C9 Urban Transit Bus Engine Caterpillar

"Lower Gears Engine RPM Limit"

The engine will accelerate at a slower rate when this limit is exceeded under normal driving conditions. This parameter is used to encourage the driver to shift to the next highest gear.

"Lower Gears Turn Off Speed"

The "Lower Gears Turn Off Speed" parameter is the vehicle speed when the "Lower Gears Engine RPM Limit" is shut off. This must be matched with the "Lower Gears Engine RPM Limit" to the specific drive train for best performance.

"Intermediate Gears Engine RPM Limit"

This parameter is similar to the "Lower Gears Engine RPM Limit". The engine will accelerate at a slower rate when this limit is exceeded under normal driving conditions. This parameter is typically programmed to a slightly higher rpm than the "Lower Gears Engine RPM Limit".

"Intermediate Gears Turn Off Speed"

This parameter is similar to the "Lower Gears Turn Off Speed". This parameter is typically programmed to a slightly higher vehicle speed than the "Lower Gears Turn Off Speed".

"Gear Down Protection RPM Limit"

This parameter is the engine rpm limit when the vehicle speed is above the "Gear Down Protection Turn On Speed". This is a hard limit. The ECM will not allow fuel to the engine above this limit. This parameter is used to encourage the driver to shift into overdrive or top gear.

"Gear Down Protection Turn On Speed"

This parameter is the vehicle speed when the "Gear Down Protection RPM Limit" is turned on. This must be matched to the specific drive train for best performance. Above this "Vehicle Speed Limit", the engine rpm will be limited by the "Gear Down Protection RPM Limit".

"Top Engine Limit (TEL)"

This parameter is the maximum engine rpm when the engine is under load. The engine will still achieve rated rpm under no load conditions.

Note: Select ratings have a different "Top Engine Limit".

"Low Idle Engine RPM"

The "Low Idle Engine RPM" is the minimum engine rpm.

"Transmission Style"

This parameter is used to tell the ECM the type of transmission that is installed in the vehicle. This parameter is used by the ECM to read the signals from the following devices:

• Brake switch (No. 2)

• Clutch switch

• Neutral switch

The ECM must be programmed to one of the following options if an Allison Wt Automatic Transmission transmission is installed:

• AT/MT/HT option 1

• AT/MT/HT option 2

• AT/MT/HT option 3

• AT/MT/HT option 4

If any other automatic transmission is installed, this parameter should be programmed to one of the following options:

• Automatic Option 1

• Automatic Option 2

• Automatic Option 3

• Automatic Option 4

If one of the manual options is selected, terminal J1/P1:24 must receive a signal from a clutch pedal position switch or a message from a clutch switch from one of the supported J1939 sources. If one of the transmissions with a neutral switch is selected, terminal J1/P1:62 must receive a signal from a transmission neutral switch or a message from a neutral switch from one of the supported J1939 sources. If one of the transmissions with two brake switches is selected, the second brake switch must be connected to terminal J1/P1:64.

"AT/MT/HT Part Throttle Shift Speed"

Allison Wt Automatic Transmissions require an input from the ECM to regulate the transmission shifting. The ECM monitors the accelerator pedal position, engine speed, vehicle speed, load, cruise control status and neutral switch status in order to determine if the transmission should use closed throttle or full throttle shift modulation. The "AT/MT/HT Part Throttle Shift Speed" parameter provides three different settings for shift modulation.

Programming the "Transmission Style" to "AT/MT/HT Option 1", "AT/MT/HT Option 2", "AT/MT/HT Option 3", or "AT/MT/HT Option 4" activates ECM output 7. This output controls a shift relay that is connected to a modulator in the Allison transmission.

The high setting will cause the transmission to remain in a lower gear longer before upshifting to the next gear. The medium setting is a compromise between the default setting and the high setting.

"Starting Aid Output"

This parameter is used to allow the ECM to determine if conditions are correct for the use of a starting aid (ether).

"Governor Type"

This parameter determines the type of governor that controls the engine. The Full Range governor tries to maintain a constant engine speed for a throttle position. The Min/Max Governor only governs engine speed when the engine speed is at the minimum allowable engine speed or at the maximum allowable engine speed. When the engine is operating between the engine speed limits, the Min/Max Governor tries to keep power constant across the engine speed range.

Illustration 1	g00837953
Graph for the Min/Max Governor

Select "Full Range" for manual transmissions and for electronically shifted manual transmissions. Select "Min/Max" for automatic transmissions.