Injection control pressure strategy during activation of an engine retarder

An internal combustion engine comprising:

• a fueling system that utilizes hydraulic fluid under pressure to force fuel into engine combustion chambers;
• an engine control system for controlling various aspects of engine operation including controlling pressure of the hydraulic fluid;
• and
• a mechanism for augmenting back-pressure on the engine in response to a command from the engine control system to retard the engine;
• wherein
• the control system comprises a selector for selecting control of hydraulic fluid pressure from a selected one of plural sources of hydraulic fluid pressure control to the exclusion of other sources of hydraulic fluid pressure control,
• the one source is selected by a command given in conjunction with the command for the mechanism to retard the engine,
• and in consequence of its selection, the one source controls hydraulic fluid pressure such that the hydraulic fluid pressure is attenuated to, and then kept from exceeding, a defined dwell pressure, and after elapse of a dwell time defined by an amount of time during which the actual hydraulic fluid pressure has not exceeded the defined dwell pressure, the one source increases the hydraulic fluid pressure above the defined dwell pressure.

A method for mitigating the effect of augmented back-pressure on an internal combustion engine fueling system that utilizes hydraulic fluid under pressure to force fuel into engine combustion chambers when a mechanism is operated to augment back-pressure on the engine in response to a command from an engine control system to retard the engine, the method comprising:

• in consequence of issuance of the command to retard the engine, attenuating the hydraulic fluid pressure to mitigate the effect of augmented back-pressure on the fueling system;
• once the hydraulic fluid pressure has been attenuated to a defined dwell pressure, keeping the hydraulic fluid pressure from exceeding the defined dwell pressure;
• and
• upon elapse of a dwell time during which the hydraulic fluid pressure has not exceeded the defined dwell pressure, increasing the hydraulic fluid pressure above the defined dwell pressure.