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Old 08-15-2014, 07:57 PM   #1
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Cummins muffler elimination

I have a 2004 Cross Country with a 5.9 300hp Cummins. I believe this is the ISB. I have seen posts about removing mufflers and installing straight pipe. I am wondering if my engine is one that would benefit from the straight exhaust.

Thanks, Terry
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Old 08-15-2014, 08:05 PM   #2
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Yes, your ISB will benefit
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Old 08-15-2014, 08:13 PM   #3
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Before you do anything, check to see if you have a "straight through" muffler already installed. A recent straight pipe thread had me wondering too so I checked and found Freightliner installed a straight through muffler during manufacture so no need to consider anything on mine. Measure the distance from the tip of the exhaust outlet to the down pipe turn just before the muffler inlet and shove a length of fish tape up the pipe to see how far it will go. You may already be "straight piped" too.
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Old 08-15-2014, 08:16 PM   #4
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Well Sir, first off, in my basic opinion, if I were you, I'd call a Cummins service center or, cruise around on line, for Cummins Diesel pickups. I'm sure there's a dozen or so. There's forums for everything now days. If anyone's got info on how to "hot rod" Cummins engines, it would be them. One more place to call is, Gale Banks Engineering.

You see, Cummins allows for Banks Kits to be installed on their engines, unlike CAT, who does not and, there's no "kits" for it. I have a very good friend who has a '99 Fleetwood Discovery and it has the 275HP Cummins in it and, he installed a Banks kit several years ago. That coach is pretty hard to keep up with. He's real happy with that kit. Our coach is an '04 Itasca Horizon, 36GD with the C-7 330HP CAT and, I cannot keep up with him on grades. He pulls away quite easily.

Anyway, as for a straight pipe, I can't help you on that. I removed my big-a$$ muffler and installed an Aero 5050XL, Stainless Steel, straight through muffler and, I can tell you, it maid almost no difference at all except for the fact that it's about 30% louder now which, I hate. So, your choice Bud.
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Old 08-15-2014, 08:26 PM   #5
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I would examine what kind of muffler you have. It could be a restricted design. Only way is to look into it. There are mufflers available with very little restriction. I run a Aero 5050 pure stainless steel. This means a 5in inlet with a 5in outlet. I bought mine on Ebay for a little over $120.00 delivered. I have a Caterpillar with good response, hard pulling with slightly better boost pressures now. Haven't noticed any better fuel mileage, but thats not what I was looking for.
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