940 SE L4-2320cc 2.3L SOHC Turbo VIN 87 B230FT (1991)
Wastegate: Description and Operation
Wastegate Diaphragm And Valve
PURPOSE AND LOCATION
To regulate the maximum charge pressure, the turbo charger incorporates a wastegate valve. When the turbo boost pressure gets too high, the wastegate
valve opens a by-pass around the turbine wheel, reducing the exhaust gas pressure in the manifold. This results in lower turbo rotor speeds and lowers
the boost pressure in the intake manifold.
CONSTRUCTION
The wastegate consists of the wastegate valve (flap type) and diaphragm. The diaphragm is linked to the wastegate valve via an adjustable rod.
One side of the diaphragm chamber is connected, through a vacuum hose, to the pressure side of the turbo charger compressor wheel. The other side of
the diaphragm is spring loaded, keeping the wastegate valve shut.
OPERATION
As the intake manifold pressure rises, the pressure on the diaphragm pushes against the diaphragm spring. When intake manifold pressure acting on the
diaphragm is greater then the pressure of the spring, the wastegate valve opens, allowing exhaust gas to bypass the turbine wheel.
Wastegate Valve W/ Engine At Idle
At idle and partial engine loads, the turbo charger air pressure in the intake manifold is low and the wastegate valve stays shut.
