SYSTEM AND METHOD USING SECONDARY AIR PUMP FOR SECONDARY AIR INJECTION INTO TURBOCHARGED INTERNAL COMBUSTION ENGINE EXHAUST AND FOR TRANSIENTLY AUGMENTING ENGINE BOOST PRESSURE, INCLUDING MEANS FOR SUPRESSING SURGE OF THE SECONDARY AIR PUMP

In a turbocharged internal combustion engine system including an eCompressor as a secondary air pump (SAP) for injecting air into an exhaust system of the ICE, controllable valves enable the turbocharger compressor and the SAP to provide two-stage compressed air to the intake of the ICE in certain operating conditions, or to feed the air via a secondary air injection line (SAI line) into the exhaust system in other conditions. A conduit is tapped off the discharge of the SAP and connects with discharge ducting from the turbocharger compressor, and an on/off valve configured for defined leakage in the "off' position controls flow through the conduit. When the air from the SAP is needed only for injection air, the leakage through the leaky valve into the intake system suppresses surge of the SAP.