Introduction to Maserati
4200 Wet Sump Engine
SECONDARY AIR SYSTEM
2
2
4
3
1.
Solenoid valve
2.
Pneumatic valves
3.
Vacuum tank
4.
Secondary air pump
1 The secondary air system used on the wet sump engine is modified with respect to the dry sump engine. The secondary air is now inserted in the specific ducts in the cylinder heads to improve warming up of the catalityc converters and reduce further emissions. Through the solenoid valve (1) the Motronic ECU controls opening/closing of the two pneumatic valves (2) that activate injection of secondary air directly into a channel machined into the engine head casting. The flow continues along its path through the communication holes between the channel and the exhaust duct to reach the exhaust manifold. The vacuum tank (3) that accumulates the vacuum necessary to open the pneumatic valves is positioned in the engine compartment underneath the secondary air pump. The secondary air pump (4), controlled by the engine ECU, sends air to the exhaust ducts. The pump and the secondary air solenoid valve are activated, after engine ignition, when the coolant temperature is in the range -7 °C and +40°C. The temperature threshold of 40°C disables the operating of the system. During the system operating cycle, the seal of the secondary air valves is checked. Throughout the cycle, the oxygen sensors are in “open loop” configuration and therefore do not activate the feedback for A/F ratio correction.
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