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 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.

WARNING: This installation requires WELDING and connection to vehicle electrical system. You can easily damage the parts and cause a fire or explosion if you don’t take proper safety actions. If you don’t know what you are doing and with even a small doubt, DO NOT attempt any installation and get professional help. Even with using an engine tuner professional, it is their responsibility to validate and confirm the vehicle safety for the intended use of this product. APSX WIDEBAND holds no responsibility for any engine damage that results from the misuse or abuse of this product.


• As a general rule, never route the harness close to ignition wires.
• Route the harness very carefully to avoid chafing or undue strain.
• Secure wiring to vehicle with wire ties with special attention to the sensor harness routing beneath the vehicle and in the engine compartment.
• Take care when routing sensor harness near hot exhaust components.
• Use a 5A inline fuse on the switched 12V power supply line (RED - Power/IO).
• Avoid cutting or extending the sensor harness.
• Use appropriate gauge wire (20 AWG or thicker) when extending wires, especially RED (Switched 12V with min 3A) or BLACK (Ground) of the Power/IO harness.
• Ensure all connections are secure and insulated from shorts to adjacent wires and the vehicle structure. Utilize proper crimping and solder/heat shrink techniques.


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.

The digital output is for monitoring the readings from a PC or from APSX G1 LED display. Please refer to drawing on page 2 for digital output connections via DB-9 connector to a PC. Baud rate is 9600 bps, data bits is 8, no parity and stop bits is 1 (9600 8N1).

1- Wire the DB-9 pin numbers 2 and 3.
2- Run application.
3- Select and open the related port.
4- Write some letters on the black area on the software.
5- If you see a repeat of the letters then all is correct. (When you type “A”, it should display another “A” next to it immediately.)

If not, check comport numbers. Go to device manager and change the port number to something lower than 9.

We use single byte protocol. It is not ASCII. If it reads 1 then device is not ready. Otherwise it should read 90 to 190.
90 = 9.0 AFR
190 = 19.0 AFR
147 = 14.7 AFR

This will be only for gasoline even if you change the fuel type to others.

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.

0-5V analog output scaling formula for Gasoline AFR = (2 * Volts) + 9. It is Lambda = (0.136 * Volts) + 0.61.

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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