Yanmar 6CXM-GTE, Service Manual

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3.11.3 Boost Compensator
The boost compensator, installed to the injection pump of the turbocharged engine models, limits the movement of the fuel con-
trol rack with the boost pressure detection equipment. It optimizes fuel injection and combustion according to the air volume
inside the cylinder for complete combustion and higher output.
(1) Performance
1) The solid line shows the rack's moving distance and the boost pressure when the engine speed is raised gradually.
2) When the regulator handle is raised quickly from the idling position (N0) to the (N1) position, the rack moves from R0 to
R2 to attain the engine speed (N1), and injects a large quantity of fuel. The supply of air, however, is inadequate due to the
follow-up delay of the turbocharger (i.e. insufficient boost pressure), and the exhaust turns black.
3) The boost compensator limits the advancing of the rack and keeps it at R3 position. The rack starts to move at pressure of
PA and reaches to R2 position when pressure rises up to PB or more.
4) In engines with the boost compensator, injection quantity in the range of rack positions R2 - R3 (shadowed area) is lim-
ited and thus black exhaust is controlled.
(2) Equipment
When the regulator handle is operated quickly for acceleration, the control rack moves to the fuel increase side and touches
the boost compensator lever (A) to limit the rack's stroke. This position is the point where about 70% of the max. injection
quantity is obtained. (Fine adjustment is possible by the adjust screw.)
R
R
R
R
R
1
1
2
2
3
0
0
P
P
A
B
P
N N N
Without boost compensator
With boost compensator
Rack position and boost
pressure linear diagram
when engine speed is
raised gradually
Boost pressure
Boost pressure linear diagram
at quick accelaration
Idle
Engine speed
Rack position