Same old story.... I got a 99 SD f250 with with a 5.4 with a single rear exhaust pipe and a straight pipe. i want to do duals out the back back i was told that without the muffler, i wouldn't have the back pressure and the flow to get a good exhaust note out of the duals, and i wouldn't have any power. Is that true? i really want duals but i hate the thought of a muffler!

any help is appreciated!

 

Yes you need a muffler to have back pressure, you will also need a catalytic converter for both sides.

 

No, you don't need back pressure. That's a total myth. What you need is for the exhaust to be flowing at the highest velocity possible, while having as little back pressue as possible. You don't need mufflers to do this.

 

myth or not, the 5.4 has been known to suffer when guys removed the cats and mufflers

leave the cats installed and run true duals after them. It'll sound fine, and you should see no performance hits

 

That is incorrect, try running straight exhaust with no mufflers, then run it with mufflers and it will run better with more power with back pressure.

I know this 1st hand from when I built my 1st truck.

 

I say forget the duals out the converter except if you are wanting the looks. Mine has 3" pipe which is plenty big enough for the 330 inches of motor you have. Put a performance y pipe on it along with a free flowing muffler and you'll be money ahead with all the gains your going to get without going to a full bore header and true dual system.

 

^^^X2.. ive tried it on a Honda civic an 78 old cutlas and my old 86 GS750 and running with no back pressure didnt work... I seen the time slips and felt the difference big time...

 

Read:

www.mustangevolution.com/forum/f312/t296628/

 

Your better off with a properly sized system with a single in dual out muffler. (3" in dual 2 1/4" out will work well) If you want more sound output just get a smaller capacity muffler.

For "true duals" both pipes would have to run along the passenger side of the truck because the fuel tank gets in the way on the drivers side. I have true duals on my 74' but would never put such a system on my SD.

Probably because your exhaust pipe size was too large. You do not need a certain amount of backpressure, you need proper exhaust velocity.

 

So basically, when im getting from this is get a performance y pipe? i already have gibson shorty headers, and the straight pipe, so with a perf y pipe ill have all the velocity i need, right?