As I understand it some of the exhaust gases as recirculated back into the inlet manifold at certain times. This has several effects:
Reduces the amount of combustible mixture drawn into the cylinders
Heats the inlet charge, thus reducing charge density, thus reducing potency of the inlet charge
It can increase fuel economy
A few others that I cannot remember at the moment pis..
The idea is that this system can be used to reduce emissions at certain times. However the system was designed to pass stricter tests than the MOT, so you can block it off without worrying thumbup
I'm sure someone will be along to correct me on certain aspects but I believe this is the gist of it notsure.gif
