Exhaust back pressure

[Erich Zeppelin]

Going to convert my 1999 Expedition with the 5.4L to true dual exhaust. Planing on two new Magnaflow cats and two Magnaflow mufflers, has anyone done research on the optimum set up for this truck? If so, what is the perfect setup? I want what is best for my Expedition not just what sounds good, if that means keeping the stock setup I am willing to do that..........

 

[thenaaks]

The need for exhaust backpressure is a fallacy. What you need to retain is exhaust velocity. If you're wanting to make a bit more horsepower and torque, a true dual setup is probably the incorrect route. A single in/single out cat-back with a free flowing muffler will make a bit more power, as long as you don't go with huge exhaust pipe. The folks at Borla recommended keeping the pipe at 2.5 inches, since these engines don't require huge pipe for maximum exhaust flow. Too much pipe volume will decrease low-mid hp and torque.

 

[Erich Zeppelin]

What about 2 new high flow cats, an x pipe, 2 new Magnaflows (round 6" flow throughs) and dumped before the rear axle?

 

[AbelNavyvet]

Thenaaks you can not be any righter!!!! I to questioned the size of the piping so instead of calling borla, I called magna flow and they recommended a 2.5" piping set up. they really pushed for my to get the entire system cat back and muffler set-up since I already had Gibson ceramic coated headers. they in route to me.

Borla don't make the ATAK muffler for 2nd Gen Expos!!!!! that's the perfect sound to any expedition hands down!!!!!!!

 

[thenaaks]

Erich, sounds like a perfect setup for something making 100 more hp than a stock expy. In my opinion, that setup will cost you low end power, and gain a bit of high end power. Will probably sound amazing! Contact magnaflow and see what they say.

 

[Erich Zeppelin]

Erich, sounds like a perfect setup for something making 100 more hp than a stock expy. In my opinion, that setup will cost you low end power, and gain a bit of high end power. Will probably sound amazing! Contact magnaflow and see what they say.

Well, my engine is stock, 200,000 miles on her, think that set up will still work?

 

[Erich Zeppelin]

Ran into another problem, called Magnaflow and they said I have 4 cats. I told them I only have 2. Just 2, goes like this, exhaust manifold, O2 sensor, cat, O2 sensor, muffler. This set up is factory. Why do I only have 2 cats when everyone says I should have 4?

 

[DetroitDarin]

Re-stating: the perfect set up is NO backpressure. Backpressure isn't good, needed, or wanted. Let that exhaust flow as fast as possible - couple tips: Hot gasses will flow faster, don't go too big on diameter.

As to your truck? I'd trust what you see more than what Mangaflow says. As long as everything measures out right - you should be fine.

 

[AbelNavyvet]

Magna flow has it that Expeditions run equalized at 2.5" piping...