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Underdog Racing Development Performance Calibration Unit

Air/Fuel Ratio Calibrator

For engines with Air/Fuel Ratio Sensors

• Increase part throttle power and torque in boost
• Suited for normally aspirated engines converted to forced induction.
• Suited for late model factory forced induction vehicles
• Reduce exhaust gas temperature in part throttle boost
• Improve engine life

Do you like the idea of boosting your engine at a lean 14.7:1 air fuel ratio?  Of course you don't. This is a problem for many vehicles when a normally aspirated engine is converted to forced induction. 

Your engine is seeing significant boost while the ECU is still operating in CLOSED LOOP mode.  In CLOSED LOOP mode the ECU will fight very hard to keep the mixture at 14.7:1.  That can make the engine knock prone and drive up exhaust gas temperature thus reducing the service life of the engine.

On older vehicles we have the ability to alter CLOSED LOOP mode fuel mixture equipped with O2 sensors.  This was done with the ESC1 box, O2 Sensor Calibrator, or the URD Fuel/Timing Calibrator with the EGO conditioner built in.

Starting in 1999 in the 4Runner and 2000 in the Tacoma, Toyota started using a new type of sensor in lieu of the old O2 sensor.  This new sensor is called an Air/Fuel Ratio sensor.  Air Fuel Ratio Sensors are replacing O2 sensors to more accuratly measure AFRs.

We have a new technology that allows us to change the CLOSED LOOP AFR mixture.  This is done by interfacing with the new style Air/Fuel Ratio sensor and recalibrating it with a 3 dimensional map table based on RPM and manifold pressure.  This is extremely precise and repeatable.  If you want the mixture to richen in boost you can now do this in CLOSED LOOP prior to your entering OPEN LOOP.  If you want the mixture to be 13:1 at 3 PSI; you can set it as such. If you want the AFR to blend to 12.9:1 at 5 PSI, you can do that too.

The beauty of this is this Air/Fuel Ratio Calibrator is that the ECU still thinks the mixture is 14.7:1.  You can now have a very smooth and seamless transition from a boosted CLOSED LOOP to wide-open throttle OPEN LOOP.

The URD AFR Calibrator could be used by its self or with your current fuel controller.  However it is best used in conjunction with a MAF signal calibrator like our URD Fuel/Timing Calibrator.

The URD AFR Calibrator will work on numerous vehicles including all Toyota engines equipped with Air/Fuel Ratio sensors.  The unit is dual channel and will also work on engines with two front Air/Fuel Ratio sensors like the 1GR-FE 4.0 V6 engine.

The URD AFR Calibrator will not work on an engine that has an old style O2 sensor.  For those vehicles please consider one of our EGO Calibrators.

The AFR Calibrator ships tuning software with a vehicle specific installation guide for most compatible Toyota vehicles.  The unit will have a start up map preloaded that is specific for the 5VZ-FE engine with the TRD supercharger, or the unit will be set to a neutral setting.

(If you have a 1999 or 2000 California 4Runner, please select other, and tell us what you have.)