Group 25 Intake and Exhaust System Design and Function
Exhaust Pressure Governor
The exhaust pressure governor(EPG) acts as an exhaust
brake when slowing the vehicle down. It also speeds en-
gine warm-up by applying a load to the engine during
idle and warm-up. Engine load is created by the (EPG)
throttling the flow of exhaust gases, causing the engine
to work against a backpressure. This increases combus-
tion temperature and shortens the warm-up period.
On engines without a pre-heater, the (EPG) is activated
before the starter motor is engaged. For engines with a
pre-heater, the (EPG) is activated after pre-heating,
start-up and post-heating have taken place.
The (EPG) is activated by a control pressure of about
200 kPa (29 psi), by a combi relay when it is used during
starting and warm-up. When used for engine braking,
the exhaust pressure governor is controlled by a single
two-position switch if the engine is equipped with an ex-
haust brake only, and by dual two-position switches if the
engine is equipped with a Volvo Engine Brake, or VEB
(both exhaust brake and compression brake).
T2006948
Fig. 17: Exhaust pressure governor (EPG)
Engines with Exhaust Brake Only
Two-position switch (ON/OFF)
With the switch in the ON position, the exhaust pressure
governor is activated by a control pressure of approx.
750 kPa (110 psi) subject to the following conditions:
•
Accelerator pedal fully up.
•
Clutch pedal fully up.
•
Engine speed above 1100 rpm.
•
Boost pressure below 52 kPa (7.5 psi).
•
When using cruise control and preselected road
speed is exceeded by 7 km/h (4 mph) (disengage-
ment at 4 km/h (3 mph) over preselected speed).
•
ABS not activated (continuous control).
W2000731
Fig. 18: Exhaust brake switch for WX, WG and AC
W3001324
Fig. 19: Exhaust brake switch for VN/VHD
19
To Next Page
Loading...
