This article was adapted for drivers and tuning professionals in the United States by Viezu USA. Measurements are shown in US units alongside the originals.
What is a remap file?
A remap file is a piece of software holding an ECU's control map, which sets how the ECU for an engine, generator or transmission behaves in different situations.
It goes by plenty of names, including mod file, car map, chip tuning file, tuning file and engine remapping file.
How do you upload a remap file?
You need a tuning tool such as Autotuner or Magic Motorsport FLEX. It connects to the vehicle's OBD socket to read and write its files, or you can connect straight to the ECU, either through the ECU's own connectors (BENCH) or directly to specific points on the ECU circuit board (BOOT).
What does a remap actually do?
Uploading a remap file to the car's ECU modifies or replaces the manufacturer's settings. You download the original ECU file, change it, then upload the new version back to the ECU.
How is a car remapped?
Remapping takes a tuning specialist who understands the engine control unit (ECU), how to adjust its parameters and how to program the changes without damaging it. If you're in the tuning trade, Viezu's professional file writing service has an experienced team of file writers who can safely make every change you need to the file.
How can I get my car remapped?
- The best option is to take your car to a professional tuner. Make sure they have:
- A good reputation (read Viezu's reviews)
- Plenty of tuning experience
- You can also remap your car with a personal tuning device. Our range of professional tuning devices includes brands such as:
These devices offer switchable tunes made specifically for your vehicle, using files written by a professional tuner.
- A third option is an under-hood tuning device such as the JB4 box, or in some cases a pedal box that changes your vehicle's throttle response.
What do you need to remap an ECU?
To remap a car, you'll need:
A laptop. Windows or Mac both work. The best laptops for car tuning offer:
- Good battery life, so you can move around without recharging
- Light weight, so it's easy to carry
- A powerful processor to load and run demanding remap software
- Plenty of SSD storage for saving remap files
- Several USB ports for connecting tuning devices
A tuning device or cable linking the car's diagnostic port to the laptop.
Tuning software, if you're a master tuner. Slave tuners don't need it; they send the file to their tool master, who does the editing.
A battery stabilizer.
Generic vs custom remaps: what's the difference?
Generic Remap
A generic remap is a file written for one vehicle that can be transferred to others with the same engine and electronics. It works across a set range of conditions, within safe parameters, and will have been customized and tested for its intended car.
Custom Remap
A custom remap is written by an experienced tuner to suit your particular vehicle, driving conditions, modifications or requirements.
An experienced tuner uses a rolling road dyno to get the most performance possible within safe limits. It can produce a dyno printout showing before and after figures for power, emissions, torque and other parameters.
How do you know if a remap file is good?
A good remap file delivers the positive results you set out to achieve with your tune.
What are the benefits of a good remap?
- More power: more horsepower available from your engine
- More torque: fewer gear changes, for a smoother drive and better acceleration
- Fuel efficiency: a by-product of changing gear less often
What makes a bad remap?
Whether a remap counts as "bad" depends on the goals and results you set.
For example:
- If the aim was more performance but the car is slow and sluggish afterward, that can point to a bad remap.
- Sometimes the aim of a remap is to limit performance, and Viezu offers tunes similar to a valet mode that do exactly that.
A remap can deliberately increase fuel consumption, but that's not usually the goal. So poor fuel economy, where more fuel is used because the vehicle's operating system is out of balance, can show that the remap hasn't done its job.
- A bad remap isn't always obvious at first glance, unless the ECU shows visible physical damage from water or being dropped, or the tuner overloaded a circuit or damaged the casing while connecting the vehicle.
- A bad remap is more likely to show up once the car is being driven:
For example:
- If components have been pushed past their mechanical limits, or the vehicle has been badly programmed, engine timing problems can follow.
- A damaged ECU can stop the car from starting.
- A bad remap can seriously damage pistons, cylinders, turbos, DPFs, cats and more.
Frequently Asked Questions
Can you tell whether a car has been remapped?
The most reliable way is to plug a laptop or diagnostic tool into the car's OBD (on-board diagnostics) port and compare the ECU settings with the manufacturer's defaults to see whether anything has changed. Unusual errors can also suggest modifications have been made.
How can Viezu help with remap files?
Viezu has the largest custom car tuning files support team, available 7 days a week. Remap files are custom written by experienced in-house tuning engineers to match exactly what you want from your tune.
With fast turnaround and an easy pay-as-you-go service, find out more and order your tuning files today. Order tuning files
US emissions compliance note
In the United States, modifying, removing or disabling emissions-control equipment (including DPF*, EGR*, SCR*/DEF* and catalytic converter systems) on a vehicle used on public roads may violate the federal Clean Air Act and EPA rules, and in California and other states that follow CARB standards, additional restrictions apply. Any off-road, race or competition-only modification described here is not intended for street use. Nothing in this article claims that any product or calibration is EPA- or CARB-certified or street legal. For guidance on options for your vehicle, contact Viezu USA.
Talk to Viezu USA
Want to know what Viezu can do for your vehicle or your business? Request a performance upgrade quote, browse viezuusa.com or contact the Viezu USA team.
* EMISSIONS TAMPERING WARNING
Removing, disabling, deleting, or rendering inoperative any emissions control device or system (including DPF, EGR, SCR/DEF, catalytic converters, and related sensors or software) on a vehicle used on public roads is prohibited under the U.S. Clean Air Act and may also violate state laws, including California Air Resources Board (CARB) regulations. Violations can carry substantial civil penalties for vehicle owners, installers, and sellers.
Any reference in this article to DPF, EGR, SCR, or other emissions-related functions is provided for informational purposes and, where applicable, for closed-course competition or off-road use only where permitted by law. Viezu USA does not condone emissions tampering on any road-going vehicle. It is the customer's sole responsibility to ensure that any modification complies with all applicable federal, state, and local laws, regulations, and policies, regardless of what country you live in.