ECU remapping is a long and complex topic – however, I will try to keep things as simple as possible for now. Many of these questions can be answered in our why dyno section – http://eccustoms.wpengine.com/dyno-tuning/
To begin, when a manufacturer develops a map for an engine or vehicle, they build into it an extremely large margin of error to cope with a wide variety of conditions, as well as levels of user error and / or neglect. The bottom line – manufacturers do not want people breaking down, suffering premature parts failures, or a reputation for uneconomical or unreliable cars.
In combination with this, each and every car that leaves the production line is different – some make less lesser numbers, some exceed manufacturer specifications, some last forever, others don’t survive their first few months on the road. The reasons for these changes are so varied and a whole new discussion for another time – but what must be remembered here is that as part of the manufacturing process, all vehicles of the same make and model receive the same ‘generic map’ – a map that has been developed with a ‘one size fits all’ philosophy, which means that from the day the car rolls off the production line, there are improvements to be made simply by tuning the vehicle on its merits.
Believe it or not, manufacturers quite often use nothing more than a few of the most basic map changes to differ power levels from entry to higher performance models – I could list a few very well known ones here, but shall choose anonymity for now.
ECU remapping is when we use this generic map that the manufacturer has provided us, and improve on it in the areas where the specific vehicle can gain some benefit. This usually comes in the way of optimizing ignition timing, fuelling, throttle body control, transmission control, and torque management strategies. This does not add any extra unreliability into the equation, as all changes are carefully measured and programmed specifically for each vehicle – in a lot of cases, these remaps can ADD reliability to your vehicle.