Effects of Injection Pressure, Intake Throttling, and Cylinder Deactivation on Fuel Consumption and Emissions for a Light Duty Diesel Engine at Idle Conditions 2020-01-0303

The continuing growth of urban population centers has led to increased traffic congestion for which vehicles can spend considerable periods at low speed/low load and idle conditions. For light-duty diesel vehicles, these low load conditions are characterized by low engine exhaust temperatures (~100^oC). Exhaust temperatures can be too low to maintain the activity of the catalytic exhaust aftertreatment devices (usually need >~200^oC) which can lead to high emissions that contribute to deteriorating urban air quality. This study is a follow-on to two previous studies on the effects of throttling, post-injection, and cylinder deactivation (CDA) on light-duty diesel engine exhaust temperatures and emissions. The focus of the present study is on fuel consumption, exhaust temperatures, and emissions with and without cylinder deactivation or with fuel cutout, and the sensitivity to or effects of fuel rail pressure, along with observations of apparent idle engine friction.

The baseline injection strategy was adapted from a 2014 Chevrolet Cruze having an engine similar to the light-duty 2.0 liter GM engine used for this study. All measurements were made under idle conditions and with the engine speed of 850 rpm maintained by adjusting the duration of the main injection.

Deactivated fueling showed a modest improvement in fuel consumption, between 4-16% less than with 4 active cylinders, while CDA achieved a 33% fuel consumption improvement at idle for WOT and about 40% for some throttled cases where pumping losses were greater.

Friction mean effective pressure was found to be greater for the cases with only two firing cylinders compared with normal four cylinder operation and tended to decrease as MAP was reduced, perhaps due to lower piston/cylinder friction.

Exhaust temperature, as measured at the exhaust ports, increased by 20^oC with cylinder deactivation and increased by an additional 25^oC with the deactivated fueling method. Reducing MAP caused the exhausted temperature to increase by as much as 80^oC with all four cylinders active and 95^oC for CDA and for deactivated fueling