There's been some scattered recent discussion about whether or not doing an EGR mod will eventually plug the CAT. Thought I'd start some feedback here.

At this point I am undecided, but am leaning towards that it will not. IIRC the EGR doesn't function all the time anyways, so the CAT should already be able to handle the added exhaust gases during those times of non-functionality.

Your opinions??

you dont need no stinking cat anyways!!! ):h
mines getting plugged with rainwater and leaves in the backyard!

I too am not sodl on this mod. I am sold on remving the CAT with a 4inch exhasut though(Thanks to kennedy for the dyno truth/proof):)
But, I haven't seen any hard proof that blocking the EGR is a worthwhile mod and I won't have to worry. Where I live I have no emisssions to worry about so droppin the kitty is no big deal. I guess I'll have to go talk to some of the local stealers and see how they feel about mods tothe trucks.

I too am not sodl on this mod. I am sold on remving the CAT with a 4inch exhasut though(Thanks to kennedy for the dyno truth/proof):)
But, I haven't seen any hard proof that blocking the EGR is a worthwhile mod and I won't have to worry. Where I live I have no emisssions to worry about so droppin the kitty is no big deal. I guess I'll have to go talk to some of the local stealers and see how they feel about mods tothe trucks.

I'm sold on the EGR mod. There's no question my truck is performing better with it blocked (for now at least). There are alot of people here running with the EGR mod and only two I can think of that have mentioned that they discontinued it (BigWill21 a while back and Brutis just recently - I'm sure there are more though). Point being - there doesn't seem to be many who re-connect it.

I'm not sold on the fact that the CAT will plug. I also don't want dealer problems by removing it.

Yeah I'm hoping the dealers will be cool with mods. I want to chip this thing soon with no worries about warranty work....but if this truck is anything like my old LB7 I'm not worried:D
I guess my next question is......How much does blocking the egr effect the warm up in the cold mornings? I plug my truck in whenever I can but sometimes I can't and she is a pig even with the high idle and egr etc.:( Just trying to get some info on all this...wish I had the the $$$$ for an exhaust.:bawl:

Thinkmoto,

It's only been down to the mid 30's at night since I did the EGR mod, but I really don't see any noticeable difference in warm-up time. When It gets below 20*F I usually plug it in for about 11/2 hours on a timer.

My guess is that the opposite will happen. With the ERG blocked the intake air will have a higher oxygen content since the exhaust gas are no longer displacing part of the flow. More oxygen means cleaner burn and less soot. I think the converter was added with the EGR to burn off the additional soot created by recirculating the exhaust gases back into the intake.

My guess is that the opposite will happen. With the ERG blocked the intake air will have a higher oxygen content since the exhaust gas are no longer displacing part of the flow. More oxygen means cleaner burn and less soot. I think the converter was added with the EGR to burn off the additional soot created by recirculating the exhaust gases back into the intake.

Interesting theory! Basically, if it's buring cleaner, the CAT is working less!??

I have an 03 with cat, and it was plugged by 40k mi. I noticed a gradual increase in egt's and engine temp, along with degradation in performance. While trying to diagnose it, I blocked the egr, noticed little difference. Finally put 4" exhaust on and removed the cat. Bingo- instant relief! Kinda like a laxative- you run better when yr pipes are cleanhttp://www.dieselplace.com/forum/images/smilies/biggrin.gif...
So, even if you leave it alone, it looks like the cat has a limited life bfore it closes up enough to start showing heat symptoms. My egt's were up 200 deg from normal, and engine temp was at 210 all the time, with the fan running frequently. Now, I'm back down to egt's 500-550 deg at 70-75 cruise, and the engine almost doesn't get warm enough for the juice to engage. Obviously, performance and mileage came back to normal also. My egr is still blocked, I still have the SES light because of that, but I think I'll just live with it and check codes from time to time. I certainly won't put a cat back on....
Steve

Interesting discussion. :rolleyes: I'm one of the guys who disengaged the EGR then plugged it back in. While towing my 5ver the grade braking just didn't seem to work as well with the EGR unplugged. MPG's were never consistently higher or lower, pretty much stayed the same. Turbo spool up did seem faster though. :rolleyes:

Like someone stated earlier the EGR closes at about 205* anyway so it really is only a factor at lower operating temps. Kind of begs the question "How could my grade braking be effected since it should be closed at those times as well?" Is JJ nuts??? Don't answer that! :D
Several LLY owners that have disconnected CAT's threw codes. Seems the LLY's PCM relies upon backpressure to regulate things. I plan to gut my CAT a little with a pipe to increase EG flow but still retain sufficient backpressure to avoid codes. If that doesn't work I'll regroup with another plan! ):h JJ :)

Done some testing watching the VVT position on my truck. If there are EGR codes, the VVT does not seem to get commanded to close all the way. Why? I have no idea. Keep in mind this is only on my truck and I have not had a chance to confirm it on anyone elses.

The EGR function reduces NOx emmisions.

Done some testing watching the VVT position on my truck. If there are EGR codes, the VVT does not seem to get commanded to close all the way. Why? I have no idea. Keep in mind this is only on my truck and I have not had a chance to confirm it on anyone elses.

The EGR function reduces NOx emmisions.

I know this is preliminary but:

#1) R U saying that if there is a DTC code present that it appears that the turbo is commanded to be less effecient? Hence, maybe another reason to run the Stick to keep the codes clear???

#2) "The EGR function reduces NOx emmisions" Doesn't it reduce emmisson levels only because a certain percentage of the NOx gases are re-circulated rather than exiting via the exhaust? If that's the case, then with the EGR blocked, the CAT would be "filtering" more NOx gases then it was made to do, thus increasing the likelyhood that it could clog and throwing the "cleaner burning" theory out the window??

#2) "The EGR function reduces NOx emmisions" Doesn't it reduce emmisson levels only because a certain percentage of the NOx gases are re-circulated rather than exiting via the exhaust? If that's the case, then with the EGR blocked, the CAT would be "filtering" more NOx gases then it was made to do, thus increasing the likelyhood that it could clog and throwing the "cleaner burning" theory out the window??
NOx is reduced by keeping combustion temperatures down. I don't think the converter has anything to do with NOx emmissions. The combustion temperatures are reduced by displacing some of the oxygen in the intake charge with essentially inert exhaust gas. At least that is my understanding of the system.

NOx is reduced by keeping combustion temperatures down. I don't think the converter has anything to do with NOx emmissions. The combustion temperatures are reduced by displacing some of the oxygen in the intake charge with essentially inert exhaust gas. At least that is my understanding of the system.
That is my understanding too.

NOx is reduced by keeping combustion temperatures down. I don't think the converter has anything to do with NOx emmissions. The combustion temperatures are reduced by displacing some of the oxygen in the intake charge with essentially inert exhaust gas. At least that is my understanding of the system.


OK, so. If the EGR system only controls NOx emissions and the CAT has nothing to do with NOx emissions is it safe to state that since the two are dealing with unrelated gases that the CAT should remain uneffected by an EGR mod.?

P.S. - Now we're cooking :)

I know this is preliminary but:

#1) R U saying that if there is a DTC code present that it appears that the turbo is commanded to be less effecient? Hence, maybe another reason to run the Stick to keep the codes clear???

Probably should not have mentioned it since I am only speculating why I am seeing what I am. But....

It appears that the Full Closed vane position can generate very high backpressures while not generating much boost. Kind of like a choking effect. When the engine is building boost, the vanes are positioned just a little more open than full closed. This cracked open position happens with or without the EGR working, but I don't see the full closed when the EGR codes. I am speculating that the cracked open position is the optimum vane position for making boost.

Is that good? Bad? I have no idea right now. Boost seems to build the same in either mode. Watching the VVT work is very interesting though.

So how do you disconnect the EGR system? Just block the butterfly open?

And where does this blocker plate go?? I have tried to go to the pictures and instructions that fingers had in one of his posts of the 64 page EGR discussion but it says the page was unavailable. I know there are 12 mm bolts, but there are quite a few around the egr area.

Fingers, just curious to know what you are using to "watch" the VVT?

Volt meter hooked up to the VVT position sensor.

i am under the impression that all it does is lower egt's to keep less O2 in the engine to keep the NOX to a lower level.