the portion of fuel delivered to the engine via manifold injection relative to the portion to fuel delivered via one or more of port and direct injection. By increasing manifold cooling, NOx production may be reduced.

Description

technical field [0001] The present invention generally relates to methods and systems for adjusting manifold fuel injection to reduce NOx emissions. Background technique [0002] Internal combustion engines may include a central fuel injection (CFI) system that injects fuel into an intake manifold. When fuel is injected into the engine intake, heat is transferred from the intake air and / or engine components to the fuel, and this heat transfer results in atomization of a portion of the fuel, which results in cooling of the engine components. Injecting fuel into the intake air (eg, in the intake manifold, intake port, etc.) reduces both the intake air temperature and the combustion temperature at the engine cylinders. By cooling the intake charge, NOx production can be reduced. NOx is stored in an exhaust catalyst that is periodically or timely regenerated during rich-to-stoichiometric operation. In addition to CFI, fuel may also be injected into the intake runner via port ...

AI Technical Summary

Problems solved by technology

Therefore, emission quality may be adversely affected by

Furthermore, the need for additional fueling to purge the catalyst adversely affects fuel economy

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