System for controlling valve timing of an engine with cylinder deactivation

Abstract

Various systems and methods are disclosed for carrying out combustion in a fuel-cut operation in some or all of the engine cylinders of a vehicle. Further, various subsystems are considered, such as fuel vapor purging, air-fuel ratio control, engine torque control, catalyst design, and exhaust system design.

Description

BACKGROUND AND SUMMARY [0001] Engines are usually designed with the ability to deliver a peak output, although most engine operation is performed well below this peak value. As such, it can be beneficial to operate with some cylinders inducting air without fuel injection, and other combusting air and injected fuel, as described in U.S. Pat. No. 6,568,177. [0002] However, the inventor herein has recognized that when using exhaust gas recirculation in such a system, one may need two EGR systems (one for each group of cylinders) so that EGR is not fed to the cylinders not carrying out combustion coupled to a catalyst such as a three way catalyst. This is because if EGR is fed to the cylinders not carrying out combustion, emissions in the EGR can exit untreated depending on the type of exhaust system, such as in a case where each group has a separate exhaust path to the atmosphere. Thus, if only one EGR valve is provided, in some cases, only one cylinder group can ever operate in the cy...

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Benefits of technology

[0016] An advantage of such operation is that overall system performance can be improved, since cylinder valve operation can be selected based on more than providing efficient fuel usage and low emissions for the combusting cylinders. For example, cylinder valve operation can also be selected taking into account the deactivated cylinders, such as pumping loss of deactivated cylinders not carrying out combustion. In other words, since the first and second group are governed by the same cylinder valve actuator (in one example, they would have the same cam timing, such as for a v-8 engine wher

Problems solved by technology

The inventors herein have further recognized other disadvantages with prior variable cam timing approaches when applied in a system that disables fuel injection to cylinders.

Specifically, disadva

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