VH TRIP COMPUTER
GENERAL INFORMATION
The trip computer which is fitted to SL/E models (as a delete option) and optional equipment on SL/X models consists of five major components:
- Display module
- Function module
- Electronic control module
- Fuel flow sensor
- Speed sensor
All functions with the exception of the clock are derived from one or both sensors.
DESCRIPTION & OPERATION
The computer will display seven different pieces of information via the
four digit, seven segment, red light emitting diodes in me left fland module
called me display module (Fig 12-7). The display module
contains four press buttons which have a detented momentary contact action.
The two extreme buttons are the 'Reset' and 'Select' buttons which are used
most often and for this reason are protruding. The two inner buttons are used
to set the time and calibration numbers and are almost flush with the module
surface to prevent accidental operation These buttons are activated via a pencil
or similar pointed instrument, such activation being facilitated by recesses
in the button surfaces Functions available and shown on the function module
(Fig 12-8) are:,
- Clock
- Distance to empty (km)
- Distance travelled for trip (km)
- Average speed for trip (km/hour)
- Instantaneous fuel usage (litres/100 km)
- Average fuel usage for trip (litres/100 km)
- Total fuel used for trip (litres)
The functions are called up in sequence by depressing the 'select' button i.e. each time the 'select' button is pressed the function, as listed above, will increment by one
While the 'select' button is depressed the display will show zero.
When ignition is turned on the 'clock' function will be displayed irrespective of what function was being used at ignition turn off
To reset the computer both 'reset' and 'select' buttons must be pressed simultaneously. Tflis will reset all functions to zero with the exception of 'clock' and 'distance to empty'.
If when resetting, the select button makes contact prior to the reset button, the function will increment by one. When the battery is first connected it may be necessary to 'reset' the computer to get it working normal
CLOCK
The clock is a 12 flour clock with a flashing decimal point
When the battery is first connected, the clock will show 12.00 and appropriate setting is achieved by depressing the right hand flush button for minute adjustment and the left hand flush button for hours adjustment.
It is suggested that minutes be adjusted prior to hours because as the minutes pass 60 the hours number automatically increments by one.
The clock can be accurately set as the next minute will not display until 60 seconds after releasing the adjustment button
DISTANCE TO EMPY (DTE)
The distance to empty function is an estimate on how much further the vehicle
can be driven on the fuel remaining in the tank, based on the rate of fuel usage
for the previous 15 minutes. The readout is in whole numbers Only. The DTE function
can only be an estimate based on previously obtained information. For this reason,
as conditions become more suited for economical driving, the distance to empty
can actually increase, for example. from city to highway driving. A built-in
safety feature allows up to 30 km of driving under highway conditions after
DTE shows zero, however,due to tolerance variat:ons on the components from which
the computer derives its information, this figure will vary from vehicle to
vehicle The computer has electronic damping to flatten Out fluctuations of fuel
level in the tank and rate of fuel usage and will update the readout after consumption
of 0.32 litres of fuel approximately. Due to the large fuel level fluctuations
whilst mobile, the readings are heavily damped and averaged over a long time
- up to half hour. This does not matter during normal operation but after a
fuel fill a long delay to display a sensible DTE is not acceptable. so with
a fil of 10 litres or more the computer wiil calculate a higher DTE from a short
average at the next normal update and the long averaging will proceed from the
new figure.
DISTANCE TRAVELLED/CALIBRATE
This function reads distance travelled in kilometres since the computer
was reset showing to one decimal point up to 100 and whole numbers thereafter.
The calibrate function s designed to allow a very accurate distance calculation
and is entered as follows.
a.Line up vehicle against known marker e.g. centre pillar against major highway marker.
b.Press left hand flush button and display will go to zero,
c.Drive off and the display will increment in whole numbers.
d.Stop vehicle exactly 10 km from starting point i.e. centre pillar against major highway marker 10 km from original marker.
e.Press right hand flush button.
When button is released, distance travelled since reset will display and the last number shown will enter computer memory as the calibration number The calibration number should be between 615 and 650 for standard vehicles however special tyres, gearbox, axle. tyre pressures, vehicle loading etc. will have a bearing on this number. Depressing the right hand flush button any time the distance travelled/calibrate function is called up will display the calibration number.For those who do not wish to have this degree of accuracy (1 metre in 10 km) or who do not have access to an accurately measured 10 km an approximate number of 625 is used for distance calculations.
Whilst in the calibrate mode i.e. after the left hand flush button is pressed and prior to depression of the right hand flush button, the 'select' button is disconnected as selection of other functions during the calibration procedure would affect the calibration number and computer distance functions would be inaccurate.
AVERAGE SPEED
The average speed reading measures average speed since the computer was
reset and only calculates this average speed whilst the ignition is on. To enable
the computer to collect enough data to calculate a sensible speed, the display
will show zero for the first minute after reset. Reading is updated at one minute
intervals.
INSTANTANEOUS CONSUMPTION
The instantaneous fuel consumption function reads in litres/100 km in whole
numbers only and updates at half second intervals. When the vehicle is stationary
the display shows zero, however, when slowing down to a stop, due to fuel being
used and a small distance being travelled, some large numbers may be displayed.
Also when the funtion is first called up some large numbers may appear due to
the small time frame over which the computation is prepared
AVERAGE CONSUMPTION
The average fuel consumption reads in litres/100 km and calculates fuel
usage since last reset and updates at approximately one minute intervals.
FUEL USED
Total fuel used since reset is measured in litres to a maximum of 999 litres.
TRIP COMPUTER COMPONENTS
DISPLAY MODULE
The display module is a snap fit into the facia panel. Figs. 12-9
and 12-10.
The functions of the display module are outlined under Description and Operation.
Make sure on installation that yellow identification marks on upper side of
module and connector body match up.
FUNCTION MODULE
The function module consists of 7 red light emitting diodes which illuminate
to show the appropriate function selected. The illuminated function light will
dim when the instrument panel lights are switched on.The module is a snap fit
into the facia panel.Make sure on installation that yellow identification marks
on upper side of module and connector body match up, Figs. 12-9
and 12-10
ELECTRONIC CONTROL MODULE
The electronic control module is fitted to the right hand side of the firewall
behind the instrument carrier assembly. It is necessary to remove the
lower instrument panel trim to gain access to the module, Fig.
12-11 - When installing connector body to module, ensure that yellow identification
mark is to the top. The electronic control module should only te replaced when
sender or sensor checks prove satisfactory.
FUEL FLOW SENSOR
Principle of OperationThe fuei flow sensor assembly incorporates a wire
mesh fuel strainer at the inlet, a fuel vapour/liquid return port, a diaphragm
compartment, and the flow transducer Vapour bubbles which enter the unit with
the gasoline accumulate at the top of the fuel return port where they can be
returned to the fuel tank through a built-in orifice which will limit the return
of fuel if no bubbles are present The vapour return orifice diameter is 1.5
mm on LA and L6 engines and 1.04 mm on V8 engines. Inside the diaphragm compartment,
a rubber diaphragm is arranged perpendicular to the fuel flow entering the diaphragm
compartment. The flow transducer is arranged with its inlet upstream and outlet
downstream of the diaphragm This arrangement isolates the transducer from fuel
flow pulsations and minimizes errors due to different transducer response times
for flow changes The flow transducer has a circular rotor compartment with a
tangential inlet and and axial outlet at the top Vapour bubbles which enter
this compartment are separated and vented. The rotor speed is sensed by an opto-electronic
emitter-detector pair which are isolated from the fuel and placed outside the
path of vapour bubbles to minimize optical interference. For installation of
the fuel flow sensor, see Figs 12-12 (Starfire 4), 12-13 (173 6cyclinder),
12-14 (202 6 Cylinder)
and 12-15 (V8).
SPEED SENSOR
The speed sensor consists of a magnetic coil and is fitted to the rear of
the speedometer and senses the speedometer's magnetic coil operation The speed
sensor is included in all 8VX instrument clusters
FUEL LEVEL SENSOR
The fuel to empty is sensed by the fuel gauge tank unit resistance reading
The tank unit resistance may be checked in the normal manner should any query
arise as to readout on display module and actual fuel gauge reading.Figure 12-8
Function Module