6.7L Cummins Forum

Winger · #21 (**permalink**) 08-08-2008, 10:42 PM

I don't understand is that not a muffler laying next to the 5" exhaust on the ground? The MRBP looks to be the same size as my tail pipe on my 08. On mine I can put my fist into the exhaust tip. Of course not while hot. LOL Here in CA if you take the muffler out you will have to reinstall it when it comes to smog check time or they will ding you, next time it's a check only station, as it is part of the emissions system that they check for.

CumminZ · #22 (**permalink**) 08-09-2008, 12:03 AM

CumminZ · #23 (**permalink**) 08-09-2008, 12:03 AM

Vis-a'-vis · #24 (**permalink**) 08-09-2008, 12:18 PM

Great, are you seeing any MPG gains from towing?

CumminZ · #25 (**permalink**) 08-09-2008, 08:10 PM

This kinda long story. Over the last year since I purchased my 07.5 I have added the 5" MBRP, modified my factory air box to give me cold air and gutted the intake tube and have added 245x19.5s. Early on the truck gave me about 11-13mph while towing heavy. About the 6000 trip to the Rockies in June I added the MP8. For the most part that entire trip I got 9.5mpg. While in CO. I added a ton of CO. red rock. Accended Monarch Pass and on to Petrified Forest and back to NC. still getting 9.5mpg. Within a month of getting home and very little driving my catalyst 90% message appears. I made trip to dealer yesterday and they performed forced regen for 45 miles. Coming back to dealer overhead indicated 14.5mpg. Filled up this morning and drove 77 miles on interstate, filled up back at home and hand calculated 14.3mpg.

There is no doubt in my mind that the MP8 started the DPF problem. It is not for towing heavy.

Squid · #26 (**permalink**) 08-09-2008, 08:43 PM

Your experience with the MP8 is why I nixed the idea of stacking the MP8 with the Edge. Around 15 MPG is right where you should be stock from my experience. I gained 1 mpg when I added the Edge Juice and then another 1 MPG when I added my Volant and I gained another .5 after I cleaned the oxygen sensors a couple of weeks ago. You might want to think about cleaning your oxygen sensors, at least the one in front of the DPF. If your DPF was at 90% full I bet it's pretty sooted up too.

Winger · #27 (**permalink**) 08-09-2008, 09:14 PM

OK I see now, I wonder if you had a piece made up the same length as the muffler and replaced the muffler with it then when it came time for the smog check you could just put the muff back in do the check then start over. It only happens once every two years.

jamespi · #28 (**permalink**) 05-18-2009, 05:10 PM

This thread started a year ago; so now I am wondering has anyone else got rid of the muffler and increased pipe size. If you did was it worth it? What did you use?

Winger · #29 (**permalink**) 05-18-2009, 09:59 PM

Yes I took the stock muff off and put in a magna flow straight through muff. With the Volant I'm now getting 16mpg all around driving. Did 18 today going back a forth to work. Freeway 70-75 cruise EB on. Now when it comes to towing I do 10-11 MPG pulling 12,000 5er. I love the tow haul mode with the EB. I try to stay out of town cause that just kills the fuel MPG. 14.5-15.5MPG

Vis-a'-vis · #30 (**permalink**) 05-19-2009, 07:54 AM

Winger, what does it sound like??

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