I think it is a combination of reasons. One reason is because other modifications remove the EGR, such as aftermarket headers or intakes. Another common reason might be for simplicity. Most people don't how the EGR works, so they assume it somehow hurts performance, or adds unnecessary complexity.
The EGR only allows flow during part throttle loads, and can increase your fuel mileage, and of course reduce emissions. When the exhaust gasses are introduced, the susceptibility to knock is reduced.... so when the EGR is functioning, extra timing can be added which gives better throttle response and improved gas mileage. In my opinion, leave the EGR on and functioning unless you have a good reason for removing it.
Yeah... I did not think about that fact that some mods would remove it...
I just see alot of people wanting to turn it off when they custom tune a vehicle and the tuner I brought mine to wanted to as well. I told him not to for the reasons you listed in the above post. I just thought it was weird that I saw so many wanting to shut it off.
To my understanding there is no performance gain. However, I just did a Intake manifold swap and I was very surprised at the amount of carbon and gunk on the inside of my intake and the intake heads. I scrubbed for a good 45 minutes with a wire brush getting it all off. It runs a heck of a lot smoother now and I'm thinking it was because EGR recirculates the exhaust back into the intake. Here is a picture of it. So, wouldnt removing the EGR keep your engine cleaner? http://i1112.photobucket.com/albums/k495/jkjones20059/2010-12-09_21-31-37_459.jpg
To my understanding there is no performance gain. However, I just did a Intake manifold swap and I was very surprised at the amount of carbon and gunk on the inside of my intake and the intake heads. I scrubbed for a good 45 minutes with a wire brush getting it all off. It runs a heck of a lot smoother now and I'm thinking it was because EGR recirculates the exhaust back into the intake. Here is a picture of it. So, wouldnt removing the EGR keep your engine cleaner?
+1, it would seem as though turning off the EGR and using a PCV pre-filter and even a catch can would reduce the amount of carbon re-entering the engine, therefore keeping it cleaner. I'm sure deleting the EGR does not help fuel economy though, but it could keep deposits from forming on the interior of the engine.
The thin film of goop the EGR system leaves on the intake ports doesn't hinder flow in any substantive way. It's too thin and too evenly deposited to be a concern. And on port injection engines the port bowl and back of the valve are cleaned by the fuel injector anyway.
EGR allows the use of increased advance at part-throttle which is good for fuel economy. It reduces combustion temps which is good for reducing NOx emissions. And it's deactivated at WOT and idle. It's really transparent. I don't see the benefit of turning it off.
Most people incorrect,y associate it with a smog device that robs horsepowe...which is untrue.
I commonly see on the fox boards cases where guys with stock cars delete their erg thinking they gained 10hp and then complain why daily driver has lost fuel economy
I run chevron with Techron in all my cars and it does an excellent job at keeping the intake ports clean. I had 37,000 miles on the heads when i recently swapped my intake. my intake ports were as clean as the day i put the heads on. If you don't want to buy chevron fuel then once a year go to the chevron station and buy a bottle of concentrated techron. Poor it in the gas tank and it will clean the injectors along with the heads . It will even partially clean the intake from the sray being in a vapor. Most of those other fuel additives are snake oil and don't work but techron is very good and works very well.
As for the Egr- yea keep it. The benefits far out weigh the negatives.