Car remapping: What is it, how it works and how it affects your insurance

Car remapping, also known as ECU tuning, involves optimising your car's engine software for improved perforamnce or fuel efficiency.

This guide will walk you through everything you need to know about remapping your car in the UK.

What is car remapping and how does it work?

Remapping a car is a method of improving the power, fuel effciency and performance of a vehicle. This involves a process whereby the Engine Control Unit (ECU) software is modified by reprogramming its settings.

The ECU is a small computer in your vehicle with its own factory settings that control the engine's functions.

Previously, an older method involved removing the existing ECU in a vehicle and replacing it with a new one. This was known as 'car chipping', but with advances in technology, you can now simply reprogram the existing ECU instead.

The process of remapping overwrites a vehicle's factory settings and can optimise:

• Fuel injection

• Turbo boost

• Engine response

• Ignition timing

Car remapping is completed in 3 stages involving reprogramming the ECU software and updating the vehicle's hardware:

Stage 1: The ECU software is reprogrammed from its factory settings and updated.

Stage 2: Some parts of the engine must be modified to function in accordance with the new ECU settings.

Stage 3: New parts are installed. To accommodate these changes, a custom remap is usually recommended and needs to be tested.

When cars are built by manufacturers, the ECU factory settings are often 'detuned'. There are a few reasons why, but typically it's done so that the vehicle's emissions are compliant across different markets.

What are the benefits of remapping a car?

Remapping your vehicle's ECU can improve various aspects of the engine's performance.

These changes can be implemented through reprogramming, but certain features can only be realised if certain hardware modifications are made. Car remapping benefits include:

• Increased horsepower and torque

• Improved fuel economy (especially for diesel cars)

• Enhanced throttle response and drivability

• Smoother power delivered

• Better towing capability

• Customisation to driving style

What are the risks and disadvantages of car remapping?

Remapping your vehicle's ECU can help unlock various performance capabilities. It can be a complicated process if you don't know how to reprogram an ECU, so it's worth at the very least consulting a qualified mechanic.

If the process isn't completed properly, it can create mechanical issues with your vehicle. Even if the work is carried out successfully, there are other implications to be aware of:

Voiding warranty: Remapping a vehicle's ECU generally voids the manufacturer warranty. At the very least it'll likely prevent you from accessing any engine repairs under the warranty. Each manufacturer warranty is different, so it's worth checking the terms and conditions.

Insurance invalidation: Insurance providers typically ask you if you have modified your vehicle in any way before offering a quote. When getting car insurance, you'll need to disclose any changes regarding a reprogrammed ECU. If you remap a vehicle during an existing car insurance policy, you must inform your insurer. Not doing so can invalidate your insurance.

Increased wear and tear: The clutch, gearbox and brakes can become accustomed to the factory settings of an ECU. Remapping a vehicle can help improve engine performance but can put additional strain on some of these components.

Reliability issues: The technical nature of reprogramming an ECU can create long-standing issues if not completed properly. A mishandled reprogram attempt or excessive remapping can result in mechanical problems such as engine failure.

Emissions implications: Each country has emissions standards. A 'detuned' vehicle with factory ECU settings ensures your car meets emissions standards regardless of country or region. If you reprogram these settings, your vehicle might not meet these emission standards.

Resale value: Vehicles that have been modified can make buyers and dealers think twice. They might perceive modifications as masking or attempting to fix issues with a vehicle. As a result, it can affect the resale value of a car.

Leasing contracts: If you lease a vehicle and you're considering remapping its ECU, you need to check first. The contract of your lease typically explains what changes you're entitled to make. Remapping your vehicle can violate the contract, so you'll need to establish whether you can change the settings of an ECU first.

How much does car remapping cost in the UK?

The cost of remapping your car largely depends on the model of your car, where you have the work completed, and how comprehensive the process is. For example, a stage 1 software-only remap can cost you in the region of £200 to £500.

Further remapping involving upgrading hardware, new engine parts and testing can cost up to £1,000 and beyond.

While costs vary, always be cautious of unusually cheap remapping quotes. We've highlighted the risks associated with faulty remapping not completed up to standard. That's why it's worth comparing quotes from IMI-approved garages or mechanics and those offering a warranty for the remapping to work.

Does remapping a car affect car insurance?

It's more than likely that remapping your car can affect your car insurance. That's because the process of reprogramming a vehicle's ECU is considered a modification.

Modifications that improve the performance of a vehicle can increase its value and risk profile. Because of this, your car insurance premiums could rise following the process.

If you're planning on remapping your car, you must tell your car insurance provider. Failing to do so can invalidate your policy, and any potential claim you make might be rejected. It's worth bearing in mind, as insurers sometimes use social media and other means to catch drivers for any undeclared modifications.

Some insurers might decide against offering cover for remapped vehicles. If you're struggling to find car insurance for a modified vehicle, it might be worth considering specialist insurers or brokers. Comparing car insurance quotes can help you bring down the cost of car insurance, so it's always worth shopping around.

Is remapping a car legal in the UK?

Yes, remapping your vehicle's ECU is legal in the UK. However, any changse you make must comply with road safety laws and any environmental regulations relating to emissions standards.

Remapping your car can also have MOT implications, but if it's completed professionally, it shouldn't result in a failed test. A DPF removal, sometimes linked to remapping, is illegal and will cause your vehicle to fail an MOT and can result in fines up to £1,000.

A qualified mechanic or reputable garage should be able to offer advice surrounding the legality of vehicle modifications, including car remapping. This can help ensure your car is compliant if you do decide to reprogram the ECU of your vehicle.

Can all cars be remapped?

No, remapping a vehicle's ECU isn't always possible. Typically, only vehicles manufactured since 2000 have the necessary technology to remap the ECU. If your vehicle is older than this, you might need to modify or replace the ECU entirely for remapping purposes.

Turbo and diesel engine cars are commonly remapped - these vehicles tend to benefit from the greatest improvement in performance. Other cars may not receive a noticeable enhancement from remapping, so it's worth weighing up the cost involved against the potential improvement.

If you're unsure, consult a professional about whether your vehicle is suitable for ECU reprogramming and what level of improvements you can expect.

How to tell if a used car has been remapped (and what to do)

The signs that indicate whether a car has been remapped aren't always obvious. In terms of visibility, look for:

• Suspiciously high performance

• Consistent engine management light

• Black soot from the exhaust

• Stickers indicating remapping

If you buy a used car, its vehicle service history could cite whether a car has been remapped, but ultimately it's your responsibility to find this out. If you can't establish whether the vehicle's ECU has been reprogrammed, you can ask a trusted garage to run diagnostics to find out.

Should you remap your car?

Whether you should consider remapping should depend on your vehicle and circumstances. It's important to weigh up all of the benefits remapping can offer against the associated risks of the process.

On one hand, you can improve your vehicle's performance and its fuel economy, unlocking the true potential of the engine. However, it can be costly and might affect your car insurance premiums. You also need to consider whether it can affect any warranty you have with the vehicle.

If the process isn't completed properly, it can cause engine failure and potentially create further issues. That's why it's important to spend time comparing quotes and garages to find a reputable, authorised mechanic to complete the remapping process.

If you do decide to remap your car, remember you must inform your insurer of the modification. It can invalidate your car insurance policy. This is an expensive mistake if a potential claim is rejected as a result.

There are other ways of improving the performance and fuel efficiency of your car if you decide against remapping its ECU. You can also consider:

• Replacing the vehicle's air and oil filters regularly

• Maintaining your car with an annual service

• Upgrading your tyres

• Reducing the weight of your vehicle with a clear-out

• Inspect your spark plugs and change them if necessary