To a degree, the plug in box is no different to the ‘one size fits all’ philosophy from the manufacturer. Where these are fraught with danger however is two fold. Firstly, attempting to increase vehicle performance through engine management tuning, no two cars should ever have a blanket philosophy to tuning thrown at them – the manufacturer can get away with it to an extent, being that their intentions are rather different from the “plug in box” manufacturer (reliability vs performance). Too many times we have seen on the dyno a “plug in tune” that has been loaded into a vehicle, and the mapping so horrifically wrong that severe engine damage had the potential to occur if not caught earlier. Just because a certain tweak to mapping will provide a safe performance increase for one vehicle, doesn’t mean it will behave the same in another – hence why we suggest custom tuning for your vehicle – the ability to tune YOUR vehicle.
Secondly, the methods in which some of the “plug in” boxes go about making their desired changes are often crude at best. They generally have a tendency to try and “fool” the ecu into changing certain parameters in an attempt to increase performance – for example, some units simply “bend” or manipulate the measured air flow signals coming into the engine, fooling the ecu into believing more air has been consumed, and hence delivering more fuel. Whilst at times this may give the desired result of “more fuel”, it is most certainly not the correct way to achieve this, and in turn can have dire consequences for all other systems in the vehicle that are also dependent upon the measured (often falsely) conditions.