ECU remapping is basically fine tuning the software program that controls your engine management system (ECU). Most reputable companies use bespoke maps that are tailored to your car and your own individual requirements.
Today's modern engines rely heavily on computer controlled engine management systems. Basically each engine has an array of sensors which monitor lots of things such as throttle position, crank position, airflow etc. These signals are sent to the Engine Control Unit (ECU), which processes the information received to give the best engine performance for any given driving condition.
So why should I remap my ECU?
When vehicles are distributed throughout the world, manufacturers adopt a one map fits all policy. This one map has to take into account many different factors that are necessary for each export country. Areas such as climate, emissions, fuel quality etc all have to be considered by the manufacturer. What this means is that a vehicle ECU is never optimised for one individual situation.
So how can a reputable ECU remapping company help?
They will actually read your own engine's map file, modify it and then upload it back to the ECU. The company should always take the time to find out your own individual requirements and what you want to achieve from a remap. They will then tailor the map to suit before it is uploaded back to the ECU. By remapping your ECU it is easily possible to release extra power and torque from your engine without any reliability issues. Many owners also report that they have seen improved fuel economy once their engine has been remapped (chipped). Be aware that although many customers experience improved fuel economy, this depends on your own driving style and how heavy your right foot is.
The increase in power and torque that is gained using ECU remapping provides a much smoother drive, with increased flexibility throughout the rev range, allowing for smoother acceleration and better overtaking.
Beware of cheap imitations...
There are many companies out there offering what seem like value for money ECU remapping services. Most of these companies use stock files (maps) that are cheaply available through the internet or other sources and are NOT tailored to your own individual requirements. These can actually damage your engine as they are not specific to your vehicle.
Before remapping your ECU any reputable company should carry out a full diagnostics check of your engine and advise you accordingly if there are any potential problems or components that need replacing. Please be aware that, although remapping/chipping an ECU does not cause failure it can exasperate already failing components. In order to assure a quality ECU remapping service the company of choice should not carry out work on any engine that is found to be faulty without written consent from the owner. If they ignore faults shown up by the diagnostic process, then make your excuses and politely leave their premises.
What kind of improvements can I expect?
As mentioned you will notice an improvement in power and torque right throughout the rev range, along with the possibility of improved fuel economy. See below for a general idea of average improvements for different engine types:
Petrol (non-turbo) By remapping a normally aspirated engine ECU, you would normally expect to see a 10 - 15% increase in power (bhp) depending on your exact engine specification, and around a 15 - 20% increase in torque (Nm) throughout the rev range. This improves engine response on a lighter throttle.
Petrol (turbo) By installing a modified engine ECU map on to a turbo engine you would normally expect to achieve around a 20 - 30% increase in power (bhp), with an increase in torque of around 20 - 40% depending on your engine specification. The large increases in both power and torque will greatly improve the engine flexibility in all gears and throughout the rev range.
Diesel (turbo) Remapping a diesel turbo ECU normally sees the greatest gains of any engine type. Typically you will achieve an increase of 25 - 50% power (bhp) and around a 50 - 75% increase in torque depending on your engine specification. The engine response is greatly improved throughout the whole rev range and in all gears. Diesel engines are well known for providing huge amounts of torque and in gear performance. A remapped modern turbo diesel engine has the ability to embarrass many petrol engine cars under normal driving conditions.