The muffler its self isnt restrictive, its the baffle in the end that will get you. If your making a bunch of smoke from hard fueling you will eventually clog it. My friend that has the same set up I do actually clogged his AERO TURBINE 50/50R (5 inch muff with resonator). Yeah we fuel hard to make those big power numbers. GET RID OF THE KITTY all it does is collect and store heat. It is BAD for performance and really bad if your going for big power. You can cook your turbo in a hurry with that guy on.

 

no cat, and 51" Fleetguard here and I have no issues. Love the sound, I have a turn down at the end of the muffler but may add an over axle pipe and side out later.

 

Well, I finished installation of the 51’ Donaldson, replacing my strait pipe. I like the new sound. The Donaldson takes away some of the “raspyness”. It is quieter through the RPM range too, I can make out the turbo more. It still has a nice rumble at idle; no one will mistake your truck for a Prius with this muffler.

Installation wasn’t bad, it fit pretty well. I welded it to the back of the catalytic converter. The end of the muffler landed just before the bend starts in the tailpipe. (I think I have an aftermarket tailpipe. The 1st owner ditched the OEM muffler.)

I cleaned out the catalytic converter while I had it off. There was some soot in there even though I could see through the catalyst material in the middle. The CAT certainly wasn't clogged.

 

Look at the photos here


https://www.dieseltruckresource.com/...ight=donaldson

 

Late addition: I got a Nelson for mine. Part # 86131M. It has two perforated sections at either end and a opening in the center(about a foot's worth) without any material or baffle in it like the Donaldson. See straight through it. The center section reminds me of the Banks muffler I had in the past, with it's expansion area. Should have it on this weekend.

Chris

 

I'd like to know what that Nelson sounds like. Post up after you get it installed.
Wood

 

You got it!!!

Chris

 

Instantly not unhappy. At idle sounds a little deeper, not much more volume. Definately louder running through the gears and pushing it, but not annoying at all. Didn't get any looks or comments from the co-pilot (wife). Throttle is smoother especially on light throttle to increase speed. At 1900 rpm is the only place where drone is present. Don't get me wrong, no drone like a two-chamber flowmaster on a Misstang, but certainly an intrusive noise in the cab. Good thing there's a noise cancelling **** on the dash. Anyhow, Saw-Zall to the old pipes and clamps to hold it all tight. Am going to muffler shop to get hangers made to it. New muffler does weigh less than the old one, but just want the added support. Got the delete pipe from RPM outlet ($58 shipped) and the muffler from my local Cummins ($78 Nelson 86131m) and 4" clamps ($20). Hangers didn't cost anything, but I still gave the guy $20.


Chris

 

I am interested in one of these mufflers. Can anyone explain the difference between the donaldson, nelson and fleetguard? I want the best flow and least noise. What is the recommendation?

 

Just depends on the place you buy it. I had to travel 60 miles to get to a Cummins shop. They had the Nelson in stock. They could order the Fleetgard. The Kenworth shop as well as the Sterling shop in town could get the Donaldson in 2-3 days. All had similar pricing $70-$90. They are all 51" stack mufflers for big rigs. I have had a Donaldsons and Nelsons and noise levels are nearly the same. The Donaldson had the baffle in the center which forced the flow outward and back into the center. The Nelson didn't have any baffle and appeared to have less packing because of the center void area. Just comes down to convienence and level of patience I suppose. My goal was to have the same noise level as stock when it mattered (light cruising with the family or towing, again with the family). Then to have no restriction and lower egt's. Of course at a lower cost than a kit.

Chris

 

Are you saying that they all perform about the same?

 

I just swapped my stock muffer for a direct fit Magnaflow 4" SS muffler. It is prtetty much stock sounding except at 2200 rpm where it is muchg deeper. Overall it looks like the the EGTs are about 100-125 lower while towing. All in all $230 well spent.

 

If you go to this web site you can compare about any muffler you want and make a good decision.

https://dynamic.donaldson.com/webc/W...?section=10210

This site has a lot of good flow info.