Theory of Operation
The ISM control system gives you a choice between an Automotive and a Variable Speed Accelerator. The choice determines the "feel" of the accelerator pedal and should be made with vehicle configuration and operator preference in mind. Some vehicles are equipped with a cab switch that can be used to select the desired accelerator type. The system also supports the installation of a remote accelerator pedal in specialty applications and can even deactivate the accelerator pedal under desired conditions.
The Automotive Accelerator gives the performance you are used to having with Cummins engines. With this choice, accelerator pedal position determines the engine's torque output (half accelerator position will give you 50% of the engines available torque). If the operator desires more torque to resume a constant speed while climbing a hill, they must depress the accelerator pedal. Using this accelerator type, the accelerator pedal will "feel" the same as your automobile. If the vehicle is equipped with an automatic transmission, the selection of the Automotive Accelerator type is required.
With the selection of the Variable Speed accelerator type, the accelerator pedal position determines engine speed rather than torque output (half accelerator position will give you 50% of the engine's rated RPM). The engine will hold the desired speed under varying load conditions by changing fueling. The Variable Speed Accelerator operates in a similar manner to the "All Speed" accelerators used in the past.
Switchable Accelerator Type
Vehicles may be equipped with a switch to change the Accelerator type. There are no required programmable parameters for this feature. The OEM must correctly install the switch and associated wiring to enable. If the vehicle is equipped, the operator may change accelerator types with the flip of a switch. Some operators may choose to change accelerator types under specific driving conditions, but most importantly, the feature gives the vehicle flexibility. Many operations require vehicles to be driven by more than one operator. In this case, each driver can adjust the accelerator type to their preference. This increases operator comfort and satisfaction.
Some specialty applications require the operator to have pedal activated speed control away from the vehicle cab. In these applications, use of a remote accelerator pedal is common. The ISM control system is capable of supporting the installation of a secondary accelerator pedal. The Remote Accelerator feature must be enabled and the OEM must correctly install the pedal, switch, and associated wiring. Depending on the application requirements, the OEM can setup the hardware to activate the remote accelerator pedal with the same or opposite accelerator type as the cab accelerator pedal. If the vehicle is equipped with a cab switch to select accelerator types, the switch may also be used to change the accelerator type of the remote accelerator pedal.
Vehicles may be setup to disable the accelerator pedals (cab and remote) under desired conditions. The ISM engine is capable of disabling the accelerator pedal based on a switched input. There are no required programmable parameters for this feature. The OEM must correctly install the hardware and associated wiring to enable. The most typical application for this option is the school bus. When the bus door is open, a switched input alerts the control system, thus disabling the accelerator pedal.