That is the EPR valve,it closes at idle and the EGR valve opens,this increases the pressure to the EGR to help more exhaust get re-burned.(kind of the opposite of how a gas engine EGR works)...its contolled by a vacuum can,that a solenoid tells when to open,combined with the one that operates the EGR valve..
I removed the EPR valve on my 6.2 last summer,when I had to replace (more like invent) new front pipes off the manifolds..
I found out the 45 and 90 degree elbows from parts stores have the ideal bends to fit..that EPR valve has the "donut" gasket tapered seat cast into it,so when I deleted it,I had to make the new elbow pipe have a flat flange on the end to the manifold..
I could have just removed the butterfly and tapped the holes where the shaft was for it,and used bolts to block it off,or welded them shut,but the elbow was the perfect length to work if the valve was simply left off,so I did that instead..(deleting the EPR also raises up the exhaust pipe a bit,which always hung too low ,I thought)..
I used a ball pein hammer to roll the elbow pipe end over and made a flat "bead" about 1/4" thick,by putting it in a vise,with the 3 bolt exhaust flange under it,so I'd have something to hammer against,and I heated it up with the torch..it came out nice!..--then I welded a smaller pipe that fit inside the elbow,that sticks up about 1/2"up into the exhaust manifold,and I just used some red hi temp RTV around the flat area on the pipe--the exhaust manifold has a similar flat area it will but against--so far,no leaks..it fit nice and flat,and the "sleeve" helps keep the hot gases off the flanged area..
I had to use a 45 degree elbow 2-1/4" on the passenger side,and a short straight section--and I think a 2" elbow with a 90 degree bend on the drivers side..
It was a bitch getting those long 3/8" bolts off the exhaust manifold that held on the EPR valve--I heated the manifold white hot several times,still only 2 out of three came out without snapping off--luckily you can get a drill in the drivers side much easier than the other manifold on the passenger side--sucked to drill out though,that bolt was hard as tugnsten,took me several new bits and breaking most of them,and half a day,to get the bolt drilled out and the hole re-tapped..
One of the still red hot bolts dropped right onto my arm when it snapped off too--still have scars that wont ever go away as a reminder of that crappy day..
I noticed a slight increase in power and torque the first time I drove the truck with the EPR removed...I should delete the EGR too,none of the solenoids or other crap has ever been hooked up...
I do have a J code intake,but haven't felt like tackling the job to install it,the fuel injector lines will likely break if I disturb them--it was from a '87 6.2 that snapped the crank,and the engine was dumped upside down in a field and sat there a year or so,before it was offered to me for parts--the intake is completely filled with dirt and pebbles,like cement now--I'd be leery of one stone not coming out if I simply flush it with a hose--hate to see one get inhaled after it was put on,and ruin a cylinder..
I removed the EPR valve on my 6.2 last summer,when I had to replace (more like invent) new front pipes off the manifolds..
I found out the 45 and 90 degree elbows from parts stores have the ideal bends to fit..that EPR valve has the "donut" gasket tapered seat cast into it,so when I deleted it,I had to make the new elbow pipe have a flat flange on the end to the manifold..
I could have just removed the butterfly and tapped the holes where the shaft was for it,and used bolts to block it off,or welded them shut,but the elbow was the perfect length to work if the valve was simply left off,so I did that instead..(deleting the EPR also raises up the exhaust pipe a bit,which always hung too low ,I thought)..
I used a ball pein hammer to roll the elbow pipe end over and made a flat "bead" about 1/4" thick,by putting it in a vise,with the 3 bolt exhaust flange under it,so I'd have something to hammer against,and I heated it up with the torch..it came out nice!..--then I welded a smaller pipe that fit inside the elbow,that sticks up about 1/2"up into the exhaust manifold,and I just used some red hi temp RTV around the flat area on the pipe--the exhaust manifold has a similar flat area it will but against--so far,no leaks..it fit nice and flat,and the "sleeve" helps keep the hot gases off the flanged area..
I had to use a 45 degree elbow 2-1/4" on the passenger side,and a short straight section--and I think a 2" elbow with a 90 degree bend on the drivers side..
It was a bitch getting those long 3/8" bolts off the exhaust manifold that held on the EPR valve--I heated the manifold white hot several times,still only 2 out of three came out without snapping off--luckily you can get a drill in the drivers side much easier than the other manifold on the passenger side--sucked to drill out though,that bolt was hard as tugnsten,took me several new bits and breaking most of them,and half a day,to get the bolt drilled out and the hole re-tapped..
One of the still red hot bolts dropped right onto my arm when it snapped off too--still have scars that wont ever go away as a reminder of that crappy day..
I noticed a slight increase in power and torque the first time I drove the truck with the EPR removed...I should delete the EGR too,none of the solenoids or other crap has ever been hooked up...
I do have a J code intake,but haven't felt like tackling the job to install it,the fuel injector lines will likely break if I disturb them--it was from a '87 6.2 that snapped the crank,and the engine was dumped upside down in a field and sat there a year or so,before it was offered to me for parts--the intake is completely filled with dirt and pebbles,like cement now--I'd be leery of one stone not coming out if I simply flush it with a hose--hate to see one get inhaled after it was put on,and ruin a cylinder..
