KIT-MODULE-INLET 3900695 - Caterpillar

Illustration 1 g02398886
Exhaust bypass valve components (typical example)
(1) Exhaust bypass valve
(2) Tubing routed to the aftercooler
(3) Breather The exhaust bypass valve (1) controls the amount of exhaust gas that is allowed to bypass the turbocharger turbine. The exhaust bypass valve diverts the correct amount of to exhaust gas directly to the exhaust elbow in order to maintain the desired boost pressure.Excessive boost pressure can result in engine overheating, detonation, turbocharger surge, and overloading of the engine. The amount of exhaust gas to the turbine wheel is controlled in order to provide the correct boost pressure.
Illustration 2 g02398978
Section view of an exhaust bypass valve
(4) Boost pressure inlet from the aftercooler
(5) Diaphragm
(6) Spring
(7) Adjustment screw
(8) Valve
(9) Exhaust gas flow to the turbocharger
(10) Bypass exhaust gas flow to the exhaust elbow
(11) Atmospheric pressure port from the breather Valve (8) is activated directly by the differential pressure between the actual boost pressure and atmospheric pressure.Atmospheric pressure enters through atmospheric pressure port (11) from breather (3). The atmospheric pressure exerts force on diaphragm (5). Force from spring (6) applies pressure to the same side of the diaphragm as the atmospheric pressure. The force of the spring may be adjusted with adjusting screw (7).Opposing pressure is applied to the diaphragm from the boost pressure inlet (4) from the aftercooler. This boost pressure is delivered to the exhaust bypass valve through tubing (1) that is routed to the aftercooler. Additional opposing pressure is applied through the valve stem by the exhaust gas flow from the engine.When the force of the spring plus the atmospheric pressure is overcome by boost pressure and the pressure of the exhaust gas, the valve opens. As the valve opens, bypass exhaust gas (10) flows to the exhaust elbow. The remainder of the exhaust gas (9) flows to the turbocharger. By allowing excess exhaust gas to bypass the turbine wheel of the turbocharger, boost pressure for the engine is regulated to an acceptable level.Under constant load conditions, the exhaust bypass valve maintains a stable position.At full load, the correct position of the exhaust bypass valve will be open by approximately 20 percent.