940 SE L4-2320cc 2.3L SOHC Turbo VIN 87 B230FT (1991)
Air Bypass Valve: Description and Operation
Turbo Chargers
The by-pass valve dampens intake manifold pressure drop to prevent surging when the throttle valve suddenly closes at high engine RPM (high turbo
pressure). It is attached to the top of the turbo-charger.
When the throttle valve closes, manifold pressure drops and a pressure shock wave oscillates through the intake system. If not controlled, the air mass
meter would register the oscillating air flow, which would cause the engine to surge. By opening a path from the intake manifold to the turbo charger
inlet, the by-pass valve dampens the shock wave caused by the sudden decrease in pressure.
