Systems and methods for counter flow management and valve motion sequencing in enhanced engine braking

A method for controlling counter flow and pressure in an intake flow path of an internal combustion engine during an engine braking operation, the internal combustion engine comprising at least one cylinder, an intake flow path communicating with the at least one cylinder, at least one intake valve disposed in the intake flow path, an exhaust flow path communicating with the at least one cylinder and at least one exhaust valve disposed in the exhaust flow path, the method comprising:

• deactivating main event motion of the at least one exhaust valve;
• initiating activation of an engine braking mechanism associated with the at least one exhaust valve to perform a 1.5 stroke or 2.0 stroke high power density braking operation, the initiating step causing an initial transient state of the engine braking mechanism, during which the engine braking mechanism is not yet capable of causing braking motion of the least one exhaust valve and during which motion of the at least one intake valve tends to permit counterflow from the at least one cylinder into the intake flow path, and thereafter a steady state of the engine braking mechanism, during which the engine brake mechanism is ready to perform engine braking;
• and
• in response to the step of initiating activation of the engine braking mechanism, and during the transient state of the engine braking mechanism, initiating a step of counterflow management and thereby managing counterflow in the intake flow path with at least one airflow management device disposed in at least one of the intake flow path or the exhaust flow path to thereby reduce counterflow that would otherwise be permitted in the intake flow path during the transient state of the engine brake mechanism.