My extended warranty just ran out @ 400k, so I figure what the heck. Even if there is no real benefit, the way ISX EGRs have been failing, I'd run with it disconnected just so I don't have to worry about having to repair or replace it.

I religiously track every drop of fuel I buy, so I'll know pretty quickly if it makes a big difference. I can't wait to see how it does when we hit the road in a week.

 

Please post your results. I'm very curious.

 

After a little discussion with my local repair shop, which happens to be a Cummins dealer, I'm rethinking this whole EGR experiment. The service manager at this shop is a no BS kind of guy and would not say something simply because it was contrary to what Cummins wants him to say. While Don (the service manager) agrees that disconnecting the EGR would improve fuel economy and make the engine run cooler, he also answered the question I posed in my first post… it would be bad for the catalyst. He said it might be worth taking a $2000 risk (what a replacement catalyst costs) if fuel went to $4 of $5 a gallon and stayed there, but in his opinion at the current price of fuel, the costs associated with the decreased life of the catalyst would outweigh any cost benefit gained through fuel savings.

 

It has been observed that those with DPF's and such are not candidates for unplugging the EGR. Seems like the results are not good since more of the electronics are talking with each other. Since there is no "catalyst" on a pre '07 engine, it is a non issue. I assume by "catalyst" you meant a DPF. They are not the same thing but oh well. Some are not able to do it for other reasons. We all know that Volvo's will throw a CEL if you just scratch your rear in the wrong way. Seems some with Cummins in Volvo's get CEL and other events when unplugging the EGR. I think there are factors like which software version is in the ECM, which make/model the engine is in, etc that might make for some not being able to put there EGR in "test mode". It's a hit or miss proposition. It just has to be tried to see if it works out.

No experience with DPF's, but on the surface it would seem that a DPF would be better off without EGR. There is less soot generated by eliminating the EGR and therefore it would seem that this would cause fewer regens and cleanings of the DPF. But the engineers have created a nightmare of electronics and interactions going on. I am getting soot levels in my oil that rival those that are running bypass oil filter setups. My last oil sample's soot level was around .2 ppm after 25,000 miles. My oil isn't getting black near as soon as before... almost like when I had a N-14 in the 90's. I can run several thousand miles after an oil change before the oil starts to blacken up.

But from a cost effective standpoint, I am not sure that getting almost 1 mpg better fuel mileage, regardless of fuel price, is not a good thing. And since one has virtually eliminated the EGR and cooler issues on the ISX (especially the pre '07 that had the cooler and EGR on the hot side of the engine), just more rediculous things to not have to replace. I realize that a shop manager has no investment in my truck and therefore, it is not his money heading out the stack. But the shop manager at my dealership has no problem with me doing this to my ISX. He, and the shop foremans, are actually captivated by the results I am getting.

I also understand how some may be a little hesitant in doing this for fear of screwing up. For those, I have no problem if they chose not to. Each one has to live within their own comfort level. I have been known for sticking my neck out and getting whacked with a 2x4. But I still am willing to try some new things. On this issue, it has been a win for me. Probably just dumb luck.

 

Forgot to post how it was recommended to me by a Cummins tech to do the unplug thing...

Let the engine sit long enough to get totally cooled down, preferably overnight. Then turn the key on without starting the engine. Leave the key on for at least 10-15 seconds to make sure the EGR valve stays closed. Then remove the lower 6 o'clock postion plug that pulls out towards the engine block. That is it. Valve remains closed until you happen to plug the EGR back in. There are two plugs going to the EGR, only remove the lower plug. Make sure you tape off the plug and receptacle to keep moisture out.... seems if moisture gets in there, like during a rainstorm, it can throw a mess of fault codes (learned that one on my own).


Results on my ISX in an International 9400i.... before EGR disconnect, mpg average around 6.4 pulling average payload of 38,000 lb. After EGR disconnect, average 7.3 mpg. All pump to pump averages and usually running around 65 mph on the Interstate and doing a lot of two lanes with some good pulls as well. When I can stay out on the interstate and there is a fair amount of easy terrain, the mpgs reach into the high 7's frequently.

 

My 2003 Pete 387 with a C15 motor had a catalytic muffler. It was located in-line with the exhaust between the passenger side fuel tank and the drive shaft. It was told that it was unusual for a 2003 to have the catalytic muffler, since they weren’t phased in and mandated until the ACERT 2004 engines, but I had one anyway on my 2003 for some reason. I know Cummins and Caterpillar vary in their designs, but I would assume that if an ’04 C15 has a catalytic muffler that an ’06 ISX would have one as well. I also know that the service manager at my local Cummins dealer seems to think my truck has some sort of catalyst as well. I didn’t get a chance to talk to the mechanic who normally works on my truck though and the service manager could have thought we have a newer truck (most people think its brand new when they see it). I have to admit that I’m new to Cummins and have only owned Cats in the past, but I think I’m capable of distinguishing a catalyst from a diesel particulate filter.

I will investigate further though and if there is no catalyst or catalytic muffler on the truck then I may go ahead with this little experiment. Even if the truck does have some sort of catalyst and its life is shortened, it still may be worth unplugging the EGR. If doing so were to increase our mpg from the current 6.75 to 7.5, it would mean an extra $7,700 a year in fuel savings (at $2.60 a gallon).

 

Yes.... I have heard some Cats have catalysts. But we are talking about Cummins. No such critter on any Cummins setup. Just the DPF's in '07 and above. Catalyst was not dependent on the truck manufacturer, just the engine manufacturer. All emissions requirements are tied to the engine not the truck. Pre '07 Cat Accerts didn't have an EGR even though all the other brands did. This is also why you can order brand new glider kits from FL (Corando and Columbia) and Pete (386)and put, say, a '98 engine in it if you desire. Perfectly legal (except in CA in 2014). That being said, a catalyst reduces CO levels like they do in cars. EGR reduces NOx and in the process, generates more soot because of the reduced combustion temps. If a EGR engine will not hurt a catalyst, then disabling it should make it last longer (less soot to clog it up). Cat used a catalyst on a lot of Accert engines because they were not using EGR and it made the EPA a happy camper. These issues are why Cat is going out of the truck engine business. They can't get around not using an EGR anymore and the other emissions stuff like they could with the Accert. 2010 requirements just flat made it impractical to continue investing R&D into making truck engines. Cummins and Detroit never used a catalyst as they were both using EGR unlike Cat Accert. They just went to the DPF for '07.

Didn't mean to imply you didn't have the knowledge to distinguish between a catalyst and a DPF. Some others have been known to confuse the two. Since the discussion was about the Cummins, I made the mistake that you might have confused the two. My fault.

 

I talked to my local Cummins dealer's service manager again today when I went down to pay my bill and he is adamant that my truck has a catalytic muffler. It's been a long time since I've been under my truck and I really don't recall seeing one (at least not one that looks like the catalytic muffler on my '03 C15).

I didn’t take your comment about confusing a DPF with an EGR to be a personal affront – after all, you don’t know anything about me. I didn’t realize however that there was wide spread difficulty in distinguishing between the two, as they are so dissimilar in form and function.

On another note, I reevaluated unplugging the EGR, which I thought I’d already done, but after reading your description of which plug to disconnect, I think I may have unplugged the wrong thing. As I’ve mentioned before, I’m kinda lost when it comes to Cummins engines. Caterpillar always provides a comprehensive manual, but Cummins apparently doesn’t do this, as I’ve been told there is no such thing as an ISX manual. Anyway, I thought I knew where the EGR is located and what exactly to unplug, but I may have wrong. After unplugging what I thought was the EGR, the truck seems to run fine, but now the check engine light is on, so I may have to give up until I can be sure just what the heck I’m unplugging.

 

It's real easy to find out, just tell them your vin number, and ask them to look for the price on muffler. My ring at around $2500 each (i have 2)

 

Including a pic of the EGR on the Cummins (2003-2006) it is on the hot side just in front of the turbo. The pic shows tape over the correct plug to remove. The receptacle that it came out of is just above the plug in the picture. Tape both the receptacle and the plug to keep out moisture.