triggerman
09-12-2003, 19:19
For all 96 and up L56 trucks. Well, I finally stumbled across a way to get the PCM to STOP feeding the engine a steady diet of exhaust gas. This mod cuts EGR function to about Half the normal rate, with no pesky EGR code! Just cruising along at about 63 and up, the EGR will will stay CLOSED !!! Slower than 63, The EGR will function almost as much as originaly intended . I originaly built this mod to slightly enhance the factory boost. Basicaly, I threaded a 1/4" barb into the cavity under the Manifold air pressure sensor (small black box on top of upper intake manifold). This sensor has a plastic male barb that was shortened slighly on the brass barb side so I could rob some of the manifold pressure there, and transferr that air by way of a 1/4" tube, to a 1/4" barb installed in the air intake tube between the Turbo and the MAF sensor. The turbo builds a slight amount of vacuume out to the back of the MAF. And this helps draw pressure away from the MAP, giveing you about 3 LBs of additional boost. Originaly I had the extra boost air piped into the intake air tube in FRONT of the MAF and the EGR function was unchanged. Now with the extra boost air going back into the engine BEHIND the MAF, the PCM must figure their is not enough incoming air to justify opening the EGR at Hi cruising speed. Also there is now about 5 LBs of steady boost at 65 MPH where there was only about 1 1/2 LBs factory. Since EGR will not be on at hiway speed, I expect a slight bump in MPGs. I am convinced this mod will cut the accumulation of intake manifold sluge drasticaly for the guys that do a lot of Free way cruising. :D