What happens if I remove the EGR from my diesel car?

All diesel cars and many petrol cars have the EGR valve, a system that ensures part of the engine’s combustion gases return to the circuit and are used again in place of the fresh outside air. This helps the diesel engine deliver better performance at low revs and produce greater power when driven at low speeds.

The very operation of the EGR valve means that it closes when the engine reaches a higher rev range and then stops diverting those combustion gases to the engine. In these cases, the engine uses only fresh outside air and not the air that comes through the EGR.

Removing the EGR valve

Some owners decide to remove the EGR valve, thereby preventing the gas resulting from previous combustion from reaching the engine. Is this action positive or negative for the car? We find that there are several advantages to removing the EGR valve, but also disadvantages that can affect the normal running of the car, so let us look at both scenarios.

Pros of removing the EGR

By removing the EGR valve and preventing the recirculation of combustion gas, the deposits that can build up in the cylinders are reduced and the engine runs cleaner. Polluting gases also create a layer of residue at the gas intake to the engine, which leads to more deposits that can cause problems in the engine.

In addition, there is a certain fuel saving and an improvement in the car’s performance at low revs. Power and throttle response also improve in driving conditions with low and medium revs. These could be the reasons why someone might decide to remove the EGR valve, but there are also arguments against doing so.

Cons of removing the EGR

By removing the EGR valve, it does not operate when the car is driven at low revs, which is the most common mode of use in everyday driving. This means that emissions in this range of use will increase and may become excessive and be detected at the MOT. As a result, the inspection may be unfavourable and the car may fail.

The engine will also not run correctly at low revs, since it is designed to do so with some of those burnt gases and will not do so normally. You may notice noises and a certain roughness when it runs at low revs. And of course, fuel consumption will also increase, since the engine takes longer to reach its optimum operating temperature.

In reality, removing the EGR valve is not a good idea, since diesel engines are designed to use some of those burnt gases to run correctly. Any modification can have negative consequences for the vehicle and stop it from working properly.

Even so, this component can be disabled and the car will run almost normally. Problems can arise when measuring pollutant emissions and in the long term; due to the modification, fuel consumption may increase. Engine failures should not occur, but it is certainly a substantial change to how it works, so it is worth thinking carefully about whether this modification is necessary.