Super excited sitting in the waiting area as the are installing my true dual Magnaflow system! Will post pics later once it is done!!

 

You will be happy with it. My neighbor has that same system on his 06 5.4L and it sounds and looks great. Been thinking about doing the SI/SO system on mine.

 

Local muffler shop advises against true duals. Says it screws up the back pressure and every set they have installed loses power. Anyone else heard of this. This comment is the only reason i have not installed true duals.

 

In my opinion true dual is the only way to go. If your going to pipe out your truck, you can go big or go home!
Had mine done the past summer and wouldn't go any other route.

 

There will be little if any difference in backpressure if the cats are left in place.

 

I totally agree here. Using the stock manifolds and cats provides enough backpressure to start with.

 

Untrue, I agree with everyone here. With the stock cats you have more than enough backpressure. When I did my true duals I hade one shop tell me the same thing, I told him he was an idiot and left. If anything, by splitting the pipes up you gain a few horses similar to an x pipe or H pipe.

 

Backpressure doesn't make power, scavenging does. Think about it backpressure is a clog. The quicker exhaust gas escapes the better, so its velocity we are looking for. Each engine combination might require a little different pipe size, design or routing to be efficient.

Not to rant but the term "backpressure" drives me crazy.

 

Hahaha, I agree! I always tell people just think, have you ever seen a race car with cats or mufflers...?
The only reason youd see them on a racecar is for noise control

 

I think most people are concerned with backpressure as it relates to the valvetrain. People think that by pulling the mufflers, the engine will float the valves or something...
Totally not going to happen!
And what's with people saying the exhaust modification will make the truck lose torque? I don't see how opening the exhaust can have any negative impact on hp or torque. Only positive effects! It may be true that the peak hp or torque may shift from a specific range of rpm to another, but it will still be there somewhere. It can't just disappear!

 

Let me interject something. I know this is way different, but I had a 94 Mustang V6. It wasn't super speedy or anything, but it was no slouch either. I decided to buy an A-dapter kit with an H pipe and put a take-off GT exhaust system on the car. She was never the same again, torque was gone, top speed was gone, and she lost what little pep she had. I also had a K&N filter (BTW won't touch those ever again) and a Dremel Tool "CAI" (I was poor), and I believe they contributed to the loss too. Shortly after those mods I the computer starts throwing lean codes on both banks. So to say there is no side effect from free flowing exhaust might be a stretch, however I also think that a custom tune would remedy said problems.

 

I'm glad to get all the feedback. These are exactly the same thoughts I had, however since he was in the exhaust business, very well respected and reputable in our area, and was willing to lose a job in order to advise me against I thought hmmmmm! maybe i better check this out first. Can anyone say that they actually gained anything from it other than sound?

 

Gained a much more positive throttle response on mine. Took away some of that "drive by wire" lag that the 5.4's are known to have. That's without a reset of the accelerator pedal. Still need to do that...

 

I added a CAI and an Edge Evolution programmer then a few months later added a Stainless Magnaflow SI/SO cat back system. The difference in adding the Magnaflow to the mix was this. It could have been two things that I experienced.

1. Either I lost some low end torque, but pedal responsiveness improved, and I had an increase to powercurve in the middle/higher rpm's..
OR
2. Either torque stayed the same or increased with a noticable gain in initial pedal responsiveness and a nice mid/high end rpm power gain.

I feel that I did gain a little power all around with the cat back system. Either way, I am happy. I have plenty of power when towing and as a daily driver.
And when I keep my programmer in performance mode, my truck sounds and feels amazing. The Magnaflow SI/SO is plenty loud if you run a programmer, if not it is just a notch or two louder than stock unless you get on the pedal hard.

 

Not harping on backpressure, there are gains to be made, horsepower, over the stock system. The trick is how to get the exhaust to scavenge efficiently.

A 300hp/220rwhp vehicle will not improve with dual 2 1/2 exhaust. That is more oriented to a 400hp/350rwhp vehicle. But a 220rwhp vehicle will deffinetly improve with headers, 2 1/4 duals and x/h pipe. Yes, the hp/torque band may move up.

The trouble with our community is the lack of data. There are differences in mufflers that are documented, but not much else.

If you have seen the kink in our exhaust between the muffler and cats, that limits the effectiveness of most catbacks. You are basically adding a megaphone after the cat.