AO Platinum Member
Join Date: Feb 2002
Location: The land that Time forgot
The EGR valve opens at high rpms so that some exhaust gas is recirculated back into the combustion chamber. Contrary to logic, this cools the combustion chamber down and prevents it getting so hot that the NOx emissions increase. They tend to get much worse above 1300C..
EGR can cause problems because exhaust gas is a bit manky and gums everything up.
If the ports become clogged this can block the flow altogether or force it all into only a few cylinders, so you get lumpiness. The exhaust gas can also coat the throttle body plate, which can cause a rough idle.
Cleaning the throttle body and the ports is the only way to clear the problem. It is unlikely that the EGR valve itself is not working.
Anyways... to answer the question, if you blank the beast off, the exhaust circuit becomes an non-EGR system. The high pressure "intake" is sucked into the engine and the high pressure exhaust is sucked (if the exhaust is properly engineered) or pushed out the back.
No bullets for Chaingun..