WEGO Wide-band Exhaust Gas Oxygen Sensor System

How should the wide-band exhaust gas oxygen sensor be grounded on a chassis dyno?

Vehicles operated on a chassis dyno will generate considerable electrostatic charge. The Bosch LSU 4.2 wide-band exhaust gas oxygen sensor used with the WEGO requires a ground connection to the sensor body in order to dissipate electrostatic charge. If the sensor body is not grounded, electrostatic charge will build up until a discharge to the sensor element occurs. This may damage the sensor and input circuitry on the WEGO unit.

We recommend grounding the vehicle to the dyno frame while in operation. You can use a length of 16 AWG wire with one end secured to the dyno frame and the other end equipped with a heavy duty alligator clip that is attached to the vehicle frame or other vehicle ground point. The dyno frame or chassis must be connected to building electrical ground in accordance with National Electrical Code (NEC) requirements. Improper grounding will cause serious problems.

If grounding the vehicle is not convenient, you can use P/N 115011 grounded sensor, P/N 115012 six wire extension cable with ground connection, and P/N 115013 ground wire kit for installation at the WEGO. Refer to the Grounded Sensor Tech Note for details. Call our office at 386-322-7390 to order.

Grounded WEGO Sensor Mounted on Sniffer


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 used the 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? 

All WEGO 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.

For applications 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? 

Bosch 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.

Since 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:

● The 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 section).

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 www.laddinc.com. 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 environments.

Please 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 sensor. 


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 Automotive Exhaust Sniffer Tech Note  and Motorcycle 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 Screamin Eagle Pro Super Tuner, Screamin Eagle Race Tuner (SERT) or Dynojet Power Commander, check out the features of the Daytona Twin Tec Twin Scan Plus. 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 Commander tables.    


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.

Operating Mode

Recommended AFR

Cold Start (first 30 sec)




Part Throttle Cruise


Wide Open Throttle

12.5-12.8 (values down to 11.5 may be used to reduce detonation)


Can the exhaust system affect wide-band AFR readings?

Wide-band systems 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 likely.

Exhaust reversion. 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 Reduce Reversion

Use 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 -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 steel hardware.  

The 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.  

Excessive scavenging. 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?

Conventional (narrow-band) 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 work?

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 techniques.  


Bosch LSU 4 Sensor Element

(Protective Shroud Removed)



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 microcontroller. 

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. 


WEGO Output Versus AFR


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 Pressure Dependency


What are the limitations of the wide-band sensor?

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 turbo. 

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 Dynojet dyno?

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 WEGO 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

Common conversions:

Ppsi = .145038 x PkPa

Pin-Hg = .2953 x PkPa

Pin-Hg =  2.03602 x Ppsi

You can also use our pressure conversion calculator 


How do I setup the analog input scaling in the WEGO software 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)

  Input Voltage Scaled Value
Minimum .30 20
Maximum 4.80 200
Legend MAP (kPa)  


  Input Voltage Scaled Value
Minimum .30 2.90
Maximum 4.80 29.01
Legend MAP (psi)  


Input Voltage Scaled Value
Minimum .30 5.91
Maximum 4.80 59.06
Legend MAP (in-Hg)  


Delphi 3 bar MAP sensor P/N 12223861 (cross reference Wells SU504)

  Input Voltage Scaled Value
Minimum .62 40.1
Maximum 4.82 304.3
Legend MAP (kPa)  


  Input Voltage Scaled Value
Minimum .62 5.802
Maximum 4.82 44.13
Legend MAP (psi)  


  Input Voltage Scaled Value
Minimum .62 11.84
Maximum 4.82 89.85
Legend MAP (in-Hg)  


Delphi 3.3 bar MAP sensor P/Ns 09373269 & 12215049 (cross reference Wells SU1480 and SU1514)

  Input Voltage Scaled Value
Minimum .25 50
Maximum 4.50 333.3
Legend MAP (kPa)  


  Input Voltage Scaled Value
Minimum .25 7.25
Maximum 4.50 48.35
Legend MAP (psi)  


  Input Voltage Scaled Value
Minimum .25 14.77
Maximum 4.50 98.43
Legend MAP (in-Hg)  


How can I identify my Delphi MAP sensor?

You can identify the type of sensor your vehicle is equipped with by referring to the Delphi MAP sensor brochure and referencing it by part number. Individual data sheets can be downloaded from www.powerandsignal.com/Products/Pressure.aspx. Aftermarket replacement parts are available from Wells at www.wellsmfgcorp.com 


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 at www.digikey.com.

SSI P51 Series Pressure Sensor

Use the following scaling for the 15 psia sensor:

  Input Voltage Scaled Value
Minimum 1.00 0
Maximum 5.00 100
Legend MAP (kPa)  


  Input Voltage Scaled Value
Minimum 1.00 0
Maximum 5.00 14.5
Legend MAP (psi)  


  Input Voltage Scaled Value
Minimum 1.00 0
Maximum 5.00 29.5
Legend MAP (in-Hg)  



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 www.digikey.com.


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 Electronics at www.newark.com or similar TDK-LAMBDA DT80PW120C power supply available from Digi-Key at www.digi-key.com

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 www.mcmelectronics.com.  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. Newer WEGO units with display and data logging allow uploading a fuel type selection with the WEGO Log software including user defined fuels. WEGO III and IV units operate over the 0.70-1.33 Lambda range. WEGO 5 units operate over the 0.50-1.33 Lambda range. Corresponding air/fuel ratio (AFR) values are:


WEGO III and IV Series    
Fuel Type Minimum AFR Maximum AFR
Gasoline 10.3 19.5
E10 9.9 18.8
E85 6.8 13.0
Ethanol 6.3 12.0
Methanol 4.5 8.6


WEGO 5    
Fuel Type Minimum AFR Maximum AFR
Gasoline 7.3 19.5
E10 7.1 18.8
E85 4.9 13.0
Ethanol 4.5 12.0
Methanol 3.2 8.6



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

E10 (Stoichiometric Ratio 14.13)

AFR = 1.92 x (Vout + 5)

Vout = (0.52 x AFR)  - 5

0V = 9.62 AFR  and 5V = 19.23 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

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

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 for most applications. 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 concentration.

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 is:

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_Stoich):

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 software to an Excel spreadsheet and then copy and paste from the Excel spreadsheet into the Power Commander (PC) 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 PKWARE Inc. website. 

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" versions: 

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 software, select AFR Data Display. The 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 the WEGO software 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 Correction Data

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 software, select Fuel Percent Correction Display and set the desired wide open throttle AFR target (typically 12.8-13.2 for gasoline). The 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 software 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 software table rows are in 500 RPM increments and my Power Commander (PC) table rows are in 250 RPM increments. What 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 source.

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 point, 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.


How do I use the WEGO on race vehicles with 16 or 18 volt electrical systems?

WEGO units manufactured before 2012 shut down if the battery voltage exceeded 16.5 volts. All new WEGO units operate up to 19.0 volts. If you have an older WEGO unit and your race vehicle has a 16 volt system with an alternator or any 18 volt system, the voltage will exceed the 16.5 volt maximum allowed by the WEGO. The solution is to install some rectifier diodes in-line with the red WEGO power wire to reduce the supply voltage as shown in the figure below. Suitable 6 amp 400-1000 volt rated diodes are available as P/Ns 833-6A4-TP, 833-6A6-TP, and 833-6A6-TP from Mouser Electronics. If you are using multiple WEGOs, each unit will require a separate diode string. When soldering the diodes together in series, leave about 1 inch lead length between diodes for best heat dissipation. 


Diode Installation for WEGO


How can I display throttle position sensor (TPS) values while tuning?

Lascar Electronics (www.lascarelectronics.com) offers a wide variety of inexpensive programmable displays with analog inputs. These displays can be powered from +12 volts and are compatible with standard zero to +5 volt TPS sensors. The customer can easily program an almost infinite combination of styles, legends, colors, and ranges using their free PanelPilot software. Prices start at under $100.00. The SGD 28-M display is shown below. This version is also available in an IP67 rated waterproof housing. For easy hookup to the TPS sensor signal wire, you can use a Pomona insulation piercing test clip as shown on our Diagnostic Tools and Suppliers Tech FAQ and alligator clips for +12 volt power and ground connections. Make the ground connection to the same point where the engine control module is grounded, never to the battery.


Lascar SGD 28-M with Combo Analog/Digital Program Reading in TPS% Units


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