WEGO Wide-band Exhaust Gas Oxygen
How does Daytona Sensors test
WEGO systems and sensors?
Daytona Sensors is the
only company offering test services for wide-band systems and Bosch LSU 4.2
sensors. If you are an ISO9000 company, professional racer, or serious tuner
using one of our WEGO systems, we can provide a test certificate that the
system and sensors are within specification.
WEGO systems are tested on a PC based automated test
system. Sensors are testing using a known good WEGO in a three step process:
1. One or two (for dual channel systems) sensors are
mounted on a test manifold. The sensors are allowed to reach normal
operating temperature and a free air calibration is performed at the WEGO to
establish the free air operating point. Sensors with gross defects will fail
during this test step.
2. Lab grade nitrogen gas is used to simulate the
stoichiometric operating point (zero oxygen and zero hydrocarbon level
corresponding to 1.00 Lambda).
3. A Bosch specified
reference gas (3.15% hydrogen, 3.15% carbon dioxide, and 4.05% carbon
monoxide with balance nitrogen) is used to simulate the 0.8 Lambda (11.74
gasoline AFR) operating point. This reference gas is supplied by Air Liquide
Specialty Gases Division. Outside of the major automotive companies and
institutions such as Southwest Research Institute, Daytona Sensors is the
only company in North America currently purchasing this reference gas. You
can draw your own conclusions.
WEGO Sensor Test Manifold
Reference Gas used for WEGO Sensor Tests
What is the difference between
the five generations of WEGO units?
The first generation WEGO (originally sold
by our sister company Daytona Twin Tec) used
a Honda/NTK L2H2 wide-band sensor and did not have any built-in data logging
capability. The WEGO II series was a second generation product. The WEGO II
new Bosch LSU 4.2 wide-band sensor and included built-in data logging. The
Bosch LSU 4.2 wide-band sensor was available at a much lower cost than the
earlier Honda/NTK part. The result was that we were able to offer the WEGO
II for substantially less than the price of the original unit.
The third generation WEGO III
series is packaged in an improved low profile housing. WEGO III units with
display and data logging use an ultra-bright daylight readable blue LED
display that is water-proof and include a built-in USB interface. The older
WEGO II units had a red LCD display that was prone to moisture intrusion and
used an RS-232 serial data interface.
The fourth generation WEGO IV
series is packaged in an aluminum housing intended for under dash or dyno lab
environments. WEGO IV units are not sealed.
The WEGO 5 is a dual channel unit with
internal data logging. It features both CAN data bus and analog air/fuel
ratio outputs. It does not have a built-in display.
From an operational standpoint,
the WEGO II, WEGO III, WEGO IV, and WEGO 5 units are similar.
What is the advantage of the
free-air calibration feature on WEGO units?
systems provide quick and easy at-a-glance verification and adjustment of the
sensor free-air calibration. This allows the WEGO to maintain accuracy
as the sensor ages and maximizes sensor life in racing applications where the
sensor may be exposed to leaded fuels.
using unleaded fuels, free-air calibration should be performed on initial
installation and whenever a sensor is replaced. Periodic free-air
calibration is generally not required. When used with leaded racing fuels,
free-air calibration should be performed at the beginning of each race event
or dyno tuning session. When free-air calibration is no longer possible, the
sensor has reached end-of-life and must be replaced.
Why do WEGO systems use a
Deutsch connector in place of the Bosch connector on the wide-band sensor?
LSU 4.2 sensors come with several styles of proprietary connectors. A common
style is shown below. The Bosch connector includes a calibration resistor
that establishes the nominal free-air calibration. This approach is required
for original equipment applications. Obviously it would not be feasible to
manually adjust the free-air calibration for each sensor installed on a
vehicle assembly line.
all WEGO units have a free-air calibration adjustment (as explained in the
previous section), the Bosch connector with its built-in calibration
resistor is not required. There several reasons why we use a Deutsch DT
series connector in place of the Bosch connector:
mating Bosch connector that would be required on the WEGO wire harness is
bulky and expensive
The Bosch connector requires a special crimping tool
whereas the Deutsch DT series are widely used in automotive racing and most
professional mechanics already have the proper crimping tool. Race car and
dyno room installations that require routing custom length cables through
small firewall openings and then installing the connector are considerably
easier with the Deutsch connectors.
Using the Deutsch connectors facilitates installation of our prefabricated
extension harnesses. Simply plug the extension harness between the WEGO and
the sensor. This would not be possible with the Bosch connector.
The customer can easily replace a failed sensor with any
available Bosch LSU 4.2 series part. The Deutsch connector housings can be
reused many times, only new terminals are required (as explained in the next
Wide-Band Sensor Connectors
Can I supply my own
replacement sensor or extension wire harness?
Yes. The new WEGO units use a
Bosch LSU 4.2 sensor that is readily available from your local VW dealer or
Bosch parts distributor. You must replace the Bosch connector with a six
terminal Deutsch connector. You can reuse the connector housing. You can order
terminals and extra connector housings from Ladd Industries at
You can also make your own
extension harness. Click on the links below for the appropriate drawings. You
should use a proper Deutsch crimping tool. If you use a generic "open barrel"
crimping tool, you must also solder all the terminals.
WEGO LSU 4.2 Sensor Drawing
WEGO Extension Harness Drawing
What kind of engines can I tune
with the WEGO?
The WEGO system can be used
to tune most four stroke gasoline powered internal combustion engines:
Motorcycles with carbureted or
fuel injected engines. WEGO III P/N 112001 is intended for motorcycle
applications. The WEGO is an ideal tuning aid, either for on-road or
dyno tuning. Knowing the exact air/fuel ratio greatly simplifies the task
of carburetor jetting.
Automotive applications. WEGO III P/N
112002 has an extended
length harness. WEGO IV P/N 114001 is intended for under dash or dyno lab
note that the WEGO cannot be used with two stroke or marine engines where
oil or water vapor in the exhaust would cause serious problems with the
Can I use the WEGO in place of
an expensive exhaust sniffer when dyno tuning?
Regardless of what some people
may claim, it is impossible to properly tune a fuel injection system or
carburetor on a modified engine without some means of exhaust gas analysis.
Shops can use the WEGO as a low cost alternative to expensive systems such
as those sold by Dynojet®. You can easily fabricate your own exhaust sniffer to
use with the WEGO, eliminating the need to install weld nuts in the exhaust
(refer to our
Exhaust Sniffer Tech Note
Exhaust Sniffer Tech Note
for details). The disadvantage is that you won't have AFR data on the Dynojet®
chart or be able to directly link to a Power Commander®.
If you are using the
Pro Super Tuner, Screamin
Race Tuner (SERT) or Dynojet® Power Commander®, check out the features of
the Daytona Twin Tec
The Twin Scan II software analyzes logged data and displays AFR and the
required volumetric efficiency (VE) correction (in percent) with the same RPM
rows and throttle position sensor (TPS) columns used in SERT and Power
What AFR values are optimum when
tuning an engine?
Higher AFR values correspond to
a leaner (less fuel) condition. The practical operating range for most engines
using gasoline fuel is from approximately 11.5 to 14.7 AFR. Combustion of a
stoichiometric mixture (exactly enough air to burn all the fuel) results in
14.7 AFR indication. Automotive engines with catalytic converters operate near
14.7 AFR during cruise and idle. Race engines require a richer mixture to limit cylinder head temperature and
prevent detonation. The table below lists recommended AFR values for race engines
without emission controls.
Start (first 30 sec)
(values down to 11.5 may be used to reduce detonation)
Can the exhaust system affect
wide-band AFR readings?
will give inaccurate AFR readings in certain situations:
Excessive exhaust back pressure. Wide-band sensors are
affected by back pressure. Excessive back pressure causes exaggerated AFR
indications under rich and lean conditions, but has little effect at 14.7
AFR (stoichiometric). The WEGO is intended to be used with a free flowing
performance exhaust. Overly restrictive stock mufflers may cause excessive
back pressure under wide open throttle. When used with a turbo system, the
sensor must be mounted downstream of the turbo. Motorcycle exhaust systems
are relatively free flowing and problems with exhaust back pressure are not
Reversion is the term for a negative pressure wave that can suck ambient air
back into the exhaust and cause an erroneous lean AFR indication. Exhausts
without mufflers, such as open headers or "drag pipes" on
motorcycles, usually suffer from reversion effects and may not be suitable
for use with the WEGO. Reversion effects will also occur with certain
exhausts used on "bagger" style motorcycles, where two pipes split
off near the rear cylinder. At
part throttle, air is actually sucked into the left tailpipe. Reversion effects will be most noticeable
at idle, part throttle low RPM cruise, and decel.
WARNING: If you can
insert a broomstick through the mufflers, you have the equivalent of open
drag pipes and the WEGO sensors will not read accurate AFR values.
You can reduce reversion
effects in open drag pipes and mufflers without restrictive baffles with the
modification shown below.
Exhaust Mod to
washers with an OD that is 2/3 to 3/4 the ID of the pipe (for example,
1-1/2” OD washers are suitable for pipes with an ID of 2” to 2.25”).
Weld ¼-20 socket head cap screws to the washers as shown. Drill holes at
the bottom of the pipes about 2” from the end and use decorative acorn
nuts to secure the washer assemblies. We suggest that you use stainless
washers will reflect positive pressure waves that will cancel out the
negative pressure waves reflecting from the end of the pipes. You can turn
the washers just like throttle blades to provide more or less restriction.
Dyno tests will show a significant increase in midrange torque and a small
drop in top end horsepower as the restriction is increased.
Turbo systems or tuned exhausts in combination with a high overlap camshaft
profile can force unburned air and fuel mixture through the cylinder into the
exhaust and cause an erroneous rich AFR indication. For motorcycles, some
aftermarket 2-into-1 systems such as the Thunderheader appear to suffer from this
problem, whereas others such as the Vance & Hines Pro Pipe and White
Brothers E-series seem less affected.
Misfiring. If the AFR is
so rich that the engine misfires, high levels of oxygen will remain in the
exhaust gas and result in an erroneous lean indication.
What is the difference between a
wide-band and conventional exhaust gas oxygen sensor?
exhaust gas oxygen sensors have been widely used in automotive applications
since 1981. Conventional sensors have one to four wires and can only sense
air/fuel ratio over a relatively narrow 14.5 to 15.0 range. They are intended
to be used with 3-way catalytic converters that require operation near the
stoichiometric point (14.7 air/fuel ratio). The range of narrow-band sensors
is inadequate for performance tuning. While originally developed for lab and
specialized automotive applications, wide-band sensors are ideal for tuning.
The 5-wire Bosch LSU 4.2 sensor used with the WEGO operates over a range of
10.3 to infinite air/fuel ratio.
How does the wide-band sensor
The Bosch LSU 4.2 wide-band
sensor integrates a conventional (narrow-band) heated oxygen sensing Nernst
cell with an oxygen pump cell. With an appropriate electronic interface such
as the WEGO, this integrated sensor element is capable of measuring the
air/fuel ratio (AFR) of hydrocarbon fuels over a very wide range. For more
detailed information, you can read the
Bosch LSU 4.2 specifications.
It is important to understand
that the wide-band sensor is measuring the apparent AFR based on the
composition of the exhaust gas. The actual AFR is the mass of air divided by
the mass of fuel inducted into the engine. For any given AFR, the
concentrations of the various exhaust gas constituents can be measured under
experimental conditions or calculated using computer programs based on
chemical kinetics. Under rich conditions, excess hydrocarbons and carbon
monoxide remain in the exhaust gas. Under lean conditions, excess oxygen
remains in the exhaust gas. Earlier generations of exhaust gas analyzers were
based on measuring the carbon monoxide level using infrared absorption
LSU 4 Sensor Element
Diagram of Bosch
LSU 4 Sensor and WEGO Circuitry
The Bosch LSU 4 wide-band
sensor element consists of a heater cell, conventional (narrow-band) oxygen
sensing Nernst cell (with associated reference cell exposed to ambient air),
and an oxygen pump cell. The three bottom cells (heater, reference, and Nernst)
are identical to a conventional heated narrow-band oxygen sensor (4-wire type)
widely used in automotive applications since the 1980s. As shown in the graph
below, the VSENSE output of the Nernst cell is exactly 0.45V at the
stoichiometric AFR (14.67 for gasoline). In the Bosch LSU 4, the Nernst cell
compares the partial pressure of oxygen within the pump cell cavity to ambient
air (outside the sensor). The sensing range of the Nernst cell is relatively
narrow - the output is linear from about 14.5-14.9 AFR.
Bosch LSU 4
Nernst Cell Output Versus AFR
Exhaust gas continually
diffuses into the pump cell cavity through a small diffusion gap. The pump
cell can also pump oxygen into or out of the cavity depending on the direction
of current for the IPUMP terminal (the fifth wire for a 5-wire wide-band
sensor). When IPUMP is negative, oxygen is pumped into the cavity. When IPUMP
is positive, oxygen is pumped out of the cavity. The pump control loop (shown
as summing junction and operational amplifier) maintains the pump cell cavity
at stoichiometric conditions (VSENSE=0.45V).
If the pump cell cavity becomes
slightly rich, VSENSE increases and the pump control loop makes IPUMP negative
to pump oxygen in. Under rich conditions, this oxygen is generated by
electrochemical decomposition of water and carbon monoxide in the exhaust gas
at the surface of the pump cell. Chemical reactions between the excess
hydrocarbons, carbon monoxide, and pumped oxygen then restore stoichiometric
conditions within the cavity.
If the pump cell cavity becomes
slightly lean, VSENSE decreases and the pump control loop makes IPUMP positive
to pump excess oxygen out. The pump control loop is a feedback and control
system that maintains stoichiometric conditions in the pump cell cavity as the
exhaust gas AFR changes. The relationship between pump current and exhaust AFR
is shown in the graph below. If the exhaust gas is already at stoichiometric
AFR, no oxygen pumping is required to maintain the cavity at the
stoichiometric point and IPUMP=0.
Bosch LSU 4
Oxygen Pump Current Versus AFR
The digital signal processing (DSP)
block changes the non-linear relationship between oxygen pump current and AFR
into a linear 0-5V output as shown in the graph below. The DSP block also
filters the oxygen pump current signal to remove noise. The WEGO implements
both the pump control loop and DSP functions in firmware that runs on an Atmel
The DSP block also includes a
control loop that maintains the heater cell at 750 deg C. Pulse width
modulation (PWM) turns the heater current on and off at a 30 Hz rate. The PWM
duty cycle (percent of time that current is on) determines the average heater
current. The resistance of the Nernst cell is inversely proportional to
temperature. Additional circuitry (not shown) measures the Nernst cell
resistance. The resistance value is used as feedback for the heater
temperature control loop.
The Bosch LSU 4 wide-band
sensor is affected by exhaust pressure as shown on the graph below. The error
(%) applies to the oxygen pump cell current. Note that 1 bar corresponds to
normal sea level atmospheric pressure. For most performance applications,
excessive exhaust back pressure is not a concern and the resulting small error
can be disregarded. At high elevations, the error is also relatively small. At
10,000 feet elevation (about .68 bar), AFR values near 13.0 will be shifted up
approximately +0.15 AFR.
Bosch LSU 4
What are the limitations of the
The sensor will be quickly
degraded if leaded racing gasoline is used. Under these conditions, expected
sensor life will be less than 10 hours. As the sensor degrades, free air
calibration will become impossible.
Oil or other hydrocarbon
residues in the exhaust will affect the sensor readings. Likewise, gasoline
containing ethanol will result is slight air/fuel reading errors.
The sensor responds to the
partial pressure of oxygen. Excessive exhaust back pressure will affect sensor
readings. This should not be a problem with any performance exhaust system.
When used with a turbo, make sure the sensor is located downstream of the
Make sure that power is on to
the WEGO whenever the engine is run. Without power to the internal heating
element, the sensor will clog with hydrocarbon residues and may be permanently
degraded. If you want to remove the sensor, we sell an 18 x 1.5mm hex plug.
Can the WEGO be interfaced to a
Yes. You can easily interface
any of the WEGO systems to a Dynojet® dyno equipped with the Dynojet® analog
module. If you interface the WEGO IIID, you can display and chart two channels
of AFR data along with the other dyno data in the Dynojet® WinPEP® software. For
complete details, please refer to the
Dynojet® Interface Tech Note.
What units are used to measure
pressure and how do I convert values?
Three units are commonly used
for pressure values: pounds per square inch (psi), inches of mercury (in-Hg),
and kilopascals (kPA). Most original equipment data sheets and service
manuals now use kPA as the unit of measurement. A standard atmosphere (atm) is
the mean sea level pressure at 60°
F. The unit bar (1 bar = 100 kpa) is also encountered in descriptions of
manifold absolute pressure sensors and is just under one atmosphere.
Standard atmosphere (atm) =
14.696 psi = 29.92 in-Hg = 101.325 kPa
Ppsi = .145038 x PkPa
Pin-Hg = .2953 x PkPa
2.03602 x Ppsi
You can also use our
pressure conversion calculator
How do I setup the WEGO Log
software analog input scaling to correctly display pressure for Delphi 2, 3 or
3.3 bar MAP sensors?
Note that all values are based
on a +5.0 volt reference supply to the MAP sensor.
Delphi 2 bar MAP sensor P/N
09350899 (cross reference Wells SU1477)
Delphi 3 bar MAP sensor P/N
12223861 (cross reference Wells SU504)
Delphi 3.3 bar MAP sensor P/Ns
09373269 & 12215049 (cross reference Wells SU1480 and SU1514)
How can I identify my Delphi MAP
You can identify the type of
sensor your vehicle is equipped with by referring to the
MAP sensor brochure
and referencing it by part number. Individual data sheets can be downloaded from
Aftermarket replacement parts are available from Wells at
How do I connect a manifold
absolute pressure (MAP) sensor on a race vehicle without an ECM?
If the vehicle does not have a
factory ECM that provides +5 volt power for a standard automotive type MAP
sensor, you can use an industrial sensor, such as the SSI Technologies P51
series. These can be powered directly from +12 volt and provide a 1-5 volt
output. P/N P51-15-A-UB-I36-5V-000-000 has a 0-15 psia range and is suitable
for normally aspirated engines. Other versions with higher pressure ratings
are available for boosted applications. These sensors are available from Digi-Key
SSI P51 Series Pressure Sensor
Use the following scaling for the 15 psia sensor:
My vehicle doesn't have an
electrical system to power the WEGO. What can I do?
An easy solution is to use a
small 12 volt sealed lead acid battery and battery charger. Panasonic P/N
LC-R123R4P is a small (5.3"L x 2.6"W x2.4"H) 12 volt 3.4 amp-hour
battery that will power a WEGO for over an hour. The Patco P/N 3202P
charger will recharge the battery in about 2 hours. You will also require the
Patco P/N 4010P hookup cable. These parts are available from Digi-Key at
What type of power supply can I
use to power WEGO systems on my dyno?
For single or dual channel WEGOs,
you can use the ELPAC FWA065012A-11B 12 volt 6 amp supply available from Newark
www.newark.com or similar TDK-LAMBDA DT80PW120C power supply
available from Digi-Key at
ELPAC Power Supply
For eight channel dyno
installations using four WEGO IIID systems, you can use the Tenma 72-7670
25 amp power supply available from MCM Electronics at
The Tenma unit is adjustable from 3-15 volt and should be set to 13.8 volt
when used to power multiple WEGO units. It
can also be used to float charge a 12 volt battery.
Tenma Power Supply
Can I use the WEGO with other
fuels besides gasoline?
Yes, the WEGO system will work
with most hydrocarbon fuels including ethanol, E85, and methanol. Special WEGO
III units are available with the display calibrated for methanol fuel. WEGO data
logging software now supports multiple fuel types including user defined fuels
and allows proper chart display of AFR values
for all WEGO models with internal data logging. All WEGO units have a 0-5V
output that can be interfaced to data acquisition or dyno systems. The scaling
is the same for all WEGO models. Scale factors are listed below for common fuels
(Vout is the WEGO output voltage):
Gasoline (Stoichiometric Ratio 14.69)
AFR = 2 x (Vout + 5)
Vout = (0.5 x AFR) - 5
0V = 10 AFR and 5V = 20 AFR
Ethanol (Stoichiometric Ratio 9.01)
AFR = 1.227 x (Vout + 5)
Vout = (0.815 x AFR) - 5
0V = 6.14 AFR and 5V = 12.27 AFR
E85 (Stoichiometric Ratio 9.77)
AFR = 1.33 x (Vout + 5)
Vout = (0.752 x AFR) - 5
0V = 6.65 AFR and 5V = 13.3 AFR
Methanol (Stoichiometric Ratio 6.47)
AFR = 0.881 x (Vout + 5)
Vout = (1.135 x AFR) - 5
0V = 4.4 AFR and 5V = 8.8 AFR
Pump gasoline is now often E10 fuel or other ethanol
blends with up to 10% ethanol. This can be treated the same as standard
gasoline. While the actual stoichiometric ratio is slightly lower and varies
with seasonal blends, you can tune using common gasoline AFR target values
such as 12.8 AFR at wide open throttle. The WEGO will always display 14.7
AFR at the actual stoichiometric point for the fuel, regardless of ethanol
The WEGO sensor is a lambda sensor, where lambda is the
technical term for a dimensionless fuel/air ratio. Lambda 1.00 is the
stoichiometric point (where there is sufficient oxygen to react with all the
available fuel) for any fuel. The output of the WEGO at lambda =1.00 is
2.345V for any hydrocarbon fuel. The output of the WEGO in terms of lambda
lambda = 0.1361 x (Vout + 5)
Vout = (7.345 x lambda) - 5
0V = 0.681 lambda and 5V = 1.361 lambda
For other fuels not listed above, you can use the
universal formulas given below if you know the stochiometric air/fuel ratio
AFR = AFR_Stoich x (Vout + 5)/7.345
Vout = (7.345 x AFR/AFR_Stoich) - 5
0V = 0.681 x AFR_Stoich and 5V = 1.361 x AFR_Stoich
How can I use Excel
spreadsheets with the Dynojet® Power Commander®?
If you have Microsoft Office with Excel, you
can directly copy and paste data from the WEGO Log software to an Excel
spreadsheet and then copy and paste from the Excel spreadsheet into the Power
program. We have prepared sample Excel spreadsheets that you can download and
use for this purpose. Before you try using this approach,
you need to make a realistic assessment of your skill level as far as using
Excel. Please note that we cannot provide tech support for Excel
related issues or help you with individual tuning files. However, since this
approach is new, we do appreciate comments, suggestions, and feedback.
The sample Excel spreadsheets are in a ZIP archive file that you
can download by clicking on the link below. You will require PKZIP to unzip
the individual files within the archive. If you do not have PKZIP installed on
your computer, you can download it from the
Sample Excel Spreadsheets for use with the WEGO system (about 40 K)
The current version 3.2.1 of
the PC software supports copy and paste operations. Some earlier versions do
not. Spreadsheets for use with the WEGO system and PC have a filename
starting in "WEGO_PC." The first type (with "AFR" in the
filename) has corrections based on WEGO AFR data. The second type
(with "Fuel" in the filename) is based on WEGO fuel percent corrections.
Standard spreadsheet table rows are in 500 RPM increments. For PC tuning
files that utilize table rows with 250 RPM increments, use the "Advanced"
spreadsheets and read the additional notes below. Use the following guidelines to choose between "AFR" or "Fuel"
PC Corrections Based on WEGO AFR Data
This approach is recommended for only for
applications without original equipment oxygen sensors where you want to
change AFR values. In the WEGO Log software, select AFR Data Display.
The WEGO Log table will show the actual AFR values logged by the system.
Start the PC program and open the Excel spreadsheet. The first sheet is Base
Fuel values. Copy the fuel table values from the PC to the Base Fuel sheet.
The second sheet is WEGO AFR Data. Copy the AFR Data from WEGO Log
to the WEGO AFR Data sheet. The third sheet is Target AFR. Edit the values
in this sheet to your desired target AFR values. The last sheet is Corrected
Fuel. These are the calculated fuel values required to achieve the target
AFR values. Copy the corrected fuel values back into the PC. The cells in
this last sheet have calculation formulas. Be careful not to type anything
into these cells as this will corrupt the formulas.
PC Corrections Based on WEGO Fuel Percent
This approach is recommended for all
applications with original equipment oxygen sensors. Remember that with
these applications, closed loop AFR control in the ECM will counteract any
attempt to change AFR values at idle and part throttle. Use this approach to
keep the existing AFR values commanded by the ECM at idle and part throttle, but make corrections for
engine modifications at wide open throttle (60% to 100% TPS columns). In the
WEGO Log software, select Fuel Percent
Correction Display and set the desired wide open throttle AFR target
(typically 12.8-13.2 for gasoline). The WEGO Log table
will show the fuel corrections required to achieve the
target AFR value. Start the PC program and open the Excel
spreadsheet. The first sheet is Base Fuel values. Copy the fuel table values
from the PC to the Base Fuel sheet. The second sheet is WEGO Fuel Correction.
Copy the fuel percent correction data for the 60% to 100% TPS columns from
WEGO Log to the WEGO Fuel Correction
sheet. Leave the 0% to 40% columns blank. The last sheet is Corrected Fuel. These are the calculated fuel
values required to achieve the target AFR value. Only the values in the 60%
to 100% TPS columns will change. Copy the corrected fuel
values back into the PC. The cells in this last sheet have calculation
formulas. Be careful not to type anything into these cells as this will
corrupt the formulas.
WEGO Log software table rows are
in 500 RPM increments and my Power Commander® (PC) table rows are in 250 RPM
can I do?
Logging data with 250 RPM increments is very
difficult. The problem is obtaining enough samples in each cell to calculate a
reasonable average when engine RPM is rapidly changing. In most cases, you can
find a basic PC table that has 500 RPM increments. If your application
requires a PC tuning file with table rows in 250 RPM increments, you can use
our "Advanced" spreadsheet versions. These allow copy and paste of fuel table
data from and to the PC software with table rows in 250 RPM increments while
still using WEGO data with table rows in 500 RPM increments. The advanced
spreadsheets calculate interpolated fuel correction values for the
intermediate 250 RPM rows.
How can I test my WEGO system
including the Bosch sensor?
For a basic quick test, you will require a
12 volt power source, digital voltmeter (DVM), and a small disposable butane
cigarette lighter. If the WEGO has been removed from the vehicle, you can use
a 12V battery as a power source. Do not use a battery charger as a power
Connect the black WEGO
signal and power ground wires to the
battery minus terminal. Connect the red WEGO power wire to the battery
positive terminal (for WEGO IV series, make connections to the terminal
block). Connect the black DVM lead to the WEGO signal ground and the red DVM
lead to the WEGO AFR output (white wire on single channel units, white and
blue wires on dual channel units, or appropriate terminal on WEGO IV
series). Test each channel separately on dual channel units.
With the Bosch sensor in free air, let the
WEGO warm up and then perform the free air calibration procedure (refer to
instructions). The status LED should be blinking rapidly (WEGO IIID) or the
display should indicate FA (WEGO III and IV series units with display) and
the DVM should read +4.95 to +5.05 volts. Use a butane lighter as a
hydrocarbon vapor source. Torch type cigar lighters may not work properly,
use the cheap disposable variety. Do not light the flame. Just hold the
lighter at the tip of the Bosch sensor and spray butane at the sensor. The
voltage should drop below 0.3 volts for WEGO IIID units and 0.25 volts for
WEGO III and IV series with display. If your system passes this test, you
can be 90% confident that it is functioning correctly.
The comprehensive test that we perform in
our lab requires reference gases and a small test chamber for the Bosch
sensor. The test is performed at three points: free air, stoichiometric, and
0.80 lambda (11.75 AFR for gasoline). Ambient air is used to test the free
air point. Lab grade nitrogen gas is used for the stoichiometric point (no
oxygen or hydrocarbons remaining after a theoretically complete combustion).
For details on the Bosch recommended reference gas used for the 0.80 lambda
you can refer to page 9
of the Bosch
LSU 4.2 specifications.
The Bosch recommended reference gas is available from Scott Specialty Gases,
but is very expensive at about $1000 for a C size cylinder.