How restrictive is our stock muffler on the 'O2 Duramaxe? Would it help much, if any at all, to just replace the muffler only? Would it help tone, performance and egt's?

Mine is an 'O2 with edge set on level 4 all the time. Farm and ranch with it so really don't need it loud but need it to pull well (which it does now), always looking for improvements. Used to run a k&n but took it out . . . kinda got skittish about the dirt leaking by.

Thanks much, Doug

Some time back, dmaxallitech (Eric), stated that the stock muffler had a 1.75" preforated s-pipe inside. Just replacing the muffler would be less restrictive and lower egts. Some people around here just run a straight pipe and are happy. Then you could opt to spend from $300 to $1200 for a whole new system. Use the search function and you will find thread after thread about mufflers, exhaust and pipes.

I've tried to keep up over the past year on the exhaust by reading the posts of others. It seems though there aren't that many that just want to keep the original exhaust and just replace the muffler.

I thought about the straight pipe deal but really don't want loud and am scared about the drone problems some have. Just considered dropping that big ole stock muffler for something else but didn't really know if I would gain much except tone.

I removed the muffler and still have the cat, you can hardly tell it's gone other than start-up; it has a neat rumble kind of blast then quiet again. No drone. Perhaps a slight performance gain. Can't tell you about egt's, I don't have gauges. Fuel may be slightly improved but not a whole 1mpg. I am going to try removing the cat next with and without the muffler, all factory size pipes.

If you want improved mileage drill holes or cut out the bottom of you air box per instructions at Kennedy’s diesel web site. That will give you at least 1-mpg increase perhaps more. This is way better than any after market exhaust you could pay for.

FWIW I come from a farming back ground as well (AZ), if you’re not going to replace the filter often, I don't know if I were you if I'd want to do this, only because of the increased dirt entering. It is well filtered this way as good as any, just a lot of volume. Rain could possibly be an issue. Read up on the Kennedy site.

My 2002 just has the muffler, nothing in front of it. From what I've read the cat may smooth out the sound and not make the new motors drone, don't know what mine would do. I wondered if you went straight-pipe and it did drone, why couldn't a guy just weld in a resonator.

I really thought there would be some more people out there that had done this exact thing.

I have straight pipe, no cat, no drone. Only notice how loud it is with the windows down.

I have straight pipe and no cat also. It's just fine unloaded, but drop 12k behind it and it becomes very loud. I just ordered a Spin Tech muffler because I wanted to try something different than what everyone else has.

I kept the Cat, but replaced the muffler with a 4" flow thru. I have lower EGTs and a wonderfully, deep burbling tone at idle. Under load it is noticeably louder, but not objectionable. I notice the benefits most at higher speeds where the engine seems to like the lower backpressure. I don't know if I will see any further benefits by going to a full 4" system now, but because I paid too much for the swap I wish I'd just gone to a 4 incher to start with. That way I wouldn't have any lingering doubts at all.

TC

I run the 3.5" Flowmaster with stock exaust elsewhere and really like it. Sounds great and it is all you need for small power boxes. Cheaper too than complete systems.

Now thats the kinda stuff I wanted to hear about! I knew you guys were out there somewhere.

Hi there,

I have a totally stock exahust system with a freeflowing muffler I picked up at a local shop here in idaho. I really am pleased with it, much better than the straight pipe I had which dronned you outa the cab at 65-70mph. I did notice milage and turbo spoll gains. I like it the way it is right now, I don't run a big enough programmer to worry about egt's too much. Also, I got rid of my K&N too, I'm from a farm in Oregon and really wasn't impressed with the K&N filtering abilities. It got too dirty too fast and was allowing dirt to slip by. I'm with you, it worries me to have that dirt getting through. Hope this helps, good luck!

J-HEFF