FMX Drive By Valve (DBV) Speed Limiters

A mechanical speed limiter is used by vehicles with mechanical accelerator pedals.

DBV components include: 

  • ECU (Electronic Control Unit) 
  • FCU (Fuel Control Unit) 
  • Speed Sensors

Functions Of FMX DBV Speed Limiters

Assume the Speed is set to 80 km/h.

  • The vehicle will run up to 79 km/h, and when it reaches 80 km/h, the Mechanical Speed Limiter DBV will kick in.
  • A speed signal is received from the speed sensor that is connected to the ECU, and when the set speed has been achieved, the information is sent to the FCU, which will then regulate the fuel flow to the engine.
  • A key advantage of our system is that we have a bypass system built-in that will maintain the vehicle's speed.
  • The FCU will automatically open once the vehicle reaches the set speed, allowing for smooth operation.

A Reference to the FMX DBV Speed Limiters Parts


Speed Limiters are brains formed by ECU 


A factory-programmed microcontroller determines what functions are to be performed at each stage of the process.

ECU has three connectors as described below.

  • Power Supply Input
  • Speed Sensor Input
  • Fuel Control Unit (FCU) Output

Mounting of ECU

  • Install the ECU in a suitable position within the cabin of the vehicle.
  • Connect the Power Supply Harness to the ignition system of the vehicle.
  • Make sure that the red wire is connected to the positive supply & black should be grounded to the vehicle metallic body.
  • Check the LED's work when the ignition key is in the 'On' position and vice versa while the power supply is connected to the ECU 
  • Our ECU  is now operational.

Understanding the Fuel Control Unit (FCU)


The FCU is divided into two chambers. Automatically, one is controlled by the ECU and the other manually, by adjusting the bypass screw. When the bypass screw is fully open, the speed limiter's control is reduced, and vehicles tend to move faster.


The vehicle will not be able to control smoothly if the bypass screw is fully closed. Therefore, it needs to be adjusted after completing the vehicle road test.


Find a suitable location to fix the FCU near the engine:

  • The FCU should be installed between the fuel filter and the FIP on diesel vehicles.
  • In a petrol engine, the FCU should be connected to the pressure line very close to the injector.
  • The unit will be supplied with special hoses and connectors, and the connection must be made according to the arrow markings
  • The FCU's wire should be routed safely and connected to the ECU.
  • Check if the FCU is functioning by turning on the ignition. There will be chattering sounds coming from the FCU.
  • Our FCU is now operational.

Understanding the speed sensors


An ECU uses the speed pulse signal from the speed sensor to determine & control the vehicle's speed.


New Generation Vehicles: 

New generation vehicles will have electronic speed sensors near the gearbox. Such cases can be handled using an electronic sensor adapter / SSW, which converts the vehicle pulse to a square wave pulse, which is compatible with the ECU.


Old Vehicles: 

In vehicles equipped with mechanical speedometers, we need to use mechanical speed sensors, which can be classified into three categories.


JIS Sensor

DIN Sensor


Hino Sensor


Mounting of the Speed Sensors


Install the speed sensor between the gearbox and speed-ometer cable of the vehicle, and ensure both ends are securely tightened. The sensor wire is routed safely to the cabin and connected to the ECU.


We can tap the signal wire from the vehicle speed sensor and connect it to our ECU. The Electronic Sensor Adaptor/SSW converts any waveform into square wave pulses.