Engine Output Derating Function; Automatic Warm-Up Function - Komatsu WA250-6 Shop Manual

SEN03834-01

Engine output derating function

If the engine controller detects a failure, it pro-
q
tects the engine by derating the engine torque
or speed.
Following figure shows the engine torque per-
q
formance when the torque was derated.
A: Derated to approximately 30% of the maximum
torque point
B: Derated to approximately 50% of the rated out-
put point
Following figure shows the engine torque per-
q
formance when the engine speed was derated.
A: Derated near to the engine speed at maximum
torque point
28
10-920

Automatic warm-up function

1
When starting the engine in a cold district, this
q
function warms it up by increasing the engine
low idle speed.
If the coolant temperature is below 20°C at
q
starting of the engine, this function increases
the low idle speed to 1,000 rpm. The condition
required for increasing the low idle speed
depends on the coolant temperature as shown
in the figure below.
The automatic warm-up function is reset and the
engine speed returns to 825 rpm as any of the fol-
lowing conditions is met.
The coolant temperature reaches 30°C or
Condition 1 above while the automatic warm-up
function is enabled.
The accelerator pedal angle remains at
Condition 2
70% for 3 seconds or more.
The automatic warm-up function remains
Condition 3
being enabled for 30 minutes or more.
The directional lever or directional
selector switch is set to "Forward" or
"Reverse" while the automatic warm-up
function is enabled.
Condition 4
(When the directional lever and directional
selector switch are returned to "Neutral" to
stop the machine, the automatic warm-up
function restarts.)
920 Electrical system, Part 2

Engine output derating function

WA250, 250PZ-6
1