Exhaust Gas Re-circulation occurs during light engine load, it's purpose is to reduce NOx emissions. Hot gases from the exhaust are vented back in to the intake of the engine instead of fresh air with a higher oxygen content. The hot exhaust gas acts in a similar manner to an inert gas under combustion conditions. The slightly inert gas causes a reduced cylinder temperature and also a reduction in peak cylinder pressure. The result of this is that less oxides of Nitrogen are formed during combustion (NOx). This is beneficial for the environment and public health however it does cause a lot of problems for an engine.
The main problem of EGR is that is clogs up the intake manifold and causes lots of soot, this is why DPF filters had to be introduced to diesel vehicles. It’s a system which solved one problem (NOx) and then created another (more particle mass).
Another down side of exhaust gas re-circulation is that there is a slight trade off between fuel economy and NOx emissions. With EGR fitted an engine is actually slightly less efficient. To add to this car manufacturers also retard injection timing slightly as this also helps to reduce NOx. Again this has a negative effect on fuel economy.
In most countries including the UK removing the EGR will make your vehicle illegal for road use. We cannot offer EGR delete to customers who will be using the vehicle on the UK roads.