GNRS ECU Remapping

At GNRS, your vehicle remap will be done by qualified technicians certified and approved by the IMI (Institute of the Motor Industry). GNRS Remapping has a partnership with a UK-based global brand, who are a market leader in the remapping industry, that offers access to software solutions for over a range of 6000 cars, vans, motorhomes, truck and tractors. Each vehicle / software is reprogrammed on the rolling road to give the best power / fuel economy settings, thus ensuring reliable and robust data packs. This data is then reprogrammed into a customer’s vehicle (ECU Programming).

What Exactly is Engine Remapping?

No hardware is added or changed during the remapping process; it is solely a software adjustment where the operating parameters are modified to produce better results, i.e. maximize the performance of the vehicle and even sometimes improve on fuel economy.
To adjust parameters, such as fuel pressure, boost pressure, ignition advance and throttle pedal control, the car's ‘map’ stored in the ECU’s processor is accessed in two ways:
(i) via the on-board diagnostics port (OBD) in the vehicle, or,
(ii) the ECU is located and physically removed from the vehicle, programmed and then restored into its original location.
Once the remap is complete, you will experience better and improved driveability, stronger performance in your vehicle, shorter journey times, stronger acceleration, 10-35% extra power and better fuel economy – who could ask for more?

So, What is Chip Tuning?

This is just like remapping; the process differs only because the program chip is physically removed from the ECU in the vehicle and either re-programmed or replaced with a new chip. Technology has advanced in newer vehicles making this procedure more uncommon; however, this is still the only way to remap certain vehicles.

What Tuning / Remapping Options Can We Offer You?

Green (Turbo Diesels Only) - Designed to return an improved economy in turbo diesel engines. By recharacterizing the torque limits on the engine, at lower RPMs you will benefit from additional performance and improved economy. At higher RPMs the software will encourage shifting up through the gearbox, to keep the engine running in its optimal window. Generally, a very popular choice with large fleet owners, where the extra mpg improvement counts on the bottom line profit.

Blue (Turbo Diesels Only) - The most popular remap choice, offering the best mix of power and economy in virtually all turbo diesel engines. Designed to de-restrict the engine and open up the true torque and power range. Blue offers a better driving experience while returning an improved fuel consumption figure. Parameters are carefully managed to optimize best burn times and achieve optimum in cylinder pressures.

Red (Petrol & Diesel) - Designed to fully unleash the full potential of your engine. Ideally used in situations where the extra power and torque is required for example moving extra heavy loads, running optimized acceleration, experiencing a wider torque window, or simply to enjoy your vehicle.

Other Tuning Options

EGR or DPF Software Switch off option, or Speed Limiter Removal Option, or Rear Lambda Sensor (Petrol Only) Switch Off option free of charge with above remap (dependent on vehicle).

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DPF (Diesel Particulate Filter) Solution

Customers may require a software DPF deletion when remapping a vehicle, each case is different and treated accordingly. It is not recommended for road use and inspection of the exhaust system carried out during the M.O.T test will include a check for the presence of a DPF.

What is a DPF?

A DPF (Diesel Particulate Filter), FAP on some French vehicles, is a device fitted to the exhaust system of modern diesel vehicles to reduce emissions and to meet emission standards. It does this by trapping soot from the exhaust gases whilst permitting flow of the gases through the system.
As like any type of filter a Particulate Filter needs to be cleaned regularly to function properly. With DPF's this is done by a process known as Regeneration which involves a combination of a catalyst function in the system and burning the soot to gas at a very high temperature leaving behind an ash like residue within the DPF. Regeneration should be an automatic process taking place in the normal use of your vehicle, you may have noticed this in the form of a blast of white smoke from the exhaust on occassions. When regeneration is taking place you will notice a reduction in fuel economy.
DPF's have been in common use in passenger cars and light commercials from around 2003 in preparation for Euro 4 regs(2005), with Peugeot, Renault and BMW being early takers. Euro 5(2009) made it compulsory for diesel cars and light commercials to have a DPF fitted and Euro 6(2014) has tighten this up further.

When is a DPF Solution Required?

  • DPF error
  • DPF or Limp Home warning lights on your dash
  • Poor acceleration and fuel economy
  • DPF too expensive to replace
  • vehicle no longer requires DPF (off road use)


M.O.T will check for a visual presence of a DPF from February 2014, a missing DPF will result in a M.O.T failure.
A vehicle might still pass the M.O.T visible smoke emissions test, which is primarily intended to identify vehicles that are in a very poor state of repair, whist emitting illegal and harmful levels of fine exhaust particulate. It is an offence under the Road Vehicles (Construction and Use) Regulations Act (Regulation 61a(3)) to use a vehicle which has been modified in such a way that it no longer complies with the air pollutant emissions standards it was designed to meet.
Removal of a DPF will almost invariably contravene these requirements, making the vehicle illegal for road use. The potential penalties for failing to comply are fines of up to £1,000 for a car or £2,500 for a light goods vehicle.

Problems Encountered with DPF

If regeneration doesn't function properly it leads to a build-up of soot affecting vehicle performance and fuel economy. If left unattended this will result in a blocked DPF which can ultimately cause very expensive damages to other engine components. A blocked DPF is also potentially dangerous as it can cause overheating in the exhaust system and cause a fire risk. To prevent this damage most new vehicles will go into 'Limp Home' safety mode at this stage, meaning the vehicle will have minimum power - barely sufficient to crawl home.
For regeneration to take place it requires the vehicle to be driven regularly at some speed on open roads, e.g. motorway driving, typically driving at around 2500RPM for approx. 15-30mins at least once a month, this will help keep things working.
Many diesel vehicles are used primarily in urban areas or on short stop start journeys, e.g. local deliveries, taxis, school runs, etc. and many have auto gearbox, so the vehicle does not get the chance to heat up sufficiently and is unable to carry out a full regeneration process.
Even if the regeneration functions as it should, over time the ash like residue will build up in the DPF and have same affect ultimately resulting in a blocked DPF. For this reason, a DPF is classified as a serviceable item by the vehicle manufacturers, just like brake pads or air filters etc. and not covered under warranty. DPF Systems therefore need to be maintained properly.

What Are My Options?

If the vehicle DPF warning light is on your DPF will already be significantly blocked. Forced regeneration by a garage or a "blast down the motorway" is not likely to cure the problem; these only work as preventative maintenance. So at this stage realistically you have the following options:

  • DPF Regeneration - we can offer a regeneration service
  • DPF Replacement - we offer a replacement service dependant on vehicle, please contact us
  • DPF Cleaning - we offer a DPF cleaning service dependant on vehicle, please contact us
  • DPF Recalibration - if you have had your DPF core removed, we may be able to recalibrate your vehicles ECU to stop your engine going into limp-home mode and clear the DPF warning light. Consumers must be aware of the legal implications (as above) of this being carried out.
DPF Removal is legal in certain countries and when used for off-road or motorsport. If any any doubt, please take advice.

EGR (Exhaust Gases Recirculation) Solution

Customers may require software EGR deletion when remapping a vehicle. Each case is different and handled accordingly.

What is EGR?

An EGR valve is switched on/off via the ECU under certain conditions to reduce NOx emissions. The valve allows exhaust gases to recirculate back into the engine via an engine air inlet. The valve can usually control the flow of gas, by having the valve fully open to fully closed.


Why is an EGR Needed?

Exhaust recirculation adds burnt gases into the combustion chamber, reducing the oxygen content present in the air within the chamber. The combustion process now burns at a lower heat release and peak cylinder temperature which results in a reduction in the formation of NOx. The presence of a inert gas in the cylinder further limits the peak temperature.

Diesel Engines - As diesel exhaust gases contain soot particles, when the EGR valve recirculates this gas, the soot can eventually make the actual EGR valve clog and fail, other valves and flaps can fail too (throttle valve, swirl flaps, turbo charger vanes); leading to a costly bill. Newer engines have an EGR cooler built-in, which results in even faster clogging.

Clogged throttle flap, sometimes throttle flaps have tiny holes for airflow, any clogging of these holes can usually produce poor idling issues. Clogged/Blocked EGR valve, will cause poor engine running and eventually the dashboard engine warning light will turn on. Clogged swirl flaps in the inlet manifold will cause poor fuel economy and reduced max power/torque. Clogged Variable Vane Turbocharger will cause reduced max power/torque & engine response leading to limp home mode warning light. Clogged or soot coated engine sensors will lead to false readings sent back to the ECU (Engine's Brain), leading to poor emissions, fuel economy, reduced max power/torque & engine response.

All the above can be eliminated by switching off the EGR circuit when remapping your vehicle. An EGR valve may give optimum emissions when the vehicle is brand new, but as the miles are put onto the vehicle the above pictures clearly show the benefit is of a limited time period. A switched off EGR valve will run better than any of the above scenarios as it will prevent clogging and soot build up, and finally added cost of repairing/replacing parts.

Petrol Engines - As petrol engines use EGR valves to aid fuel economy at partial throttle to prevent pumping loses, due to this we do not advice customers to change setting on Petrol Engine EGR valves. Should the valves become clogged, we recommend to unclog the vavle or fit a new one, but never switch the valve off as your will experience reduced fuel economy. As future EGR systems evovle using low pressure, cooled and even fast acting EGR systems fuel economy will further improve up to 5%.

EGR Solution

GNRS offer a solution for Diesel EGR Valves only. The valves can become clogged with Carbon desposits, causing them to fail or stick, thereby producing error codes and affecting the vehicle by not running correctly. Our software solution is to disable the EGR valve in a simple and effective method of improving the efficiency of your engine and to avoid costly bills to fix clogged or failed valves and swirl flaps. EGR valve disabled does not reduce fuel economy once the engine reaches optimum temperatures.

What are the Benefits?

  • As mentioned above, to prevent clogging and failure of parts, which may lead to engine failure and further expenses.
  • Removal of the EGR system by Blanking off the exhaust input and reprogramming of the engine management ECU results in lowered engine temperatures, improved throttle response, economy and also can lengthen engine life by reducing oil contamination and carbon deposits.
  • We only advice EGR switch off on Diesel engines only

EGR Configurations

In this section we aim to provide an understanding that remapping and the engine as a whole is a sub-system on how to improve fuel economy. The vehicle can be looked on as a tool on how to achieve better fuel economy. Tips below:

  1. Remapping a vehicle can improve fuel economy. Mapping at light throttle yields better results and improved fuel economy in comparison to the manufacturers standard mapping.
  2. Fuel Injector cleaning helps maintain spray patterns within the combustion engine. It aids correct fuel atomisation maintaining fuel economy, power and torque. Our Special offer page is giving away a free bottle of Injector cleaner with every remap.
  3. The condition of your tyres can greatly affect fuel economy: tyre pressure should be correct; under inflated tyres reduce fuel economy. Using low rolling resistance tyres will further improve fuel economy.
  4. Incorrect wheel alignment will cause additional frictional drag between the tyres and road surface. You would be well advised to check and adjust wheel alignment at the correct intervals.
  5. Driving a vehicle in a high gear, at low RPM, with light throttle applications and using cruise control at motorway speeds really helps with improving fuel economy, as it prevents unwanted acceleration and deceleration; (use cruise control when it is safe to do so).
  6. It is economical to switch off the air conditioning when not needed. When the vehicle requires cooling, you may instead, open windows while driving at low speeds, or, use air conditioning at high vehicle speeds, remembering to turn it off once optimal temperatures are reached.
  7. Additional weight within the vehicle will reduce fuel economy. Lighten your load. by removing additional weight which is not required: e.g, remove roof rack, excess items stored in boot, etc.
  8. Remembering to service your vehicle at the correct intervals, ensuring service checks of the oil, oil filter, fuel filter, spark plugs (petrol only), all improves the life of your vehicle in addition to economizing on fuel. The use of synthetic oils maximizes engine protection and aids in better fuel consumption.
  9. Vehicle aerodynamics - avoid using roof racks. Make sure underbody trays and ducts are in good condition and attached to the vehicle correctly. Ensure windows are closed when driving at high speeds.
  10. Check engine sensors with Vehicle Technician's diagnostic equipment; any failed or failing sensors will reduce fuel economy. Request your Vehicle Technician to go one step further and examine any sensors which are working within tolerance conditions, and are appearing to fail: replacing them will aid fuel economy. For example, MAF (Mass Air Flow) and/or oxygen sensors all go out of calibration with use and age of vehicle, as the sensor goes slightly out of calibration fuel economy usually suffers. As part of our remapping service, GNRS offer a free diagnostic check before any remapping.

Vehicle Assessment

As part of our remapping package we offer a free engine diagnostics check before any remapping. We pick up on ECU error codes and discuss them outright with the customer. If there are potential engine issues that deem the vehicle does not qualify for a remap, we are honest and advise accordingly. We will also notify you if sensors need changing. We never overstate statistics and make projected data to look better than the actual outcome of a remap.

Accurate Remapping Data

All our Remaps are performed on a Rolling Road on an identical Vehicle. The data is then transferred into the customers vehicle during the remapping process. Rolling Roads ensure high quality remapping, safeguarding a stable platform to provide precise mapping, which in turn aids power and fuel economy gains: it protects the engine by way of operation checks of engine data inputs using internal and additional sensors. Ultimately, we provide a Remap which will never damage an engine - beware of tuners who do not remap via rolling roads as engine damage would be probable.

Safe & Approved

All our remapping operations are carried out by fully qualified professionals, certified by the IMI. You can rest assured that your vehicle is in safe hands when it is with GNRS, and that work being carried out on it is being done by those with the necessary knowledge, skill and experience backed up with the right qualifications.

Established Equipment

The equipment used for remapping is verified and well proven AlienTech KTAG & KESS V2. High quality and sustainable tools ensure safe, robust remapping operations.
Any Electrical Power cuts while remapping will cause ECU (Engine Control Unit) failure, we have backup measures in place to ensure maximum protection: if a Power cut were to happen, the remapping process will continue as intended through use of Uninterruptible Power Supply (UPS) + Linear Main Power Supply to provide stable & clean voltages. It is extremely important to use these power supplies for safeguarding the ECU.


GNRS have been working with the internal combustion engine since 1987, and aside from remapping, we provide an engine consultancy and machining service. Therefore, we genuinely know our "stuff" when it comes to understanding the operations of an engine. Should you have any further questions, please contact us.

Customer Satisfaction

At GNRS we aim to maintain a high level of customer services by providing high quality workmanship, delivered at the right time. We offer convenience with the remapping facility: Customers can drop off their vehicles at our facility, or alternatively, opt to have a technician travel to them (additional charges will incur). Lastly, if you are not happy with the performance or results of the remap you have a 30 day money back guarantee.


 Find My Vehicle

Frequently Asked Questions

Car companies around the world must sought after a general formula (which incorporates a large variety of safety factors), that works well in mass production in the manufacturing industry as cars will have different destinations world wide after assembly. That is why air-fuel ratios are more conservative: remapping allows the ratios to be optimized (See Remapping tab for better understanding).
MORE... Original Equipment Manufacturers (OEM) have to put high safety margins into the remapping strategy, mainly due to the poor quality of fuel that is available in parts of the world. Western Europe is fortunate to have good quality fuels and stable ambient temperatures, i.e. the U.K. is not extremely cold like for e.g. Canadian winters which can reach -40°C; or, e.g. Dubai summers can easily reach 45°C.
Some of the OEM's Engine Dyno tests (engine test bed), which have been carried out are too extreme and the end customer will, on no occasion, experience these extremities in a vehicle. A vehicle has excessive built in cooling systems in place, whereas, on the engine, cooling is only provided by fans with no duting; sometimes the fans are not directed to the correct areas leading to excessive heat build up. Taking this into consideration, we can reduce the safety margin but not eliminate the safety factor.
Example test - An engine is tested rigourously at maximum RPM for 300 hours uninterrupted. When driving a vehicle, this is unachieveable because any max RPM is more transient rather than continous: we would hit max RPM at maximum acceleration and then change into a higher gear. 1st Gear Max RPM (30mph and above), would provide more ambient cooling flow than most dynos, plus dynos do not duct air to the correct areas, whereas a vehicle bumper and integrated ducting is designed to force air into the correct areas, i.e. to the radiator, turbo, intercoolers, oil cooler, engine block and cylinder head.
Usually the vehicle will be left with GNRS for ½ a working day, unless otherwise advised prior or during the servicing.
Remapping will not cause a MOT failure. If a MOT has failed we recommend the vehicle ECU to be connected to diagnostics equipment; the likely cause would be a sensor about to fail or one that is out of calibration. Let the diagnostics engineer guide you to the likely cause.
Part of the engine remapping process is to clear the Engine Codes, if any codes have been detected we inform the customer accordingly, so they know if anything needs to be replaced or checked.
We can give you precise details on what remapping will do to your vehicle, you may contact us, and giving us details as your vehicles make, model, year of manufacture, including your registration. Alternatively, please click on "find my vehicle" for exact power improvements, here.
There are many benefits to an ECU remap / chip upgrade:
  • Improved MPG during everyday normal driving, helping to reduce fuel bills and your carbon footprint.
  • Improved throttle response
  • Increased power and torque
  • Experiencing smoother power delivery, removing flat-spots where possible
One important aspect we do not discuss readily as it is difficult to calcuate is engine transient improvement: smoother power delivery and safer overtaking; when the throttle is kicked down after a remap, one will feel far better instant throttle results.
Using better fuels can also help further, e.g. for petrol vehicles, using super unleaded can help increase power with its high octance rating, as the engine recognizes this fuel via its sensors, it can optimise the fuelling and ignition timing to provide more torque and power.
GNRS offers a 30 day money back guarantee, or the original map can be re-installed for example when the customer wants to sell the vehicle at a later stage.
  1. Click on Find My Vehicle to confirm power gains.
  2. When the vehicle is remapped the customer can test drive the vehicle to confirm difference.
  3. GNRS offer a 30 Day Money back guarantee.
GNRS offer a 30 day money back gaurantee. Within 30 days after remap, should you still not be satisfied, we restore the vehicle to its original map.
Fuel economy is a complex system, the engine and remap is a sub-system to the vehicle. For further information please see the fuel economy tab and real scenario case study. Overall we suggest for improved fuel economy:
  • Engine Remap - Blue or Green Option improve fuel economy: Mapping at light throttle as opposed to a vehicles standard manufactured map, will facilitate fuel economy, however, the following must be verified as well:
    • Fuel injectors spray - these aid to maintain a spray pattern within the combustion engine, supports correct fuel atomisation, sustaining fuel economy, power and torque.
    • Wheel alignment - incorrect wheel alignment will cause additional frictional drag between the tyres and road surface. Regular checks and adjustments to wheel alignment at correct intervals. If toe in toe out the customer will suffer excessive fuel consumption especially during town driving.
    • Tyre pressures - under inflated tyres increase fuel consumption. Low rolling resistance tyres will improve fuel economy further.
    • Air conditioning - should be switched off when not needed. Using natural ventilation (driving with windows down) at low speeds aids in cooling the vehicle down and saving fuel.
  • Initially, after your vehicle's remap you will tend to drive in a different pattern to your normal/typical driving pattern; which may result in reduced fuel economy (enthusiastic driving), or maintain same economy as original. Once your driving pattern returns to 'normal' it will then be easier to observe the changes in fuel economy as compared to the original map.