Thats not technically a true dual, but some like blueoval said a few people run it. Magnaflow mufflers are mostly ran for that since they have an internal X pipe.

 

well jim,in the case of my van which weighs in ~9k lbs, i'm concerned with low end torque as i tow ~5,500 lbs every weekend from march to nov.
im running troyer tuning -93 tow during my racing season, winter- 94 max perf.,from the oem 3" compared to my 2.25 ss mandrell bent x piped setup, it's not even a comparison -driiving my 04 with 185 k miles even with stock tuning in comparison to my new 2010's that are empty ,is not even a comparison, even running them side by side -my 04 will walk away from the 9 othe 2004- 2010 vans i own.,i'm all ears if ya want to talk about static pressure, velocity pressure and total pressure on what works on 5.4 modular ford engines in regards to exhaust flow...-phil
btw-my van makes 334 rwftlbs torque at just over 2k rpms- so the proof is in the dyno as well as towing and side by side races.

 

Duals sound better.

 

That's true, but it only works on a symmetrical exhaust layout. Since the pipe on the left will have a longer distance for the gases to escape, the X-pipe equalizes it better. IMO, the H-pipe sounds so much better.

 

Well if you like the sound then go with the duals. I know a lot of guys will disagree but hey JMHO and from years of racing. True duals and opening your exhaust is more for mid to top end in WOT. Even that at times, without the right gearing doesn't help.

Just as an example, a friend of mine I used to race with had a SS Camaro which was running 10.90's had true duals. Just for ****s and giggles he threw on a single Catback exhaust with a Hooker muffler. Hey dropped to into the 10.80s. For you guys that race, once you get into the 10's, it usually takes about 5k to gain a 10th.

I always wonder why truck guys opened up their exhaust and now that I have a truck I wonder even more. Trucks were and still are built for hauling (torque). So by opening your exhaust and losing that back pressure your defeating that, losing low end and will actually have the feel of losing power. Unless your at WOT all the time. Or you have a lot of gearing.

 

As long as you have the correct pipe size, then you will still maintain an optimal amount of velocity. That's what you really want, not so much of a back pressure issue. That's why several members, like myself, have opted for 2.25 inch pipes instead of 2.5 and up. It still maintains good velocity, and in my case, much better than stock or my SIDO 40 I had.

 

an H-pipe wil work on un even exhaust systems, at the minimal power levels most of ya'll are at you should worry about sound...

 

X ftw!

 

h!!

 

x2-unless some one understands sp,vp and tp ,yes by going 2.5" true dual - you will move power band from low to mid top, done right -the bottome gains,especially over 3" siso on a 5.4

 

I already have a Super 44

The bold is what my plan was. I pretty much only drive city now and I don't tow anything since I stopped riding.

I might have to hold off on this until because I'm going to blackout my truck like everyone else :P and this may be the difference between powder coating the stocks or getting monsters.

 

x2....

i just hope adding my long tubes and removing my cats gets ride of my 3/4 ton truck exhaust sound when in boost... If not oh well, but it would be nice.

Power > sound

 

Phil:In my experience, what you get from an exhaust change depends on how good or bad the system you are replacing is versus the system you are replacing it with.

I was very surprised that the the headers and true duals on the Tahoe we tested didn't do more on the stock tune, however when the truck was custom tuned later, of course, it was uncorked and didn't lose anything due to exhaust restriction. It had primary header tubes that were large (1-3/4 IIRC) and dual 2.5 inch pipes.

You made some interesting points, the first being that the 5.4L vans have OE 3-inch exhaust systems. The F-150s have only 2.5-inch systems and I feel hosed!

Second interesting thing is that the Magnaflow system uses dual 2.25s. That's about the equivalent amount of "raw" flow as a 3-inch system but the smaller pipes will help a little more with velocity at low speeds, so it sounds like a well designed system. Many of the dual setups are 2.5 or 3-inch systems which, IMO, are too large for a stockish truck. How do I know about the flow? Here are the flow rates for different sizes of pipes (6-foot lengths) gleaned from the engineering department at Walker muffler.

5-inch: 2200 cfm +
4-inch: 1800 cfm
3.5-inch: 1400 cfm
3-inch: 1200 cfm
2.5-inch: 900 cfm
2.25-inch: 600 cfm


The only exhaust formula I've found that translates well to the "home user"
is this one:

exhaust temp in Fahrenheit + 460
___________________________ x intake airflow cfm = exhaust flow
540

This will give you a static flow rate, which you can compare to the published flow rates of mufflers. Problem is, there are a whole lot of variables. It's difficult to find the flow rates for pipes, for example. I finally got some for length of straight pipe (you saw them above), but they don't account for bends which change the flow rate.

Flow also changes according to exhaust temp. My truck cruises at highway speeds at around 1250 degrees EGT at the exhaust manifolds. At WOT I can see 2000 easy. If you run the calc above for both those temps, you will see greatly different flow numbers.

The other thing, as you alluded, is velocity, which is part of the equation. Given the same volume, smaller pipes have more velocity than larger. As you know, velocity downstream creates inertia, just like a siphon. That delivers a result commonly known as "scavenging" which helps clear the cylinder better. The problem is that it's relative to flow versus pipe sizes, so with every given setup, it's going to be strongest in a certain rpm range. With a big pipe, it will be stronger at the higher rpms. With a smaller pipe, it's stronger at lower speeds. If the pipe is too small, it won't have the flow at the high speed WOT and that reduces upper end power.

But here's the kicker to me! From what I've seen and read, the loss of low rpm performance with with a system that's too large (within reason) is less than the higher rpm loss, or midrange loss, of a system is too small. I think that's why you see so many aftermarket systems that are a little larger for more or less stock trucks than they need to be.

On the other hand, fuel economy is better the closer you can optimize that scavenging to the rpm range in which the truck most often operates. That means smaller pipes and in fooling around with various calculations, the 2.5 diameter is about right in that regard for the 5.4L. The stock muffler is pretty restrictive, but that's easy to change out. Below are the dyno tests results in testing the two systems I mention in the earlier post, plus fuel economy.

Test Data: 2005 Ford F-150 XL 4x4
5.4L 3V V8, automatic, 8,200 GVWR, 4.10:1 axle ratio

Performance Test Data

Condition 0-60(sec.) RWP (hp) RWT(lbs-ft)
(best/av.) (best/av.) (best/av.)

Stock 8.31/8.43 206.6/202.6 252.5/251.5
Muffler Only 8.10/8.15 215.6/215.1 276.4/266.9
Catback 7.89/7.91 224.8/222.6 283.7/278.3


Fuel Economy Test Data

Condition Steady 55 Steady 65 Steady 70 Overall
MPG MPG MPG Average MPG (1)

Stock 17.0 16.5 16.3 15.2
Muffler Only 17.2 16.7 16.5 15.7
Cat Back 17.3 16.7 16.6 15.7

Notes:
1) Mixed situations, approx. 35 percent city, 65 percent rural roads at 60 mph.


In any case, I'm going to have to give that Magnaflow 2.25 true dual system a look! It sound like a way to have a little of both... velocity and high flow.

Sorry, I can't get the chart to stay formatted when I post it.

 

^ where did you copy that out of?

 

Copy what?
As I said, the pipe flow data came from Walker engineering. The dyno and 0-60 data came from the tests I ran on my truck and wrote about in a story on Dynomax exhaust (ORA magazine). The formula came from a Donaldson engineer I spoke with some years back.