Choosing a Diesel Tuning Chip or Diesel Tuning Box

If you read car tuning magazines, browse on-line forums or talk to other car enthusiasts and mention diesel tuning boxes or diesel tuning chips (ECU remaps), you will often find that people have very different opinions.

Some people will categorically state that a diesel tuning box can never provide the same performance enhancement as a diesel tuning chip or ECU remap. Others will say that both options will damage the engine, while some enthusiasts will promote the particular brand of diesel tuning box they have installed.

To be clear, we are talking about the more expensive diesel tuning box options which provide a complete tuning map, and not those that simply ‘fool’ the engine into thinking it’s colder than it really is and supplying a richer fuel mix. While we only sell diesel tuning boxes, we thought it would be useful to list the similarities and differences between external diesel tuning boxes and diesel tuning chips or ECU remaps.


A diesel tuning box can be installed by anyone with basic skills. The Speedhawk tuning box only need a single cable to be attached to car, although some other makes need additional wiring. You do need to find a sensible location for the tuning box to be mounted in the engine bay – most are around the size of a deck of cards up to around twice that size. They need to be mounted in a location away from significant heat, water or electrical interference.

Diesel Tuning Chips or ECU Remaps generally have to be carried out by a specialist in a workshop, although mobile services also exist. As they are usually altering the programming of the existing ECU chip, they take no additional space in the engine and no consideration needs to be given to location or wiring. ECU remaps require the chip to be replaced, which is normally a specialist operation.


A properly fitted diesel tuning box and a remapped diesel chip will provide very similar performance gains. There are some variations between different suppliers depending on how far the engine is tuned. Even cars of the same make and model can achieve different results, depending on the condition of the engine.

Diesel tuning boxes will come with one or more pre-installed tuning maps (the Speedhawk Common Rail box has 10). These must be specifically for the engine they will be installed on to. One advantage to diesel tuning boxes is the ability to switch between the multiple maps without returning to the workshop.

Diesel Chips Tuning will generally only allow a single new tuning map to be installed. This will generally be a tuning map designed for your make and model of car. Some of the more expensive tuning services will test your vehicle on a rolling road to check and further adjust the tuning map. This has to be done in a full workshop with dyno facilities. If you need to make changes to the tuning map, this will need to be done in the workshop.

Servicing and Warranties

While most independent garages will have no issues, many main dealers will not work on vehicles with modifications
It would be obvious to the mechanic that a diesel tuning box had been fitted, as the box and wiring are visible. Diesel tuning boxes can be quickly removed at home to revert the vehicle to standard before putting the car in for a service, and then re-installed afterwards.

It is not instantly obvious that a ECU remap has been applied, and if it is not relevant to the work, it may well not be noticed. However, most engine diagnostic systems will identify the remap. Reverting the vehicle to standard will mean a trip to the tuning workshop before it goes in for servicing. Some manufacturers will automatically wipe any non-standard tuning maps when a vehicle goes in for servicing, forcing you to pay to get it re-installed.

Selling a vehicle

Diesel tuning boxes can be easily removed. It is often possible to move the tuning box to a new vehicle, providing it uses the same technology (common rail or pumpe duse). The diesel tuning box will probably need new maps installed. New maps can be added by the supplier, or at home if the tuning box has a computer connection, and you have suitable software. A different connecting cable may be required, as different manufacturers use different connectors.

Diesel tuning chips will have to be sold with the vehicle. If you wish to sell the vehicle as ‘standard’ it will need to be taken to the workshop to have the tuning removed. Your new vehicle will have to have a new ECU Remap added separately.

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