Originally posted by 76GMC1500
That isn't EGR. EGR takes small amounts of exhaust gasses and reinserts them into the intake manifold to help keep combustion temperatures down. What you are thinking of is an intake air heater. No exhaust is actually directed into the air cleaner or your air cleaner would be black with soot within 5 minutes. There is a butterfly valve in the air cleaner that closes when the air cleaner is cold. That means air has to be drawn in through that hose and it is drawn in from around the exhaust manifold where it is very hot. This heats the air inside of the air cleaner to an approximate temperature of 125 degrees F. This allows for leaner fuel/air mixtures and was thought to increase milage slightly as well as reduce NOx emissions because higher intake air temps mean lower combustion temps.
I knew EGR is exzaust gas recirculation, I thought that hose was recirculating gasses, guess not. it could still very well be what the guy is thinking of tho.