Yanmar 4BY - Torque Limitation for Overheat Protection

TROUBLESHOOTING
BY Service Manual
13-5
Engine Faults and Torque Limitations
Torque Reduction Chart Based on Intake Air Temperature
The intake air temperature will limit the torque at 3000 rpm if the air temperature is increasing.
Torque Limitation for Overheat
Protection
In the case of this limitation there are two possible
situations:
If an electronic fault occurs, it will be displayed on
the display-alarm and a P-Code is saved in the
system. These codes can be read with a diagnostic
tester. A substitute value (fixed value until fault
disappears) is activated (coolant temp=110,
fuel temp=90) and a torque reduction occurs. In this
case, the coolant temperature is also limited by the
torque limit which is described in Torque Limitation
for Failed Sensors on page 13-3. The substitute
value of the fuel temperature is fixed at 90°C and
that sets a limitation of approximately 75% from the
maximum torque (Figure 13-1).
If the coolant temperature is over 108°C, an audible
alarm sounds and engine overheat is displayed on
the instrument panel display. At 120°C the torque
limitation is 30% (Figure 13-2). If the fuel
temperature is too high (over 90°C) this limitation is
also active for the overheat prevention as shown in
Figure 13-1. From 100 to 140°C the torque limit is
about 40% of the maximum torque. In this case
there is not an alarm on the instrument panel
display. In both cases, no P-Code appears.
Figure 13-1
Figure 13-2
Engine speed 2000 rpm 2000 rpm
Torque Torque [N·m]
Intake air
temperature [°C]
Torque [N·m]
Intake air
temperature [°C]
Engine 4BY150 4BY180
100% (normal operation) 295 30-50 315 30-50
90% 265 60-90 285 60-90
80% 240 100-130 250 100-130
Engine 6BY220 6BY260
100% (normal operation) 450 30-50 450 30-50
90% 405 60-90 405 60-90
80% 360 100-130 360 100-130