Annu Kumar said:
The VEC3 Viper Engine Calibrator allows precise tuning of the air to fuel ratio and ignition timing over the entire operating range of the engine. Simply inserting a pre-programmed Smart Card immediately changes the program settings for the current driving situation or octane of fuel as desired.
The unit contains its own fuel injector drivers and is wired in between the factory PCM and engine. It is especially useful for recalibration of both forced induction engines and those with extensive modifications, allowing the tuner to quickly get the engine running correctly. Stock engines can also benefit greatly from improving the ignition timing and fuel curves.
The VEC3 is similar to a stand-alone engine management system, but also has similarities to a piggyback system. We consider it as working “in series” with the factory PCM.
In a true stand-alone system, you must program for every operating condition the engine will experience, such as load, throttle position, RPM, engine temperature, air temperature, etc. These systems can be quite complex to tune. Most PCM’s also control radiator fan operation, A/C operation, emissions operation and diagnostic functions. Stand-alones are generally not compatible with OBD2 emissions testing in that they replace the factory PCM and will not link up with state run emissions equipment. These systems are best suited for racetrack use where engine tuners can fine-tune the program to the environment of the moment for optimal performance.
In a typical piggyback system, control over the engine is done by manipulating inputs to the stock PCM. Manifold air pressure and oxygen sensor voltages can be altered in order to make the PCM change its load calibration, thus altering fuel and ignition advance curves. Reducing MAP sensor voltage has the effect of reducing injector pulse width by making the PCM “think” the engine is under greater vacuum than actual. At the same time, ignition timing is advanced due to the PCM believing the engine is under a lower load. Conversely, increasing voltage has the opposite effect, increasing fuel and reducing timing advance. When tuning with systems of this type, you can find yourself in situations where you can have proper part throttle tuning, or proper full throttle tuning, but rarely both if the engine is heavily modified or has forced induction.
The VEC3 offers the best of both worlds. Stand alone system control, but with the simplicity of a piggyback system. The VEC3 controls fuel and timing, leaving the stock PCM to handle all other functions, such as idle speed, A/C control, emissions operation, etc.
Sharpi
