Westerbeke 6.5 MCG Service Manual page 67

ON-BOARD DIAGNOSTICS 1 PC INTERFACE SOFTWARE
Pressure (k.Pa) - This is the pressure that exists in the intake
manifold. At no-load the kPa will be lower than at full load.
The wider the throttle plate is open, the closer it gets to
atmosphere which is about 100 kPa. Typically a genset
running at no-load will see a kPa value around 30, while
at
full load it would be around 90 kPa. If the kPa is stuck at
70 and never moves then there is a problem with either the
MAP sensor or the wiring to the MAP sensor, as 70 is a
default value that is in the code.
WB Heater Set-point - This is the set-point in millivolts of
the heater temperature in the Wideband 02 Sensor. Curently
in all the units that do not have an idle mode, the set point
is 893. In other units the set-point will vary but wll be
displayed in this box.
WB Current Temp - This is the actual value in millivolts of ·
the heater temperature in the Wideband 02 Sensor. If the
heater is working properly, you will typically see values stay
within 20 millivolts of the set-point. The higher the number
is, the colder the heater is. 1)rpically a reading in the 4000
area means that the heater is not working at all. If the value
is swinging dramatically above and below the set-point, the
sensor is probably failing. The sensor should be replaced.
Lambda - Lambda represents the ratio of the amount present
in a combustion chamber compared to the amount that
should have been present in order
to
obtain "prefect"
combustion. Thus, when a mixture contains exactly the
amount of oxygen required to bum the amount of fuel
present the ratio will be one to one and lamba will equal
1,000. If the mixture contains too much oxygen for the
amount of fuel (a lean mixture), larnba will be greater then
1,000. If a mixture contains too little oxygen for the amount
of fuel (a rich mixture), Iamba will be less than 1,000.
Perfect combustion requires an air/fuel ratio of approximately
14.7:1 (by weight) under normal condtions. Thus a lean
air/fuel ratio of, say, 16: 1 would translate
to
a lambda value
of 1.088. (To calculate, divide 16 by 14.7.) A lamba of .97
would indicate an air/fuel ratio of 14.259:1 (derived by
multiplying .97 by 14.7).
In our applications we want to see lambda reading around
1,000. Because of the combustion involved this number will
constantly be changing, ideally you should see the value of
lamba fluctuating slightly above and below the 1,000 target.
Immediately after a startup it is typical to see a rich readings
for lambda. This is part of the startup process and usually
takes a couple of minutes for sensors to warm up and take
control of the air fuel mixture.
If you see a problem
in
this area first check the Wideband
heater value to make sure that the heater is working.
Remember that it takes about three minutes after starting an
engine for it to be totally in control. Physically remove the
sensor and check it for corrosion and build up of deposits.
from the water being injected through the exhaust. Salt water
deposited on the senor will be very damaging. If there is any
evidence of build up, replace the sensor.
65
After checking the senor and the genset is running too rich,
ch!!ck the air intake screens and spark plugs to make sure .
they are clean and functioning properly. If the genset is
running too lean, check the fuel )evel_s and the quality of the
fuel. Water in the gas will cause the genset to run Jean.
Lambda PW Trim - Is the fueling trim precentage that the
wideband oxygen sensor is contributing. In most cases 15%
is the maximum. "'
Wideband P, I & D Term - These values are the lambda
value controlling terms. Their job is to keep the lambda
reading at 1,000 by enriching or enleaning the fueling.
Lambda P & I Term - These values are the lambda value
controlling terms. Their job is to keep the lambda reading at
1,000 enriching or enleaning the fueling.
NB SIT - (Narrowband Short Term Trim) If you genset is
equipped with a narrowband oxygen sensor, this will be the
value of its contribution. Max contribustion is 1
%.
Stepper Pos (steps) - The throttle shaft is controlled by a
stepper motor. The value displayed is in steps. Zero steps
being the closed position.-Most units will run at no load in
the 20 to 30 steps range. These values will vary from engine
to engine.
Pulse Width - Is the fueling duration in milliseconds (ms).
The value will be lower at no load than at full load.
lp Current - Is the electrical'value equivalent of the Lambda
reading. There is not much to learn from this number.
Main Fuel Comp
(%) -
Is the fueling compensation that is
derived from a value in the fuel table, which is based on the
engine rpm and the MAP pressure.
Air Temp and Engine Temp Comp
(%) -
Is the fueling
compensation based on the air temperature and engine
temperature. This value can be both positive and negative.
This value is added or subtracted from the main fuel
compensation value.
Frequency Option - Tis the value of the speed selector on
the ECU, whether it is
50
or 60 Hz. Some interfaces may not
show this column but will display the Frequency Option in
the Title area at the top of the
data
log.
The Generator Frequency - Is a function of engine speed.
For most applications,
50
Hz operation is with an engine
speed of 1500 rpm, while 60 Hz operation is with an engine
speed of 1800 rpm. Note:
Belt drive applications will be
different, check your owners manual for engine speed.