You already know how remapping the ECU can improve your car’s performance: more power and torque, smoother handling, better fuel economy. Now all you have to do is find someone to do the work. You’ll probably notice that some companies advertise custom or bespoke maps and other companies talk about using library maps. It’s really important to know the difference between the two types of remapping. Bespoke remapping can be more expensive, but it has significant advantages that make it well worth the cost.

Bespoke or custom remapping begins with the file that is in your car’s ECU right now. The technician downloads the original ECU map from the car and then modifies parts of it to enhance engine performance. The files for many different processes are tuned with expensive computer software. The technician must understand the best way to recalibrate each setting — in other words, he has to know what he’s doing.

In addition to the maps that control fuel combustion, the ECU also contains data pertinent to your vehicle such as immobiliser information, software updates, bug fixes from the manufacturer, and so on. For this reason, only the files that need to be changed are touched during the remapping — other vital data about the car is left intact. Then the map is flashed back to the ECU, overwriting the existing file. A copy of the original ECU file is kept by the service provider, just in case. Bespoke remapping is always tailored to your particular vehicle, which ensures the best possible results.

Remapping with a library file is quite different. The technician doesn’t use the original ECU file from your car. Instead, a modified ECU map is chosen from a library of perhaps 10,000 generic files. The library file is copied back to the car’s ECU, overwriting everything — including any vehicle-specific information that might have been on the original file.

Now, this collection of library files has a shady past. It consists of ECU files that someone compiled from unknown sources, copied to a CD, and sold for a few pounds over the Internet. Many, if not most, of the ECU files were stolen from professional remappers. As a result, you really don’t know anything about the quality of the files or how they might affect your engine.

Remapping the ECU with a library file is a mistake that can have dire consequences. The library file probably won’t contain the immobiliser software that keeps your vehicle secure. It won’t have recent software updates or crucial bug fixes. And let’s not forget that a service provider using library files probably cuts corners in other ways, with cheap tools and minimal technician training.

What happens when you replace a vehicle’s unique ECU map with a library file? Certainly the engine might output more power after the remap, but there is no guarantee that the improvement will be what you expected. Your engine system may suddenly develop glitches and fail to operate as it should. The ECU could freeze up and become inaccessible so you can’t even fix the damage. Without the normal security features, your car could be stolen more easily. And worst of all, you might be forced to spend a lot of money replacing the ECU or repairing the engine.

Now that you know why custom maps are so much better than library maps, how do you find someone to do the work? First and foremost, make sure the company really does offer bespoke remapping that is performed by qualified technicians. It’s not hard to tell whether you’re dealing with a professional or a poseur. Just ask the technician a few questions about how the remapping is done, what type of files he uses, which engine settings are changed, and so on. A qualified and experienced individual will be perfectly able to explain the finer points of the remapping process to you. And if someone mentions library files or tries to convince you that library files are just as good as custom files, cross them off the list.

There’s nothing wrong with shopping around to compare prices, but don’t make price the deciding factor. This is a high-tech industry and technology costs money. If you find a service provider with very low prices, ask yourself why. In all likelihood, they are using library files and cheap tools for remapping.

You should also reassure yourself about the company’s after-sales support. Is there a trial period after the remapping? Do they keep a copy of the original map in case you ever want to change back? Does the workmanship come with a warranty? Does the company guarantee improvements in BHP, torque, and fuel economy? Make sure you’re happy with the answers to these questions

Remapping the ECU is an effective way to boost engine performance, but if it’s not done properly you really do put your car at risk. There’s no question that bespoke or custom remapping is a better option than remapping with library files. You’ll get the best results, and equally important, you’ll protect your expensive vehicle from damage.