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Discussion Starter · #1 ·
I've never been a fan of EGR's especially in diesel applications. I can't stand the thought of all that soot being recirculated. I along with most others believe that the EGR will reduce the engines life.


I asked for information in the ask the techs forum pertaining to the EGR. http://dieselplace.com/forum/forum_posts.asp?TID=12356&PN=1 GMCSID provided me with the information I was looking for. From what I can tell it looks like a stepper motor is used to open the EGR upon the ECM's request and a spring closes the EGR valve when it is not called upon. So my thoughts are that when the engine is off, the EGR is closed. If I am correct, if we unplug the EGR while the engine is not running the EGR should be closed and not be able open under any circumstances short of a spring failure. This would result in an ideal situation of no Exhaust gasses be recirculated at all.


I unplugged my EGR about 600 miles ago to test the results. So far I have no check engine light although I am sure there will be a couple codes set such as insufficient EGR flow etc. Now I can't say for sure but my fuel mileage seems to have improved. I gained about 1.5mpg running empty on one tank. Nothing changed in my driving routine but my truck is still under 2000 miles so it might just be breaking in that brought on the increase. It also seems to have better throttle response resulting from seemingly quicker turbo spool up times. I have no way to measure this so it might just be a figment of my imagination brought on by hopeful thinking. My theory (which is most likely totally wrong) is that there might be a decrease in spool up time resulting from ecm not having to wait for the EGR to close before allowing the turbo to spool up.


Test at your own risk. I am not to be held responsible from any negative side affects or damage that may result.



I might be totally off the wall here. I would really like to hear any opinions, comments or related experiences.
 

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Where the heck is it?--I'll unplug mine too, just to see what happens.
 

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Discussion Starter · #3 ·
By the engine oil dipstick under the intake. It's a round plastic housing with a plug with 5 wires plugged into it.


Here is a basic drawing of it.


 

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Discussion Starter · #4 ·
Please let me know if you see a decrease in turbo spool up times.
 

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I am gonna do this too.....awesome thinking and post max power!
 

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Discussion Starter · #7 ·
Doesn't look like it.
 

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Well, I'm not ready to try it just yet, but I'm definitely interested. Something tells me to wait and see what happens. I think once winter rolls around you will see some codes set off, as you suggest Max Power.


I think it is a good idea, but I will wait and see for a little while. Heck, I've got over 11,000 EGR miles on it now, what can a few more hurt since I'm not putting many miles on it right now.


You could do a rough test on it if you had a G-Tech (or whatever they're called nowadays), or a Friend with a stopwatch. If there is a noticeable difference you should be able to measure it within a tenth or two I would think.


Start with the EGR off, do three runs to 60 MPH (or 100 KpH), then reconnect it, and do the test again. You would probably have to do it on a fairly cold day (do those exist in August?) to see if there is a measurable difference.


I don't like the soot racing around either, so if this turns out good, I'll do it. Hopefully it will work.


Does the EGR work all the time or just until the beast warms up to normal operating temperature? I'm kinda fuzzy on the whole EGR thing.


Thanks,
Dennis
 

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I wonder if the sensor is in that bundle as well. Five wires seems a lot for just a stepper motor. If that is the case, you won't get any codes either.


Dennis
 

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Discussion Starter · #10 ·
I really don't know for sure but I would assume that 4 out of the 5 wires are for the stepper motor and the 5th is likely a stepper motor position sensor. At least that is similar to other stepper motors I have experience with.
 

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I should be able to tell you for sure on the 11th. The Helms tech manual is supposed to show up then.


Dennis
 

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Its quite normal that the trottle response and turbo spool up time improves when disableing the egr. The exhaust gas is no longer "wasted" going back through the egr pipe to the intake. All the exhaust gases are now available driving only the turbocharger. The egr principle is simply like this: A part of the exhaust gases are routed back to the intake and burned again resulting in reduced NOX. The flow is controlled via the PCM depending on load and rpm.

I did remove the egr many years ago on my turbo diesel landcruiser with the same results as MP. Much cleaner intake (the soot from the exhaust no longer reaches there) and quicker response! You also get cleaner exhaust gases with less soot since the dirt is not recirculated all the time but NOX will go up. With egr NOX is far better but soot much worse so there is a trade off, but both values are half way good. Without egr soot will decrease a lot but NOX will go up the same time. I feel for our nature it makes no real difference if I produce lots of soot or lots of NOX, both are bad! But for the intake valves, cleaner burning engine etc. its much better without egr.
Good to know that on a modern engine like the dmax there is still an easy way of improvement thanks MP!
So I will disconnect it as soon I have my truck - I have ordered today my 2500 HD CC SB 4 x 4 GMC in dark blue - can't wait to get it (after waiting more than 3 years...long story!)
 

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Discussion Starter · #13 ·
Update: another 200 miles. Fuel mileage is definately increasing. Finally got to do some city driving. Throtle response is definately a lot better around town. Cruising down the highway with the cruise set at 2000rpm the truck is soooo much queiter. You absolutely can not hear any diesel clatter. The only thing you can here is the turbo. So far, no regrets!
 

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Discussion Starter · #14 ·
baimpala said:
I should be able to tell you for sure on the 11th. The Helms tech manual is supposed to show up then.


Dennis


IF you can scan a wiring schematic of the EGR that would be fantastic! Thanks
 

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I can heare mine ajusting when I'm sitting at idle with the big pipe so I know something is going on. I'm going to try the unplug method. I'll let you know what happens.
 

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hear
 

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<H1 style="MARGIN: auto 0in">DTC P1404</H1>
<A name=ss1-1369752></A>http://service.gm.com/servlets/Blob...84038&mspsdsubkey=3243#ss1-1369752ss1-1369752
<H5 style="MARGIN: auto 0in">Circuit Description</H5>


The engine control <st1:personName>m</st1:personName>odule (ECM) uses the exhaust gas recirculation (EGR) position sensor to deter<st1:personName>m</st1:personName>ine the position of the EGR valve. The ECM sends a reference voltage through the 5-volt reference circuit to the EGR position sensor. The ECM provides a voltage return path for the sensor through the low reference circuit. A variable voltage signal, based on the EGR valve position, is sent fro<st1:personName>m</st1:personName> the sensor to the ECM through the EGR position sensor signal circuit. The ECM co<st1:personName>m</st1:personName>pares the actual EGR position with the desired EGR position when the EGR valve is co<st1:personName>m</st1:personName><st1:personName>m</st1:personName>anded open or closed. If the ECM detects a difference between the learned closed position and the co<st1:personName>m</st1:personName><st1:personName>m</st1:personName>anded closed position for a calibrated a<st1:personName>m</st1:personName>ount of ti<st1:personName>m</st1:personName>e, DTC P1404 sets.
<A name=ss2-1369752></A>http://service.gm.com/servlets/Blob...84038&mspsdsubkey=3243#ss2-1369752ss2-1369752
<H5 style="MARGIN: auto 0in">DTC Descriptor</H5>


This diagnostic procedure supports the following DTC:


DTC P1404 Exhaust Gas Recirculation (EGR) Closed Position Perfor<st1:personName>m</st1:personName>ance
<A name=ss3-1369752></A>http://service.gm.com/servlets/Blob...84038&mspsdsubkey=3243#ss3-1369752ss3-1369752
<H5 style="MARGIN: auto 0in">Conditions for Running the DTC</H5>
<UL =disc>
<LI class=MsoNormal style="MARGIN: 0in 0in 0pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l1 level1 lfo1; tab-stops: list .5in">DTCs P0642 and P0643 are not set. </LI>
<LI class=MsoNormal style="MARGIN: 0in 0in 0pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l1 level1 lfo1; tab-stops: list .5in">The ignition is ON for <st1:personName>m</st1:personName>ore than 0.5 seconds. </LI>
<LI class=MsoNormal style="MAR
 

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socaldieseltech said:
Action Taken When the DTC Sets - California
<UL ="disc">
<LI class=MsoNormal style="MARGIN: 0in 0in 0pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l3 level1 lfo3; tab-stops: list .5in">The control <st1:personName>m</st1:personName>odule illu<st1:personName>m</st1:personName>inates the <st1:personName>m</st1:personName>alfunction indicator la<st1:personName>m</st1:personName>p (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
<LI class=MsoNormal style="MARGIN: 0in 0in 0pt; mso-margin-top-alt: auto; mso-margin-bottom-alt: auto; mso-list: l3 level1 lfo3; tab-stops: list .5in">The control <st1:personName>m</st1:personName>odule records the operating conditions at the ti<st1:personName>m</st1:personName>e the diagnostic fails. The first ti<st1:personName>m</st1:personName>e the diagnostic fails, the control <st1:personName>m</st1:personName>odule stores this infor<st1:personName>m</st1:personName>ation in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control <st1:personName>m</st1:personName>odule records the operating conditions at the ti<st1:personName>m</st1:personName>e of the failure. The control <st1:personName>m</st1:personName>odule writes the operating conditions to the Freeze Fra<st1:personName>m</st1:personName>e and updates the Failure Records.
</LI>[/list]
Sooo... It sounds like the California trucks will illuminate the SES light?? Does storing the information in a different location in the ECM make for a tougher time with the dealer? I would like to unplug, but don't want to create a problem with the dealer if I need warranty work. Any thoughts from the techs?
 

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Discussion Starter · #20 ·
I wouldn't be surprised if California trucks turn on the light when disconnected. It almost sounds like they want us non california users to disconnect it. Why else would they only have cali trucks turn on the MIL?

I wouldn't worry about the dealer. Just tell them you unplugged in once because you thought it was making noise or something. If they see the codes and know why they are there they won't do anything about it IMO.
 
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