Here you can find the information you need about wideband theory.


Two basic functions performed by an engine management system (EMS) are to provide a SPARK AT THE RIGHT TIME (IGNITION TIMING) and to meter FUEL IN THE RIGHT QUANTITY (FUEL INJECTION).

ENGINE SPEED from the RPM sensor and ENGINE LOAD from the throttle position sensor or MAP sensor drives the injection and ignition. There are two maps for engine tuning. Fuel map is for injector timings and ignition map is for ignition timings. Also known as serial port tuners or OBD port tuning uses the OBD port to gain access to the maps via an interface. For ECU remapping, one should replace the factory EMS with an after-market EMS. ECU tuning software such as EFILIVE or MegaSquirt is a great tool with a data logger (datalogger) to increase the performance of an engine.

FUEL INJECTION system has fuel tank, fuel filter, fuel pump, injectors and pressure regulator for fuel return. IGNITION system use intake ir temperature sensor to "correct' the air/fuel mixture for different air temperatures since the air density fluctuates when temperature changes. It can also use exhaust gas temperature (EGT) sensor to measure the temperature of the outgoing gases inside the header tube. Especially useful for drag racing since too lean shows higher, too rich shows lower degrees.

APSX WIDEBAND is the only company for wideband AFR controller gauges with Bosch LSU 4.2 wideband O2 sensor that lets the user to calibrate the sensor on the field. Otherwise the sensor wear will result in off readings and will get worse for every hours being used, if you do not calibrate it by periodically.

APSX WIDEBAND also provides the fuel options from lambda to AFR. Such as gasoline (A), lambda (L), E85 (E), diesel (d) and methanol (n). The user can change the fuel type anytime by using the gauge button.



Do you want to monitor the digital readings of the wideband controller? You need digital connection. Please use APSX WIDEBAND Digital Output Software.

The APSX WIDEBAND custom software can be used for digital output out of APSX D1 or D2 products. The GREEN and BLACK wires should be connected to PIN2 and PIN5 of DB9 connector respectively as shown in the picture above. .
Alternatively a DB9 to USB adapter can be used to connect to a USB port of a computer.

Do you want to datalog the analog output of the wideband controller? You need analog connection. However, please do not try this without an aftermarket ECU installed onto your vehicle. Because it does not make any sense.

The DATAQ MODEL DI-145 four-channel USB Data Acquisition Starter Kit can be used for ANALOG output out of APSX D1 or D2 products. The WHITE wire should be connected to an EMS system such as Megasquirt directly or by using DATAQ as shown in the picture above. DI-145 comes with WinDaq Data Acquisition and Playback Software.

Only looking at AFR data will not give any conclusion about the performance of the engine. Again, please do not try this without an aftermarket ECU installed onto your vehicle. Because it does not make any sense. It is always a smart idea to log Air-Fuel-Ratio (AFR) against one of the followings:

  • Manifold Absolute Pressure (MAP)
  • RPM
  • Intake Air Temperature (iat sensor)
  • Others such as throttle position


Is your alternator robust and in good shape? A defective and old alternator can cause a lot of headache due to the several reasons behind the scene. Have your alternator checked before you start your tuning project.

We simulated a "bad alternator" in house as you see below and got 888 on D2 display. As you can see, the voltage line supposed to be a straight line on oscilloscope but it was not and causing the D2 not to function properly.

Then we used a large capacitor seen below in between the D2 and the battery. Negative side of the capacitor was connected to "ground-black" and the other side was connected to "power-red". The suggested common value for the capacitor is 3300 uF, 50V. Never use a capacitor with less than 35V. You can purchase on our website under accessories section:
Larger values may be needed depending on how bad the power fluctuations are on the vehicle. Typically most of the motorcycles experience this alternator issue.

After capacitor application here is the snapshot of the simulated voltage back to acceptable levels. This application is strongly suggested for motorcycles and carbureted engines.

See the youTube video below:

Alternator Diode Testing:


We still believe LSU4.2 market is much bigger. Plus it is more reliable when you perform open air calibration rather than relying on self calibration. So to your question, Not so soon.

Ignition timing, engine tuning, ecu tuning, ecu tuning software, engine management system, traqmate, efilive, apexi, boost controller, mtx, data logger, datalogger, methanol injection, egt sensor, adjustable pressure regulator, fuel management system, digital vacuum gauge, temperature gauge, harry's lap timer, obd-ii port, obd port, psia pressure.

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