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Endurant HD N
Overview
The Endurant HD-N transmission and clutch system is designed specifically for
the Cummins ISX12N Compressed Natural Gas (CNG) engine to match the
unique operating characteristics of the CNG engine compared to a diesel
engine.
Drivers will notice a significant difference in operation and performance with the
HD-N and ISX12N combination when compared to the base Endurant HD trans-
mission and diesel engine combination.
Launching and Low Speed Maneuvering
Due to the operating characteristics of a CNG engine, drivers experienced a
delayed input response from the accelerator pedal which affects how the trans-
mission’s clutch controls respond. When the driver depresses the accelerator
pedal there is approximately a one half second delay until the engine responds
and the transmission starts to close the clutch.
To move the vehicle slowly from a stop, the driver needs to slowly depress and
hold the accelerator pedal, less than 50%, allowing the engine time to react to
the input. As soon as the transmission sees the engine responding to the accel-
erator pedal, the clutch begins to close and provides vehicle movement. This
delay in response is also present when releasing the accelerator pedal, as the
engine needs approximately one half second to stop fueling the engine when
the driver releases the accelerator pedal.
Once the clutch has started to close and the vehicle begins to move, if more
power is needed the driver should slowly depress the accelerator pedal a little
more and then hold the position, allowing time for the engine to react to the
input.
The more accelerator pedal input that is provided results in more time required
to bring the engine speed back down to idle and for the transmission to open
the clutch when the accelerator pedal is released. The driver should avoid quick
or rapid changes in accelerator pedal position when attempting to move the
vehicle a short distance to provide smooth and steady operation.
