Yaroslavl Engine Plant YMZ-536 Operation Manual page 107

When it is necessary to use sustained braking (e.g. for a long-
time downhill movement), the driver, without disengaging the clutch,
cuts off the fuel supply and shifts to the lowest gear. In this case the
engine starts operating as an air compressor, with the rpm depending
on the vehicle movement speed.
When the exhaust brake throttle valve closes the exhaust path,
the exhaust resistance and the brake power are increased.
The exhaust break ("mountain brake") valve has a pneumatic
drive.
It is controlled by means of an electromagnetic valve.
When the throttle valve closes the exhaust path to the
maximum, the backpressure in the exhaust system must not exceed
390 kPa (4,0 kgf/cm
2
).
EXHAUST BRAKE
107