Exhaust Flap, Position/Task/Design/Function

Exhaust Flap, Position/Task/Design/Function

ENGINE 113.960 with CODE (479) Cylinder shutoff
ENGINE 137.970




21 Exhaust flap (open)
21/1 Exhaust flap diaphragm unit
22 Vacuum reservoir
N3/10 Engine control module (ME-SFI)
Y93 Exhaust flap valve
a to engine
b pressurizing

Location
Between TWC and rear muffler



21 Exhaust flap

Task
To increase the backpressure in the exhaust system, therefore optimizing noise characteristics.

Design/function
The exhaust flap valve is actuated up to approx. 2300-2500 rpm when cylinder shutoff is ON. It opens and vacuum from the vacuum reservoir is applied to the diaphragm unit. The flap in the exhaust pipe closes. The remaining annular gap is still sufficient for the quantity of exhaust gas when cylinder shutoff is ON.
The flap is always open at higher engine speeds.