Driver/Vehicle Information Display: Description and Operation

Display Mode Format:

Mode Select:

DISPLAY
The Trip Calculator shall calculate and display the following vehicle parameters: Instantaneous Fuel Economy, Average Fuel Economy, Range, Elapsed Time, Average Speed, External Temperature, Fuel Used, and Trip Odometer. Only one of the above parameters will be displayed at a time. The Mode Indicator next to the corresponding graphics will be lighted. The display is vacuum fluorescent with 6 characters, 7 segment and parameter units. The display format for each mode is indicated below.

IMPORTANT: When a range of less that 40 miles is calculated, the numeric display will spell "LO FUEL."

DIMMING CONTROL
Display dimming for the Trip Calculator shall be as follows: with Park Lamp Signal (CKT 9) active the vacuum fluorescent display shall make a step dim to half brightness. Further dimming is controlled by the Analog Dim Signal (CKT 230). Incandescent backlighting must use the Pulse Width Module (PWM) Dim Signal (CKT 308).

OPERATION
The user can change the parameter displayed by depressing the "MODE" button located on the Trip Calculator face. The operator can change the display units from English to metric by pressing the "E/M" button on the face of the Trip Calculator.

IMPORTANT: The "E/M STATE" output may be used by other displays in the vehicle to set their display units. The trip calculator must remember the state of the switch from the last ignition cycle.

The Trip Calculator shall perform error detection where possible (no serial data stream for 10 seconds, an open/short circuited Temp Sensor, or an open circuited fuel level sender). If the Trip Calculator is unable to calculate a value due to any missing data, it shall display a flashing "0" when the mode is selected.

EXTERIOR TEMPERATURE
Exterior Temperature shall be calculated and displayed by reading the Outside Air Temperature Sensor. The Trip Calculator shall average increasing temperatures over a 5 minute interval and decreasing temps over a 1 minute interval. The display shall contain a hysteresis of 2°F (1°C). The reset button has no effect while in the exterior temperature mode.

TRIP ODOMETER
The trip odometer is the accumulated mileage since the last trip reset. The trip odometer is reset to zero by pressing "RESET" during the trip mode, a trip reset, or a battery disconnect/reconnect. The display shall rollover at its upper limit value of 9999.9 to 0.0 miles or kilometers.

ELAPSED TIME
Elapsed Time (E/T) is Ignition "ON" time since last reset. E/T is reset to zero by pushing the reset button while in the ELAPSED mode, a trip reset, or a battery disconnect/reconnect. The Trip Calculator must retain E/T during Ignition "OFF." The Trip Calculator shall display the time in seconds for 99:59:59 after which it shall reset itself (roll over to zero).

INSTANTANEOUS ECONOMY
Instantaneous Fuel Economy (IFE) is calculated as the ratio between the accumulated distance since the last IFE update and the accumulated fuel consumption since the last IFE update (Distance/Fuel used). The IFE does nor reset. A fuel consumption of zero will result in a IFE of zero.

AVERAGE ECONOMY
Average Fuel economy (AFE) is calculated as the ratio between the accumulated distance since last AFE reset and the accumulated fuel consumption since last AFE reset (Distance/Fuel used). Upon a reset condition, the reset button pushed during the AFE mode, a trip reset, or a battery disconnect/reconnect, the AFE shall zero out both accumulated distance and accumulated fuel consumption. The Trip Calculator must retain AFE during Ignition OFF."

AVERAGE SPEED
Average Speed (AS) shall be calculated and displayed on Ignition "ON" time and distance traveled since the last average speed reset. Average speed display shall be updated every 10 seconds. Average speed shall reset both the accumulated distance and Ignition "ON" time by pressing "RESET" during the average speed mode, a trip reset, or by battery disconnect/reconnect. Average speed is the ratio of accumulated distance over accumulated Ignition "ON" time, both calculated since the last average speed reset. The Trip Calculator shall retain the average speed values during Ignition "OFF."

TRIP CALCULATOR FUEL USED
The Trip Calculator shall calculate and display the total amount of fuel used since the last fuel used reset. Fuel used shall be the accumulated injector "ON" time since reset, multiplied by the injector calibration constant and scaled to represent gallons or liters, as required.

RANGE
Range is calculated as the product of the Average Fuel Economy (AFE) multiplied by the amount of fuel remaining in the tank (AFE x Fuel remaining). When a range of less than 40 miles is calculating the low fuel range mode is entered, except during the first 10 miles following the AFE reset. During these first 10 miles, the low fuel range mode ("LO FUEL" message) shall not be entered and the range of values shall be 0-999.

During the low fuel range mode the numeric display will spell "LO FUEL" and extinguish the "MI" or "km" units. After the low fuel range mode is first entered, the message shall be flashed at a 2 Hz rate for 60 seconds then displayed continuously. If the range mode was not selected by the driver upon entering the low fuel range mode, then the Trip Calculator shall override the mode being displayed and select the range mode. The driver may however override the low fuel range mode by selecting another mode. If the Ignition is cycled the Trip Calculator shall re-enter it as if it calculated it for the first time.

The fuel sender input is a voltage vs. gallons (fuel level) curve generated by a 0 to 90 ohm variable sender located in the fuel tank and pulled up to Ignition at the Instrument Cluster. The RANGE algorithm must filter the fuel tank sender input over at least a 2 minute average. Hysteresis shall be applied where applicable. The reset button has no effect while in range mode. Range is reset by an AFE reset.

TRIP RESET
The Trip Calculator shall reset the Average Fuel Economy, Elapsed Time, the Average Speed and the Trip Odometer when the "RESET" button is pressed continuously for 5 seconds while in any of these modes. This will be signified to the driver by lighting the Average Fuel Economy, the Elapsed Time, the Average Speed and the Trip Odometer mode indicators, display of "0.0" and extinguished units display for a minimum of 2 seconds or until the operator releases the "RESET" button, whichever is longer. After trip reset, the Trip Calculator shall return to the mode previously selected.