So I just had all new SI/SO 3" exhaust run from my cats back on my 06 5.4L. I went with the Flowmaster 40 Series because I just prefer the sound. This isn't a thread about Flowmaster vs. some other kind of muffler so don't give me your opinions on that, I just want to know if 3 inch pipe was too big? I've noticed a decrease in low end tq but it has the nice deep rumble I was looking for, and it sounds awesome!

Question is, is 3" intermediate/tailpipe too big for SI/SO application on this truck? Am I gonna hurt anything running it like this?

 

I guess I should rephrase this post..

I know that with a si/so setup, 3 inch pipe is the way to go to get any noticable performance gains. I guess what I'm wondering is, has anyone else run 3" back from the cats and noticed any gains or decreases in power?

I'm thinkin losing low end is in my head because the truck is running great, it doesn't downshift nearly as much as it did with the stock 2.5" pipe

 

3" single is the right size to maintain decent velocity and scavenging throughout the power band. Some of the low end may be placebo and some may be from the chambered muffler. You put it in for sound and you're happy with it so just have fun with it and don't dwell on it too much.

 

Thanks otto, I'm more than happy with it. I just have some "experts" saying that I shouldn't have gone 3" cause that's why I've got no low end, when I know from my own experience 3" is the way to go. I really do think its all in my head, I guess that's what happens when people start putting in their own $.02! But trust me, I'm def lovin' it!

 

if you have to put the word expert in quotations when your talking about someone, that person is not a expert.

 

Yeah I was being a smart ***, I'm glad someone caught my sarcasm! Just a know-it-all more than an expert..

 

how's the inside drone with the 40 series? thinkin' of the exact same set up, 3" si/so

 

It's not that bad at all. I usually tach around 2200rpm at 70-75mph and it sounds about stock. You get a real nice low end rumble but when you get up in the rpm's it just sounds healthy. I didn't want obnoxious loud but I wanted it to sound good and this is exactly what I was looking for.

 

awesome thanks! i used to have a 50 series with 3" on my jeep and loved it. I truly think the 5.4 needs 3" to "breathe"

 

I agree, 3" is the way to go with a si/so, just don't listen to people who try to tell you that you can only run 3" pipe if you have a turbo or supercharger lol