PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 2/TASK 2
Once this happens and the fluid temperature approaches a predetermined
level, a warning light on the instrument panel indicates that the retarder
operation should be discontinued until the fluid cools down and the warning
light goes out. When the retarder pedal is released, the retarder valve
closes and the fluid in the cavity automatically discharges and permits the
rotor to turn without drag.
d. Jacobs Engine Brake (figure 66). The Jacobs engine brake consists
of a slave piston mounted over the exhaust valve. The system operates by
opening the exhaust valve near the top of the compression stroke. This
releases the compressed cylinder charge into the exhaust system. This
blowdown of compressed air into the exhaust system prevents the return of
energy from the piston on the expansion stroke. The result is an energy
loss because the work done in compressing the charge is not returned to
usable energy. The system is operated by a threeposition switch that
allows the driver to select the degree of braking required. The three
position switch is set to allow braking on two, four, or all cylinders.
This enables the driver to predetermine how much braking will be needed to
stop the vehicle.
FIGURE 66. JACOBS ENGINE BRAKE.