Unplugged EGR Valve
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Fleet Mechanic
Joined: Oct 2007
Posts: 1,712
Likes: 18
From: Henderson, NV
Unplugged EGR Valve
For the last 800 miles or so I ran with the EGR Valve unplugged. The most obvious thing I noticed was Boost. With the valve unplugged the highest I could get it to boost was about 25psi. I didn't tow during this time. It seemed more responsive... less turbo lag. No difference in fuel mileage. This morning after I plugged the EGR valve back in I noticed an immediate change in boost as I hit 29 psi with noticeably more power at the high end. I was expecting the exact opposite. Anyone else have similar experiences after they unplugged their EGR Valves?
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Fleet Mechanic
Joined: Oct 2007
Posts: 1,712
Likes: 18
From: Henderson, NV
I thought about unplugging it today and leaving it that way but I don't know what's worse; hot exhaust passing through the EGR Cooler or hot exhaust just sitting inside with no where to go. Until it's blocked off I think I will leave it plugged in.
Lead Driver
Joined: Jun 2007
Posts: 6,757
Likes: 5
From: Corvallis, OR
If you unplug the EGR there is nowhere for the exhaust gases to flow, so less heat will go into the cooler. It will still heat up, but nowhere near as hot as it would get with exhaust flowing through it. Mine has been unplugged since I cleaned the EGR and turbo a few months back, never getting plugged back in.
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Fleet Mechanic
Joined: Oct 2007
Posts: 1,712
Likes: 18
From: Henderson, NV
If you unplug the EGR there is nowhere for the exhaust gases to flow, so less heat will go into the cooler. It will still heat up, but nowhere near as hot as it would get with exhaust flowing through it. Mine has been unplugged since I cleaned the EGR and turbo a few months back, never getting plugged back in.
Lead Driver
Joined: Jul 2007
Posts: 7,868
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From: Rhode Island
Just a theory, but your increase in boost might actually be the exhaust gasses adding additional pressure to the intake?
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Lead Driver
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Mountain Pass
Joined: May 2007
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From: Northern Ontario, Canada
Cheers.
Lead Driver
Joined: Jun 2007
Posts: 6,757
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From: Corvallis, OR
The reason for your boost changes is that when you unplug the EGR, the computer changes programming and the turbo's variable vanes are set to a default position and do not move. Result being higher boost on low end and lower boost up top. When the vanes are allowed to move they can spool the turbo faster and provide higher boost up top. I seen similar numbers on my boost gauge under similar circumstances.
Cheers.
Cheers.
Posting Guru
Joined: Mar 2006
Posts: 1,798
Likes: 2
From: SoCal, SD CO. East
Nope... tttario is correct. The VGT goes into limp-mode for the sake of survival. The PCM depends on signals received from all monitored engine and emissions components. If a major player is disconnected without being removed from the strategy, the PCM responds by trimming the VGT to a static, or limp-mode. Fixed amount of boost across the RPM range.
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Fleet Mechanic
Joined: Oct 2007
Posts: 1,712
Likes: 18
From: Henderson, NV
The reason for your boost changes is that when you unplug the EGR, the computer changes programming and the turbo's variable vanes are set to a default position and do not move. Result being higher boost on low end and lower boost up top. When the vanes are allowed to move they can spool the turbo faster and provide higher boost up top. I seen similar numbers on my boost gauge under similar circumstances.
Cheers.
Cheers.
Elder User
Joined: Dec 2006
Posts: 584
Likes: 0
I have installed a EGR delete which consists of EGR Cooler bypass basically and a new uppipe with blocked of egr. I didnt dissconect my egr valve but i am throughing codes ie. insufficeient gas flow/ recirculation flow low. My guess is the turbo has gone into lymp mode?? and i am not seeing high amout of boost. relly low like 15. it iwill go about 22 going up hill but on striaight away WOT only go to about 18. If turbo has gone into lymp mode how can i change this?? I have a X3 custom tunes with egr bypass i guess the CEL went out but boost is not good? Any suggestions or is my theory correct??
Hotshot
Joined: Dec 2003
Posts: 15,368
Likes: 121
From: Stuttgart, Ar
And if anyone has noticed when cleaning an EGR valve, it takes very little effort to open it by HAND. Enough boost and it will blow open anyway. Unplugging the EGR valve without a delete modification to shut off exhaust to the cooler will cause you nothing but problems. It will still get very hot. The best method is to drive it HARD to try and keep it clean and don't let it idle for extended periods.
and YES......unplugging the EGR valve causes the PCM to go into a default mode which limits boost to the turbo. You've changed operating parameters by unplugging the valve so the computer compensates accordingly.
and YES......unplugging the EGR valve causes the PCM to go into a default mode which limits boost to the turbo. You've changed operating parameters by unplugging the valve so the computer compensates accordingly.
Posting Guru
Joined: Mar 2006
Posts: 1,798
Likes: 2
From: SoCal, SD CO. East
I have installed a EGR delete which consists of EGR Cooler bypass basically and a new uppipe with blocked of egr. I didnt dissconect my egr valve but i am throughing codes ie. insufficeient gas flow/ recirculation flow low. My guess is the turbo has gone into lymp mode?? and i am not seeing high amout of boost. relly low like 15. it iwill go about 22 going up hill but on striaight away WOT only go to about 18. If turbo has gone into lymp mode how can i change this?? I have a X3 custom tunes with egr bypass i guess the CEL went out but boost is not good? Any suggestions or is my theory correct??
Yeah! What Tim said!
And if anyone has noticed when cleaning an EGR valve, it takes very little effort to open it by HAND. Enough boost and it will blow open anyway. Unplugging the EGR valve without a delete modification to shut off exhaust to the cooler will cause you nothing but problems. It will still get very hot. The best method is to drive it HARD to try and keep it clean and don't let it idle for extended periods.
and YES......unplugging the EGR valve causes the PCM to go into a default mode which limits boost to the turbo. You've changed operating parameters by unplugging the valve so the computer compensates accordingly.
and YES......unplugging the EGR valve causes the PCM to go into a default mode which limits boost to the turbo. You've changed operating parameters by unplugging the valve so the computer compensates accordingly.