Method and system for binary flow turbine control

A method for a boosted engine, comprising:

• deactivating fuel injection to an engine;
• and
• while the engine spins towards rest,
• adjusting a scroll valve coupled to an outer scroll of a multi-scroll exhaust turbine based on deviation of estimated turbine speed relative to a turbine speed deceleration profile.

An engine system, comprising:

• an engine including selectively deactivatable fuel injectors;
• a turbocharger for providing a boosted aircharge to the engine, the turbocharger including an intake compressor and an exhaust turbine, the exhaust turbine including a first outer scroll and a second inner scroll;
• a scroll valve coupled between an exhaust manifold of the engine and an inlet of the first outer scroll;
• a wastegate included in a bypass coupled between an inlet and an outlet of the exhaust turbine;
• and
• a controller with computer readable instructions for,
• in response to torque demand being lower than a threshold,
• selectively deactivating fuel injection to the engine;
• and
• while the engine spins down to rest, decreasing an opening of the scroll valve, the decreasing based on a difference between an estimated or measured turbine speed and a desired spin-down turbine speed profile during the spin-down.